trigger.c

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/*-------------------------------------------------------------------------
 *
 * trigger.c
 *    PostgreSQL TRIGGERs support code.
 *
 * Portions Copyright (c) 1996-2016, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * IDENTIFICATION
 *    src/backend/commands/trigger.c
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"

#include "access/genam.h"
#include "access/heapam.h"
#include "access/sysattr.h"
#include "access/htup_details.h"
#include "access/xact.h"
#include "catalog/catalog.h"
#include "catalog/dependency.h"
#include "catalog/indexing.h"
#include "catalog/objectaccess.h"
#include "catalog/pg_constraint.h"
#include "catalog/pg_constraint_fn.h"
#include "catalog/pg_proc.h"
#include "catalog/pg_trigger.h"
#include "catalog/pg_type.h"
#include "commands/dbcommands.h"
#include "commands/defrem.h"
#include "commands/trigger.h"
#include "executor/executor.h"
#include "miscadmin.h"
#include "nodes/bitmapset.h"
#include "nodes/makefuncs.h"
#include "optimizer/clauses.h"
#include "optimizer/var.h"
#include "parser/parse_clause.h"
#include "parser/parse_collate.h"
#include "parser/parse_func.h"
#include "parser/parse_relation.h"
#include "parser/parsetree.h"
#include "pgstat.h"
#include "rewrite/rewriteManip.h"
#include "storage/bufmgr.h"
#include "storage/lmgr.h"
#include "tcop/utility.h"
#include "utils/acl.h"
#include "utils/builtins.h"
#include "utils/bytea.h"
#include "utils/fmgroids.h"
#include "utils/inval.h"
#include "utils/lsyscache.h"
#include "utils/memutils.h"
#include "utils/rel.h"
#include "utils/snapmgr.h"
#include "utils/syscache.h"
#include "utils/tqual.h"
#include "utils/tuplestore.h"


/* GUC variables */
int         SessionReplicationRole = SESSION_REPLICATION_ROLE_ORIGIN;

/* How many levels deep into trigger execution are we? */
static int  MyTriggerDepth = 0;

/*
 * Note that similar macros also exist in executor/execMain.c.  There does not
 * appear to be any good header to put them into, given the structures that
 * they use, so we let them be duplicated.  Be sure to update all if one needs
 * to be changed, however.
 */
#define GetUpdatedColumns(relinfo, estate) \
    (rt_fetch((relinfo)->ri_RangeTableIndex, (estate)->es_range_table)->updatedCols)

/* Local function prototypes */
static void ConvertTriggerToFK(CreateTrigStmt *stmt, Oid funcoid);
static void SetTriggerFlags(TriggerDesc *trigdesc, Trigger *trigger);
static HeapTuple GetTupleForTrigger(EState *estate,
                   EPQState *epqstate,
                   ResultRelInfo *relinfo,
                   ItemPointer tid,
                   LockTupleMode lockmode,
                   TupleTableSlot **newSlot);
static bool TriggerEnabled(EState *estate, ResultRelInfo *relinfo,
               Trigger *trigger, TriggerEvent event,
               Bitmapset *modifiedCols,
               HeapTuple oldtup, HeapTuple newtup);
static HeapTuple ExecCallTriggerFunc(TriggerData *trigdata,
                    int tgindx,
                    FmgrInfo *finfo,
                    Instrumentation *instr,
                    MemoryContext per_tuple_context);
static void AfterTriggerSaveEvent(EState *estate, ResultRelInfo *relinfo,
                      int event, bool row_trigger,
                      HeapTuple oldtup, HeapTuple newtup,
                      List *recheckIndexes, Bitmapset *modifiedCols);
static void AfterTriggerEnlargeQueryState(void);


/*
 * Create a trigger.  Returns the address of the created trigger.
 *
 * queryString is the source text of the CREATE TRIGGER command.
 * This must be supplied if a whenClause is specified, else it can be NULL.
 *
 * relOid, if nonzero, is the relation on which the trigger should be
 * created.  If zero, the name provided in the statement will be looked up.
 *
 * refRelOid, if nonzero, is the relation to which the constraint trigger
 * refers.  If zero, the constraint relation name provided in the statement
 * will be looked up as needed.
 *
 * constraintOid, if nonzero, says that this trigger is being created
 * internally to implement that constraint.  A suitable pg_depend entry will
 * be made to link the trigger to that constraint.  constraintOid is zero when
 * executing a user-entered CREATE TRIGGER command.  (For CREATE CONSTRAINT
 * TRIGGER, we build a pg_constraint entry internally.)
 *
 * indexOid, if nonzero, is the OID of an index associated with the constraint.
 * We do nothing with this except store it into pg_trigger.tgconstrindid.
 *
 * If isInternal is true then this is an internally-generated trigger.
 * This argument sets the tgisinternal field of the pg_trigger entry, and
 * if TRUE causes us to modify the given trigger name to ensure uniqueness.
 *
 * When isInternal is not true we require ACL_TRIGGER permissions on the
 * relation, as well as ACL_EXECUTE on the trigger function.  For internal
 * triggers the caller must apply any required permission checks.
 *
 * Note: can return InvalidObjectAddress if we decided to not create a trigger
 * at all, but a foreign-key constraint.  This is a kluge for backwards
 * compatibility.
 */
ObjectAddress
CreateTrigger(CreateTrigStmt *stmt, const char *queryString,
              Oid relOid, Oid refRelOid, Oid constraintOid, Oid indexOid,
              bool isInternal)
{
    int16       tgtype;
    int         ncolumns;
    int16      *columns;
    int2vector *tgattr;
    Node       *whenClause;
    List       *whenRtable;
    char       *qual;
    Datum       values[Natts_pg_trigger];
    bool        nulls[Natts_pg_trigger];
    Relation    rel;
    AclResult   aclresult;
    Relation    tgrel;
    SysScanDesc tgscan;
    ScanKeyData key;
    Relation    pgrel;
    HeapTuple   tuple;
    Oid         fargtypes[1];   /* dummy */
    Oid         funcoid;
    Oid         funcrettype;
    Oid         trigoid;
    char        internaltrigname[NAMEDATALEN];
    char       *trigname;
    Oid         constrrelid = InvalidOid;
    ObjectAddress myself,
                referenced;

    if (OidIsValid(relOid))
        rel = heap_open(relOid, ShareRowExclusiveLock);
    else
        rel = heap_openrv(stmt->relation, ShareRowExclusiveLock);

    /*
     * Triggers must be on tables or views, and there are additional
     * relation-type-specific restrictions.
     */
    if (rel->rd_rel->relkind == RELKIND_RELATION)
    {
        /* Tables can't have INSTEAD OF triggers */
        if (stmt->timing != TRIGGER_TYPE_BEFORE &&
            stmt->timing != TRIGGER_TYPE_AFTER)
            ereport(ERROR,
                    (errcode(ERRCODE_WRONG_OBJECT_TYPE),
                     errmsg("\"%s\" is a table",
                            RelationGetRelationName(rel)),
                     errdetail("Tables cannot have INSTEAD OF triggers.")));
    }
    else if (rel->rd_rel->relkind == RELKIND_VIEW)
    {
        /*
         * Views can have INSTEAD OF triggers (which we check below are
         * row-level), or statement-level BEFORE/AFTER triggers.
         */
        if (stmt->timing != TRIGGER_TYPE_INSTEAD && stmt->row)
            ereport(ERROR,
                    (errcode(ERRCODE_WRONG_OBJECT_TYPE),
                     errmsg("\"%s\" is a view",
                            RelationGetRelationName(rel)),
                     errdetail("Views cannot have row-level BEFORE or AFTER triggers.")));
        /* Disallow TRUNCATE triggers on VIEWs */
        if (TRIGGER_FOR_TRUNCATE(stmt->events))
            ereport(ERROR,
                    (errcode(ERRCODE_WRONG_OBJECT_TYPE),
                     errmsg("\"%s\" is a view",
                            RelationGetRelationName(rel)),
                     errdetail("Views cannot have TRUNCATE triggers.")));
    }
    else if (rel->rd_rel->relkind == RELKIND_FOREIGN_TABLE)
    {
        if (stmt->timing != TRIGGER_TYPE_BEFORE &&
            stmt->timing != TRIGGER_TYPE_AFTER)
            ereport(ERROR,
                    (errcode(ERRCODE_WRONG_OBJECT_TYPE),
                     errmsg("\"%s\" is a foreign table",
                            RelationGetRelationName(rel)),
              errdetail("Foreign tables cannot have INSTEAD OF triggers.")));

        if (TRIGGER_FOR_TRUNCATE(stmt->events))
            ereport(ERROR,
                    (errcode(ERRCODE_WRONG_OBJECT_TYPE),
                     errmsg("\"%s\" is a foreign table",
                            RelationGetRelationName(rel)),
                errdetail("Foreign tables cannot have TRUNCATE triggers.")));

        if (stmt->isconstraint)
            ereport(ERROR,
                    (errcode(ERRCODE_WRONG_OBJECT_TYPE),
                     errmsg("\"%s\" is a foreign table",
                            RelationGetRelationName(rel)),
              errdetail("Foreign tables cannot have constraint triggers.")));
    }
    else
        ereport(ERROR,
                (errcode(ERRCODE_WRONG_OBJECT_TYPE),
                 errmsg("\"%s\" is not a table or view",
                        RelationGetRelationName(rel))));

    if (!allowSystemTableMods && IsSystemRelation(rel))
        ereport(ERROR,
                (errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
                 errmsg("permission denied: \"%s\" is a system catalog",
                        RelationGetRelationName(rel))));

    if (stmt->isconstraint)
    {
        /*
         * We must take a lock on the target relation to protect against
         * concurrent drop.  It's not clear that AccessShareLock is strong
         * enough, but we certainly need at least that much... otherwise, we
         * might end up creating a pg_constraint entry referencing a
         * nonexistent table.
         */
        if (OidIsValid(refRelOid))
        {
            LockRelationOid(refRelOid, AccessShareLock);
            constrrelid = refRelOid;
        }
        else if (stmt->constrrel != NULL)
            constrrelid = RangeVarGetRelid(stmt->constrrel, AccessShareLock,
                                           false);
    }

    /* permission checks */
    if (!isInternal)
    {
        aclresult = pg_class_aclcheck(RelationGetRelid(rel), GetUserId(),
                                      ACL_TRIGGER);
        if (aclresult != ACLCHECK_OK)
            aclcheck_error(aclresult, ACL_KIND_CLASS,
                           RelationGetRelationName(rel));

        if (OidIsValid(constrrelid))
        {
            aclresult = pg_class_aclcheck(constrrelid, GetUserId(),
                                          ACL_TRIGGER);
            if (aclresult != ACLCHECK_OK)
                aclcheck_error(aclresult, ACL_KIND_CLASS,
                               get_rel_name(constrrelid));
        }
    }

    /* Compute tgtype */
    TRIGGER_CLEAR_TYPE(tgtype);
    if (stmt->row)
        TRIGGER_SETT_ROW(tgtype);
    tgtype |= stmt->timing;
    tgtype |= stmt->events;

    /* Disallow ROW-level TRUNCATE triggers */
    if (TRIGGER_FOR_ROW(tgtype) && TRIGGER_FOR_TRUNCATE(tgtype))
        ereport(ERROR,
                (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                 errmsg("TRUNCATE FOR EACH ROW triggers are not supported")));

    /* INSTEAD triggers must be row-level, and can't have WHEN or columns */
    if (TRIGGER_FOR_INSTEAD(tgtype))
    {
        if (!TRIGGER_FOR_ROW(tgtype))
            ereport(ERROR,
                    (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                     errmsg("INSTEAD OF triggers must be FOR EACH ROW")));
        if (stmt->whenClause)
            ereport(ERROR,
                    (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                 errmsg("INSTEAD OF triggers cannot have WHEN conditions")));
        if (stmt->columns != NIL)
            ereport(ERROR,
                    (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                     errmsg("INSTEAD OF triggers cannot have column lists")));
    }

    /*
     * Parse the WHEN clause, if any
     */
    if (stmt->whenClause)
    {
        ParseState *pstate;
        RangeTblEntry *rte;
        List       *varList;
        ListCell   *lc;

        /* Set up a pstate to parse with */
        pstate = make_parsestate(NULL);
        pstate->p_sourcetext = queryString;

        /*
         * Set up RTEs for OLD and NEW references.
         *
         * 'OLD' must always have varno equal to 1 and 'NEW' equal to 2.
         */
        rte = addRangeTableEntryForRelation(pstate, rel,
                                            makeAlias("old", NIL),
                                            false, false);
        addRTEtoQuery(pstate, rte, false, true, true);
        rte = addRangeTableEntryForRelation(pstate, rel,
                                            makeAlias("new", NIL),
                                            false, false);
        addRTEtoQuery(pstate, rte, false, true, true);

        /* Transform expression.  Copy to be sure we don't modify original */
        whenClause = transformWhereClause(pstate,
                                          copyObject(stmt->whenClause),
                                          EXPR_KIND_TRIGGER_WHEN,
                                          "WHEN");
        /* we have to fix its collations too */
        assign_expr_collations(pstate, whenClause);

        /*
         * Check for disallowed references to OLD/NEW.
         *
         * NB: pull_var_clause is okay here only because we don't allow
         * subselects in WHEN clauses; it would fail to examine the contents
         * of subselects.
         */
        varList = pull_var_clause(whenClause, 0);
        foreach(lc, varList)
        {
            Var        *var = (Var *) lfirst(lc);

            switch (var->varno)
            {
                case PRS2_OLD_VARNO:
                    if (!TRIGGER_FOR_ROW(tgtype))
                        ereport(ERROR,
                                (errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
                                 errmsg("statement trigger's WHEN condition cannot reference column values"),
                                 parser_errposition(pstate, var->location)));
                    if (TRIGGER_FOR_INSERT(tgtype))
                        ereport(ERROR,
                                (errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
                                 errmsg("INSERT trigger's WHEN condition cannot reference OLD values"),
                                 parser_errposition(pstate, var->location)));
                    /* system columns are okay here */
                    break;
                case PRS2_NEW_VARNO:
                    if (!TRIGGER_FOR_ROW(tgtype))
                        ereport(ERROR,
                                (errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
                                 errmsg("statement trigger's WHEN condition cannot reference column values"),
                                 parser_errposition(pstate, var->location)));
                    if (TRIGGER_FOR_DELETE(tgtype))
                        ereport(ERROR,
                                (errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
                                 errmsg("DELETE trigger's WHEN condition cannot reference NEW values"),
                                 parser_errposition(pstate, var->location)));
                    if (var->varattno < 0 && TRIGGER_FOR_BEFORE(tgtype))
                        ereport(ERROR,
                                (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                                 errmsg("BEFORE trigger's WHEN condition cannot reference NEW system columns"),
                                 parser_errposition(pstate, var->location)));
                    break;
                default:
                    /* can't happen without add_missing_from, so just elog */
                    elog(ERROR, "trigger WHEN condition cannot contain references to other relations");
                    break;
            }
        }

        /* we'll need the rtable for recordDependencyOnExpr */
        whenRtable = pstate->p_rtable;

        qual = nodeToString(whenClause);

        free_parsestate(pstate);
    }
    else
    {
        whenClause = NULL;
        whenRtable = NIL;
        qual = NULL;
    }

    /*
     * Find and validate the trigger function.
     */
    funcoid = LookupFuncName(stmt->funcname, 0, fargtypes, false);
    if (!isInternal)
    {
        aclresult = pg_proc_aclcheck(funcoid, GetUserId(), ACL_EXECUTE);
        if (aclresult != ACLCHECK_OK)
            aclcheck_error(aclresult, ACL_KIND_PROC,
                           NameListToString(stmt->funcname));
    }
    funcrettype = get_func_rettype(funcoid);
    if (funcrettype != TRIGGEROID)
    {
        /*
         * We allow OPAQUE just so we can load old dump files.  When we see a
         * trigger function declared OPAQUE, change it to TRIGGER.
         */
        if (funcrettype == OPAQUEOID)
        {
            ereport(WARNING,
                    (errmsg("changing return type of function %s from \"opaque\" to \"trigger\"",
                            NameListToString(stmt->funcname))));
            SetFunctionReturnType(funcoid, TRIGGEROID);
        }
        else
            ereport(ERROR,
                    (errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
                     errmsg("function %s must return type %s",
                            NameListToString(stmt->funcname), "trigger")));
    }

    /*
     * If the command is a user-entered CREATE CONSTRAINT TRIGGER command that
     * references one of the built-in RI_FKey trigger functions, assume it is
     * from a dump of a pre-7.3 foreign key constraint, and take steps to
     * convert this legacy representation into a regular foreign key
     * constraint.  Ugly, but necessary for loading old dump files.
     */
    if (stmt->isconstraint && !isInternal &&
        list_length(stmt->args) >= 6 &&
        (list_length(stmt->args) % 2) == 0 &&
        RI_FKey_trigger_type(funcoid) != RI_TRIGGER_NONE)
    {
        /* Keep lock on target rel until end of xact */
        heap_close(rel, NoLock);

        ConvertTriggerToFK(stmt, funcoid);

        return InvalidObjectAddress;
    }

    /*
     * If it's a user-entered CREATE CONSTRAINT TRIGGER command, make a
     * corresponding pg_constraint entry.
     */
    if (stmt->isconstraint && !OidIsValid(constraintOid))
    {
        /* Internal callers should have made their own constraints */
        Assert(!isInternal);
        constraintOid = CreateConstraintEntry(stmt->trigname,
                                              RelationGetNamespace(rel),
                                              CONSTRAINT_TRIGGER,
                                              stmt->deferrable,
                                              stmt->initdeferred,
                                              true,
                                              RelationGetRelid(rel),
                                              NULL,     /* no conkey */
                                              0,
                                              InvalidOid,       /* no domain */
                                              InvalidOid,       /* no index */
                                              InvalidOid,       /* no foreign key */
                                              NULL,
                                              NULL,
                                              NULL,
                                              NULL,
                                              0,
                                              ' ',
                                              ' ',
                                              ' ',
                                              NULL,     /* no exclusion */
                                              NULL,     /* no check constraint */
                                              NULL,
                                              NULL,
                                              true,     /* islocal */
                                              0,        /* inhcount */
                                              true,     /* isnoinherit */
                                              isInternal);      /* is_internal */
    }

    /*
     * Generate the trigger's OID now, so that we can use it in the name if
     * needed.
     */
    tgrel = heap_open(TriggerRelationId, RowExclusiveLock);

    trigoid = GetNewOid(tgrel);

    /*
     * If trigger is internally generated, modify the provided trigger name to
     * ensure uniqueness by appending the trigger OID.  (Callers will usually
     * supply a simple constant trigger name in these cases.)
     */
    if (isInternal)
    {
        snprintf(internaltrigname, sizeof(internaltrigname),
                 "%s_%u", stmt->trigname, trigoid);
        trigname = internaltrigname;
    }
    else
    {
        /* user-defined trigger; use the specified trigger name as-is */
        trigname = stmt->trigname;
    }

    /*
     * Scan pg_trigger for existing triggers on relation.  We do this only to
     * give a nice error message if there's already a trigger of the same
     * name.  (The unique index on tgrelid/tgname would complain anyway.) We
     * can skip this for internally generated triggers, since the name
     * modification above should be sufficient.
     *
     * NOTE that this is cool only because we have ShareRowExclusiveLock on
     * the relation, so the trigger set won't be changing underneath us.
     */
    if (!isInternal)
    {
        ScanKeyInit(&key,
                    Anum_pg_trigger_tgrelid,
                    BTEqualStrategyNumber, F_OIDEQ,
                    ObjectIdGetDatum(RelationGetRelid(rel)));
        tgscan = systable_beginscan(tgrel, TriggerRelidNameIndexId, true,
                                    NULL, 1, &key);
        while (HeapTupleIsValid(tuple = systable_getnext(tgscan)))
        {
            Form_pg_trigger pg_trigger = (Form_pg_trigger) GETSTRUCT(tuple);

            if (namestrcmp(&(pg_trigger->tgname), trigname) == 0)
                ereport(ERROR,
                        (errcode(ERRCODE_DUPLICATE_OBJECT),
                  errmsg("trigger \"%s\" for relation \"%s\" already exists",
                         trigname, RelationGetRelationName(rel))));
        }
        systable_endscan(tgscan);
    }

    /*
     * Build the new pg_trigger tuple.
     */
    memset(nulls, false, sizeof(nulls));

    values[Anum_pg_trigger_tgrelid - 1] = ObjectIdGetDatum(RelationGetRelid(rel));
    values[Anum_pg_trigger_tgname - 1] = DirectFunctionCall1(namein,
                                                  CStringGetDatum(trigname));
    values[Anum_pg_trigger_tgfoid - 1] = ObjectIdGetDatum(funcoid);
    values[Anum_pg_trigger_tgtype - 1] = Int16GetDatum(tgtype);
    values[Anum_pg_trigger_tgenabled - 1] = CharGetDatum(TRIGGER_FIRES_ON_ORIGIN);
    values[Anum_pg_trigger_tgisinternal - 1] = BoolGetDatum(isInternal);
    values[Anum_pg_trigger_tgconstrrelid - 1] = ObjectIdGetDatum(constrrelid);
    values[Anum_pg_trigger_tgconstrindid - 1] = ObjectIdGetDatum(indexOid);
    values[Anum_pg_trigger_tgconstraint - 1] = ObjectIdGetDatum(constraintOid);
    values[Anum_pg_trigger_tgdeferrable - 1] = BoolGetDatum(stmt->deferrable);
    values[Anum_pg_trigger_tginitdeferred - 1] = BoolGetDatum(stmt->initdeferred);

    if (stmt->args)
    {
        ListCell   *le;
        char       *args;
        int16       nargs = list_length(stmt->args);
        int         len = 0;

        foreach(le, stmt->args)
        {
            char       *ar = strVal(lfirst(le));

            len += strlen(ar) + 4;
            for (; *ar; ar++)
            {
                if (*ar == '\\')
                    len++;
            }
        }
        args = (char *) palloc(len + 1);
        args[0] = '\0';
        foreach(le, stmt->args)
        {
            char       *s = strVal(lfirst(le));
            char       *d = args + strlen(args);

            while (*s)
            {
                if (*s == '\\')
                    *d++ = '\\';
                *d++ = *s++;
            }
            strcpy(d, "\\000");
        }
        values[Anum_pg_trigger_tgnargs - 1] = Int16GetDatum(nargs);
        values[Anum_pg_trigger_tgargs - 1] = DirectFunctionCall1(byteain,
                                                      CStringGetDatum(args));
    }
    else
    {
        values[Anum_pg_trigger_tgnargs - 1] = Int16GetDatum(0);
        values[Anum_pg_trigger_tgargs - 1] = DirectFunctionCall1(byteain,
                                                        CStringGetDatum(""));
    }

    /* build column number array if it's a column-specific trigger */
    ncolumns = list_length(stmt->columns);
    if (ncolumns == 0)
        columns = NULL;
    else
    {
        ListCell   *cell;
        int         i = 0;

        columns = (int16 *) palloc(ncolumns * sizeof(int16));
        foreach(cell, stmt->columns)
        {
            char       *name = strVal(lfirst(cell));
            int16       attnum;
            int         j;

            /* Lookup column name.  System columns are not allowed */
            attnum = attnameAttNum(rel, name, false);
            if (attnum == InvalidAttrNumber)
                ereport(ERROR,
                        (errcode(ERRCODE_UNDEFINED_COLUMN),
                    errmsg("column \"%s\" of relation \"%s\" does not exist",
                           name, RelationGetRelationName(rel))));

            /* Check for duplicates */
            for (j = i - 1; j >= 0; j--)
            {
                if (columns[j] == attnum)
                    ereport(ERROR,
                            (errcode(ERRCODE_DUPLICATE_COLUMN),
                             errmsg("column \"%s\" specified more than once",
                                    name)));
            }

            columns[i++] = attnum;
        }
    }
    tgattr = buildint2vector(columns, ncolumns);
    values[Anum_pg_trigger_tgattr - 1] = PointerGetDatum(tgattr);

    /* set tgqual if trigger has WHEN clause */
    if (qual)
        values[Anum_pg_trigger_tgqual - 1] = CStringGetTextDatum(qual);
    else
        nulls[Anum_pg_trigger_tgqual - 1] = true;

    tuple = heap_form_tuple(tgrel->rd_att, values, nulls);

    /* force tuple to have the desired OID */
    HeapTupleSetOid(tuple, trigoid);

    /*
     * Insert tuple into pg_trigger.
     */
    simple_heap_insert(tgrel, tuple);

    CatalogUpdateIndexes(tgrel, tuple);

    heap_freetuple(tuple);
    heap_close(tgrel, RowExclusiveLock);

    pfree(DatumGetPointer(values[Anum_pg_trigger_tgname - 1]));
    pfree(DatumGetPointer(values[Anum_pg_trigger_tgargs - 1]));
    pfree(DatumGetPointer(values[Anum_pg_trigger_tgattr - 1]));

    /*
     * Update relation's pg_class entry.  Crucial side-effect: other backends
     * (and this one too!) are sent SI message to make them rebuild relcache
     * entries.
     */
    pgrel = heap_open(RelationRelationId, RowExclusiveLock);
    tuple = SearchSysCacheCopy1(RELOID,
                                ObjectIdGetDatum(RelationGetRelid(rel)));
    if (!HeapTupleIsValid(tuple))
        elog(ERROR, "cache lookup failed for relation %u",
             RelationGetRelid(rel));

    ((Form_pg_class) GETSTRUCT(tuple))->relhastriggers = true;

    simple_heap_update(pgrel, &tuple->t_self, tuple);

    CatalogUpdateIndexes(pgrel, tuple);

    heap_freetuple(tuple);
    heap_close(pgrel, RowExclusiveLock);

    /*
     * We used to try to update the rel's relcache entry here, but that's
     * fairly pointless since it will happen as a byproduct of the upcoming
     * CommandCounterIncrement...
     */

    /*
     * Record dependencies for trigger.  Always place a normal dependency on
     * the function.
     */
    myself.classId = TriggerRelationId;
    myself.objectId = trigoid;
    myself.objectSubId = 0;

    referenced.classId = ProcedureRelationId;
    referenced.objectId = funcoid;
    referenced.objectSubId = 0;
    recordDependencyOn(&myself, &referenced, DEPENDENCY_NORMAL);

    if (isInternal && OidIsValid(constraintOid))
    {
        /*
         * Internally-generated trigger for a constraint, so make it an
         * internal dependency of the constraint.  We can skip depending on
         * the relation(s), as there'll be an indirect dependency via the
         * constraint.
         */
        referenced.classId = ConstraintRelationId;
        referenced.objectId = constraintOid;
        referenced.objectSubId = 0;
        recordDependencyOn(&myself, &referenced, DEPENDENCY_INTERNAL);
    }
    else
    {
        /*
         * User CREATE TRIGGER, so place dependencies.  We make trigger be
         * auto-dropped if its relation is dropped or if the FK relation is
         * dropped.  (Auto drop is compatible with our pre-7.3 behavior.)
         */
        referenced.classId = RelationRelationId;
        referenced.objectId = RelationGetRelid(rel);
        referenced.objectSubId = 0;
        recordDependencyOn(&myself, &referenced, DEPENDENCY_AUTO);
        if (OidIsValid(constrrelid))
        {
            referenced.classId = RelationRelationId;
            referenced.objectId = constrrelid;
            referenced.objectSubId = 0;
            recordDependencyOn(&myself, &referenced, DEPENDENCY_AUTO);
        }
        /* Not possible to have an index dependency in this case */
        Assert(!OidIsValid(indexOid));

        /*
         * If it's a user-specified constraint trigger, make the constraint
         * internally dependent on the trigger instead of vice versa.
         */
        if (OidIsValid(constraintOid))
        {
            referenced.classId = ConstraintRelationId;
            referenced.objectId = constraintOid;
            referenced.objectSubId = 0;
            recordDependencyOn(&referenced, &myself, DEPENDENCY_INTERNAL);
        }
    }

    /* If column-specific trigger, add normal dependencies on columns */
    if (columns != NULL)
    {
        int         i;

        referenced.classId = RelationRelationId;
        referenced.objectId = RelationGetRelid(rel);
        for (i = 0; i < ncolumns; i++)
        {
            referenced.objectSubId = columns[i];
            recordDependencyOn(&myself, &referenced, DEPENDENCY_NORMAL);
        }
    }

    /*
     * If it has a WHEN clause, add dependencies on objects mentioned in the
     * expression (eg, functions, as well as any columns used).
     */
    if (whenClause != NULL)
        recordDependencyOnExpr(&myself, whenClause, whenRtable,
                               DEPENDENCY_NORMAL);

    /* Post creation hook for new trigger */
    InvokeObjectPostCreateHookArg(TriggerRelationId, trigoid, 0,
                                  isInternal);

    /* Keep lock on target rel until end of xact */
    heap_close(rel, NoLock);

    return myself;
}


/*
 * Convert legacy (pre-7.3) CREATE CONSTRAINT TRIGGER commands into
 * full-fledged foreign key constraints.
 *
 * The conversion is complex because a pre-7.3 foreign key involved three
 * separate triggers, which were reported separately in dumps.  While the
 * single trigger on the referencing table adds no new information, we need
 * to know the trigger functions of both of the triggers on the referenced
 * table to build the constraint declaration.  Also, due to lack of proper
 * dependency checking pre-7.3, it is possible that the source database had
 * an incomplete set of triggers resulting in an only partially enforced
 * FK constraint.  (This would happen if one of the tables had been dropped
 * and re-created, but only if the DB had been affected by a 7.0 pg_dump bug
 * that caused loss of tgconstrrelid information.)  We choose to translate to
 * an FK constraint only when we've seen all three triggers of a set.  This is
 * implemented by storing unmatched items in a list in TopMemoryContext.
 * We match triggers together by comparing the trigger arguments (which
 * include constraint name, table and column names, so should be good enough).
 */
typedef struct
{
    List       *args;           /* list of (T_String) Values or NIL */
    Oid         funcoids[3];    /* OIDs of trigger functions */
    /* The three function OIDs are stored in the order update, delete, child */
} OldTriggerInfo;

static void
ConvertTriggerToFK(CreateTrigStmt *stmt, Oid funcoid)
{
    static List *info_list = NIL;

    static const char *const funcdescr[3] = {
        gettext_noop("Found referenced table's UPDATE trigger."),
        gettext_noop("Found referenced table's DELETE trigger."),
        gettext_noop("Found referencing table's trigger.")
    };

    char       *constr_name;
    char       *fk_table_name;
    char       *pk_table_name;
    char        fk_matchtype = FKCONSTR_MATCH_SIMPLE;
    List       *fk_attrs = NIL;
    List       *pk_attrs = NIL;
    StringInfoData buf;
    int         funcnum;
    OldTriggerInfo *info = NULL;
    ListCell   *l;
    int         i;

    /* Parse out the trigger arguments */
    constr_name = strVal(linitial(stmt->args));
    fk_table_name = strVal(lsecond(stmt->args));
    pk_table_name = strVal(lthird(stmt->args));
    i = 0;
    foreach(l, stmt->args)
    {
        Value      *arg = (Value *) lfirst(l);

        i++;
        if (i < 4)              /* skip constraint and table names */
            continue;
        if (i == 4)             /* handle match type */
        {
            if (strcmp(strVal(arg), "FULL") == 0)
                fk_matchtype = FKCONSTR_MATCH_FULL;
            else
                fk_matchtype = FKCONSTR_MATCH_SIMPLE;
            continue;
        }
        if (i % 2)
            fk_attrs = lappend(fk_attrs, arg);
        else
            pk_attrs = lappend(pk_attrs, arg);
    }

    /* Prepare description of constraint for use in messages */
    initStringInfo(&buf);
    appendStringInfo(&buf, "FOREIGN KEY %s(",
                     quote_identifier(fk_table_name));
    i = 0;
    foreach(l, fk_attrs)
    {
        Value      *arg = (Value *) lfirst(l);

        if (i++ > 0)
            appendStringInfoChar(&buf, ',');
        appendStringInfoString(&buf, quote_identifier(strVal(arg)));
    }
    appendStringInfo(&buf, ") REFERENCES %s(",
                     quote_identifier(pk_table_name));
    i = 0;
    foreach(l, pk_attrs)
    {
        Value      *arg = (Value *) lfirst(l);

        if (i++ > 0)
            appendStringInfoChar(&buf, ',');
        appendStringInfoString(&buf, quote_identifier(strVal(arg)));
    }
    appendStringInfoChar(&buf, ')');

    /* Identify class of trigger --- update, delete, or referencing-table */
    switch (funcoid)
    {
        case F_RI_FKEY_CASCADE_UPD:
        case F_RI_FKEY_RESTRICT_UPD:
        case F_RI_FKEY_SETNULL_UPD:
        case F_RI_FKEY_SETDEFAULT_UPD:
        case F_RI_FKEY_NOACTION_UPD:
            funcnum = 0;
            break;

        case F_RI_FKEY_CASCADE_DEL:
        case F_RI_FKEY_RESTRICT_DEL:
        case F_RI_FKEY_SETNULL_DEL:
        case F_RI_FKEY_SETDEFAULT_DEL:
        case F_RI_FKEY_NOACTION_DEL:
            funcnum = 1;
            break;

        default:
            funcnum = 2;
            break;
    }

    /* See if we have a match to this trigger */
    foreach(l, info_list)
    {
        info = (OldTriggerInfo *) lfirst(l);
        if (info->funcoids[funcnum] == InvalidOid &&
            equal(info->args, stmt->args))
        {
            info->funcoids[funcnum] = funcoid;
            break;
        }
    }

    if (l == NULL)
    {
        /* First trigger of set, so create a new list entry */
        MemoryContext oldContext;

        ereport(NOTICE,
        (errmsg("ignoring incomplete trigger group for constraint \"%s\" %s",
                constr_name, buf.data),
         errdetail_internal("%s", _(funcdescr[funcnum]))));
        oldContext = MemoryContextSwitchTo(TopMemoryContext);
        info = (OldTriggerInfo *) palloc0(sizeof(OldTriggerInfo));
        info->args = copyObject(stmt->args);
        info->funcoids[funcnum] = funcoid;
        info_list = lappend(info_list, info);
        MemoryContextSwitchTo(oldContext);
    }
    else if (info->funcoids[0] == InvalidOid ||
             info->funcoids[1] == InvalidOid ||
             info->funcoids[2] == InvalidOid)
    {
        /* Second trigger of set */
        ereport(NOTICE,
        (errmsg("ignoring incomplete trigger group for constraint \"%s\" %s",
                constr_name, buf.data),
         errdetail_internal("%s", _(funcdescr[funcnum]))));
    }
    else
    {
        /* OK, we have a set, so make the FK constraint ALTER TABLE cmd */
        AlterTableStmt *atstmt = makeNode(AlterTableStmt);
        AlterTableCmd *atcmd = makeNode(AlterTableCmd);
        Constraint *fkcon = makeNode(Constraint);

        ereport(NOTICE,
                (errmsg("converting trigger group into constraint \"%s\" %s",
                        constr_name, buf.data),
                 errdetail_internal("%s", _(funcdescr[funcnum]))));
        fkcon->contype = CONSTR_FOREIGN;
        fkcon->location = -1;
        if (funcnum == 2)
        {
            /* This trigger is on the FK table */
            atstmt->relation = stmt->relation;
            if (stmt->constrrel)
                fkcon->pktable = stmt->constrrel;
            else
            {
                /* Work around ancient pg_dump bug that omitted constrrel */
                fkcon->pktable = makeRangeVar(NULL, pk_table_name, -1);
            }
        }
        else
        {
            /* This trigger is on the PK table */
            fkcon->pktable = stmt->relation;
            if (stmt->constrrel)
                atstmt->relation = stmt->constrrel;
            else
            {
                /* Work around ancient pg_dump bug that omitted constrrel */
                atstmt->relation = makeRangeVar(NULL, fk_table_name, -1);
            }
        }
        atstmt->cmds = list_make1(atcmd);
        atstmt->relkind = OBJECT_TABLE;
        atcmd->subtype = AT_AddConstraint;
        atcmd->def = (Node *) fkcon;
        if (strcmp(constr_name, "<unnamed>") == 0)
            fkcon->conname = NULL;
        else
            fkcon->conname = constr_name;
        fkcon->fk_attrs = fk_attrs;
        fkcon->pk_attrs = pk_attrs;
        fkcon->fk_matchtype = fk_matchtype;
        switch (info->funcoids[0])
        {
            case F_RI_FKEY_NOACTION_UPD:
                fkcon->fk_upd_action = FKCONSTR_ACTION_NOACTION;
                break;
            case F_RI_FKEY_CASCADE_UPD:
                fkcon->fk_upd_action = FKCONSTR_ACTION_CASCADE;
                break;
            case F_RI_FKEY_RESTRICT_UPD:
                fkcon->fk_upd_action = FKCONSTR_ACTION_RESTRICT;
                break;
            case F_RI_FKEY_SETNULL_UPD:
                fkcon->fk_upd_action = FKCONSTR_ACTION_SETNULL;
                break;
            case F_RI_FKEY_SETDEFAULT_UPD:
                fkcon->fk_upd_action = FKCONSTR_ACTION_SETDEFAULT;
                break;
            default:
                /* can't get here because of earlier checks */
                elog(ERROR, "confused about RI update function");
        }
        switch (info->funcoids[1])
        {
            case F_RI_FKEY_NOACTION_DEL:
                fkcon->fk_del_action = FKCONSTR_ACTION_NOACTION;
                break;
            case F_RI_FKEY_CASCADE_DEL:
                fkcon->fk_del_action = FKCONSTR_ACTION_CASCADE;
                break;
            case F_RI_FKEY_RESTRICT_DEL:
                fkcon->fk_del_action = FKCONSTR_ACTION_RESTRICT;
                break;
            case F_RI_FKEY_SETNULL_DEL:
                fkcon->fk_del_action = FKCONSTR_ACTION_SETNULL;
                break;
            case F_RI_FKEY_SETDEFAULT_DEL:
                fkcon->fk_del_action = FKCONSTR_ACTION_SETDEFAULT;
                break;
            default:
                /* can't get here because of earlier checks */
                elog(ERROR, "confused about RI delete function");
        }
        fkcon->deferrable = stmt->deferrable;
        fkcon->initdeferred = stmt->initdeferred;
        fkcon->skip_validation = false;
        fkcon->initially_valid = true;

        /* ... and execute it */
        ProcessUtility((Node *) atstmt,
                       "(generated ALTER TABLE ADD FOREIGN KEY command)",
                       PROCESS_UTILITY_SUBCOMMAND, NULL,
                       None_Receiver, NULL);

        /* Remove the matched item from the list */
        info_list = list_delete_ptr(info_list, info);
        pfree(info);
        /* We leak the copied args ... not worth worrying about */
    }
}

/*
 * Guts of trigger deletion.
 */
void
RemoveTriggerById(Oid trigOid)
{
    Relation    tgrel;
    SysScanDesc tgscan;
    ScanKeyData skey[1];
    HeapTuple   tup;
    Oid         relid;
    Relation    rel;

    tgrel = heap_open(TriggerRelationId, RowExclusiveLock);

    /*
     * Find the trigger to delete.
     */
    ScanKeyInit(&skey[0],
                ObjectIdAttributeNumber,
                BTEqualStrategyNumber, F_OIDEQ,
                ObjectIdGetDatum(trigOid));

    tgscan = systable_beginscan(tgrel, TriggerOidIndexId, true,
                                NULL, 1, skey);

    tup = systable_getnext(tgscan);
    if (!HeapTupleIsValid(tup))
        elog(ERROR, "could not find tuple for trigger %u", trigOid);

    /*
     * Open and exclusive-lock the relation the trigger belongs to.
     */
    relid = ((Form_pg_trigger) GETSTRUCT(tup))->tgrelid;

    rel = heap_open(relid, AccessExclusiveLock);

    if (rel->rd_rel->relkind != RELKIND_RELATION &&
        rel->rd_rel->relkind != RELKIND_VIEW &&
        rel->rd_rel->relkind != RELKIND_FOREIGN_TABLE)
        ereport(ERROR,
                (errcode(ERRCODE_WRONG_OBJECT_TYPE),
                 errmsg("\"%s\" is not a table, view, or foreign table",
                        RelationGetRelationName(rel))));

    if (!allowSystemTableMods && IsSystemRelation(rel))
        ereport(ERROR,
                (errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
                 errmsg("permission denied: \"%s\" is a system catalog",
                        RelationGetRelationName(rel))));

    /*
     * Delete the pg_trigger tuple.
     */
    simple_heap_delete(tgrel, &tup->t_self);

    systable_endscan(tgscan);
    heap_close(tgrel, RowExclusiveLock);

    /*
     * We do not bother to try to determine whether any other triggers remain,
     * which would be needed in order to decide whether it's safe to clear the
     * relation's relhastriggers.  (In any case, there might be a concurrent
     * process adding new triggers.)  Instead, just force a relcache inval to
     * make other backends (and this one too!) rebuild their relcache entries.
     * There's no great harm in leaving relhastriggers true even if there are
     * no triggers left.
     */
    CacheInvalidateRelcache(rel);

    /* Keep lock on trigger's rel until end of xact */
    heap_close(rel, NoLock);
}

/*
 * get_trigger_oid - Look up a trigger by name to find its OID.
 *
 * If missing_ok is false, throw an error if trigger not found.  If
 * true, just return InvalidOid.
 */
Oid
get_trigger_oid(Oid relid, const char *trigname, bool missing_ok)
{
    Relation    tgrel;
    ScanKeyData skey[2];
    SysScanDesc tgscan;
    HeapTuple   tup;
    Oid         oid;

    /*
     * Find the trigger, verify permissions, set up object address
     */
    tgrel = heap_open(TriggerRelationId, AccessShareLock);

    ScanKeyInit(&skey[0],
                Anum_pg_trigger_tgrelid,
                BTEqualStrategyNumber, F_OIDEQ,
                ObjectIdGetDatum(relid));
    ScanKeyInit(&skey[1],
                Anum_pg_trigger_tgname,
                BTEqualStrategyNumber, F_NAMEEQ,
                CStringGetDatum(trigname));

    tgscan = systable_beginscan(tgrel, TriggerRelidNameIndexId, true,
                                NULL, 2, skey);

    tup = systable_getnext(tgscan);

    if (!HeapTupleIsValid(tup))
    {
        if (!missing_ok)
            ereport(ERROR,
                    (errcode(ERRCODE_UNDEFINED_OBJECT),
                     errmsg("trigger \"%s\" for table \"%s\" does not exist",
                            trigname, get_rel_name(relid))));
        oid = InvalidOid;
    }
    else
    {
        oid = HeapTupleGetOid(tup);
    }

    systable_endscan(tgscan);
    heap_close(tgrel, AccessShareLock);
    return oid;
}

/*
 * Perform permissions and integrity checks before acquiring a relation lock.
 */
static void
RangeVarCallbackForRenameTrigger(const RangeVar *rv, Oid relid, Oid oldrelid,
                                 void *arg)
{
    HeapTuple   tuple;
    Form_pg_class form;

    tuple = SearchSysCache1(RELOID, ObjectIdGetDatum(relid));
    if (!HeapTupleIsValid(tuple))
        return;                 /* concurrently dropped */
    form = (Form_pg_class) GETSTRUCT(tuple);

    /* only tables and views can have triggers */
    if (form->relkind != RELKIND_RELATION && form->relkind != RELKIND_VIEW &&
        form->relkind != RELKIND_FOREIGN_TABLE)
        ereport(ERROR,
                (errcode(ERRCODE_WRONG_OBJECT_TYPE),
                 errmsg("\"%s\" is not a table, view, or foreign table",
                        rv->relname)));

    /* you must own the table to rename one of its triggers */
    if (!pg_class_ownercheck(relid, GetUserId()))
        aclcheck_error(ACLCHECK_NOT_OWNER, ACL_KIND_CLASS, rv->relname);
    if (!allowSystemTableMods && IsSystemClass(relid, form))
        ereport(ERROR,
                (errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
                 errmsg("permission denied: \"%s\" is a system catalog",
                        rv->relname)));

    ReleaseSysCache(tuple);
}

/*
 *      renametrig      - changes the name of a trigger on a relation
 *
 *      trigger name is changed in trigger catalog.
 *      No record of the previous name is kept.
 *
 *      get proper relrelation from relation catalog (if not arg)
 *      scan trigger catalog
 *              for name conflict (within rel)
 *              for original trigger (if not arg)
 *      modify tgname in trigger tuple
 *      update row in catalog
 */
ObjectAddress
renametrig(RenameStmt *stmt)
{
    Oid         tgoid;
    Relation    targetrel;
    Relation    tgrel;
    HeapTuple   tuple;
    SysScanDesc tgscan;
    ScanKeyData key[2];
    Oid         relid;
    ObjectAddress address;

    /*
     * Look up name, check permissions, and acquire lock (which we will NOT
     * release until end of transaction).
     */
    relid = RangeVarGetRelidExtended(stmt->relation, AccessExclusiveLock,
                                     false, false,
                                     RangeVarCallbackForRenameTrigger,
                                     NULL);

    /* Have lock already, so just need to build relcache entry. */
    targetrel = relation_open(relid, NoLock);

    /*
     * Scan pg_trigger twice for existing triggers on relation.  We do this in
     * order to ensure a trigger does not exist with newname (The unique index
     * on tgrelid/tgname would complain anyway) and to ensure a trigger does
     * exist with oldname.
     *
     * NOTE that this is cool only because we have AccessExclusiveLock on the
     * relation, so the trigger set won't be changing underneath us.
     */
    tgrel = heap_open(TriggerRelationId, RowExclusiveLock);

    /*
     * First pass -- look for name conflict
     */
    ScanKeyInit(&key[0],
                Anum_pg_trigger_tgrelid,
                BTEqualStrategyNumber, F_OIDEQ,
                ObjectIdGetDatum(relid));
    ScanKeyInit(&key[1],
                Anum_pg_trigger_tgname,
                BTEqualStrategyNumber, F_NAMEEQ,
                PointerGetDatum(stmt->newname));
    tgscan = systable_beginscan(tgrel, TriggerRelidNameIndexId, true,
                                NULL, 2, key);
    if (HeapTupleIsValid(tuple = systable_getnext(tgscan)))
        ereport(ERROR,
                (errcode(ERRCODE_DUPLICATE_OBJECT),
                 errmsg("trigger \"%s\" for relation \"%s\" already exists",
                        stmt->newname, RelationGetRelationName(targetrel))));
    systable_endscan(tgscan);

    /*
     * Second pass -- look for trigger existing with oldname and update
     */
    ScanKeyInit(&key[0],
                Anum_pg_trigger_tgrelid,
                BTEqualStrategyNumber, F_OIDEQ,
                ObjectIdGetDatum(relid));
    ScanKeyInit(&key[1],
                Anum_pg_trigger_tgname,
                BTEqualStrategyNumber, F_NAMEEQ,
                PointerGetDatum(stmt->subname));
    tgscan = systable_beginscan(tgrel, TriggerRelidNameIndexId, true,
                                NULL, 2, key);
    if (HeapTupleIsValid(tuple = systable_getnext(tgscan)))
    {
        tgoid = HeapTupleGetOid(tuple);

        /*
         * Update pg_trigger tuple with new tgname.
         */
        tuple = heap_copytuple(tuple);  /* need a modifiable copy */

        namestrcpy(&((Form_pg_trigger) GETSTRUCT(tuple))->tgname,
                   stmt->newname);

        simple_heap_update(tgrel, &tuple->t_self, tuple);

        /* keep system catalog indexes current */
        CatalogUpdateIndexes(tgrel, tuple);

        InvokeObjectPostAlterHook(TriggerRelationId,
                                  HeapTupleGetOid(tuple), 0);

        /*
         * Invalidate relation's relcache entry so that other backends (and
         * this one too!) are sent SI message to make them rebuild relcache
         * entries.  (Ideally this should happen automatically...)
         */
        CacheInvalidateRelcache(targetrel);
    }
    else
    {
        ereport(ERROR,
                (errcode(ERRCODE_UNDEFINED_OBJECT),
                 errmsg("trigger \"%s\" for table \"%s\" does not exist",
                        stmt->subname, RelationGetRelationName(targetrel))));
    }

    ObjectAddressSet(address, TriggerRelationId, tgoid);

    systable_endscan(tgscan);

    heap_close(tgrel, RowExclusiveLock);

    /*
     * Close rel, but keep exclusive lock!
     */
    relation_close(targetrel, NoLock);

    return address;
}


/*
 * EnableDisableTrigger()
 *
 *  Called by ALTER TABLE ENABLE/DISABLE [ REPLICA | ALWAYS ] TRIGGER
 *  to change 'tgenabled' field for the specified trigger(s)
 *
 * rel: relation to process (caller must hold suitable lock on it)
 * tgname: trigger to process, or NULL to scan all triggers
 * fires_when: new value for tgenabled field. In addition to generic
 *             enablement/disablement, this also defines when the trigger
 *             should be fired in session replication roles.
 * skip_system: if true, skip "system" triggers (constraint triggers)
 *
 * Caller should have checked permissions for the table; here we also
 * enforce that superuser privilege is required to alter the state of
 * system triggers
 */
void
EnableDisableTrigger(Relation rel, const char *tgname,
                     char fires_when, bool skip_system)
{
    Relation    tgrel;
    int         nkeys;
    ScanKeyData keys[2];
    SysScanDesc tgscan;
    HeapTuple   tuple;
    bool        found;
    bool        changed;

    /* Scan the relevant entries in pg_triggers */
    tgrel = heap_open(TriggerRelationId, RowExclusiveLock);

    ScanKeyInit(&keys[0],
                Anum_pg_trigger_tgrelid,
                BTEqualStrategyNumber, F_OIDEQ,
                ObjectIdGetDatum(RelationGetRelid(rel)));
    if (tgname)
    {
        ScanKeyInit(&keys[1],
                    Anum_pg_trigger_tgname,
                    BTEqualStrategyNumber, F_NAMEEQ,
                    CStringGetDatum(tgname));
        nkeys = 2;
    }
    else
        nkeys = 1;

    tgscan = systable_beginscan(tgrel, TriggerRelidNameIndexId, true,
                                NULL, nkeys, keys);

    found = changed = false;

    while (HeapTupleIsValid(tuple = systable_getnext(tgscan)))
    {
        Form_pg_trigger oldtrig = (Form_pg_trigger) GETSTRUCT(tuple);

        if (oldtrig->tgisinternal)
        {
            /* system trigger ... ok to process? */
            if (skip_system)
                continue;
            if (!superuser())
                ereport(ERROR,
                        (errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
                      errmsg("permission denied: \"%s\" is a system trigger",
                             NameStr(oldtrig->tgname))));
        }

        found = true;

        if (oldtrig->tgenabled != fires_when)
        {
            /* need to change this one ... make a copy to scribble on */
            HeapTuple   newtup = heap_copytuple(tuple);
            Form_pg_trigger newtrig = (Form_pg_trigger) GETSTRUCT(newtup);

            newtrig->tgenabled = fires_when;

            simple_heap_update(tgrel, &newtup->t_self, newtup);

            /* Keep catalog indexes current */
            CatalogUpdateIndexes(tgrel, newtup);

            heap_freetuple(newtup);

            changed = true;
        }

        InvokeObjectPostAlterHook(TriggerRelationId,
                                  HeapTupleGetOid(tuple), 0);
    }

    systable_endscan(tgscan);

    heap_close(tgrel, RowExclusiveLock);

    if (tgname && !found)
        ereport(ERROR,
                (errcode(ERRCODE_UNDEFINED_OBJECT),
                 errmsg("trigger \"%s\" for table \"%s\" does not exist",
                        tgname, RelationGetRelationName(rel))));

    /*
     * If we changed anything, broadcast a SI inval message to force each
     * backend (including our own!) to rebuild relation's relcache entry.
     * Otherwise they will fail to apply the change promptly.
     */
    if (changed)
        CacheInvalidateRelcache(rel);
}


/*
 * Build trigger data to attach to the given relcache entry.
 *
 * Note that trigger data attached to a relcache entry must be stored in
 * CacheMemoryContext to ensure it survives as long as the relcache entry.
 * But we should be running in a less long-lived working context.  To avoid
 * leaking cache memory if this routine fails partway through, we build a
 * temporary TriggerDesc in working memory and then copy the completed
 * structure into cache memory.
 */
void
RelationBuildTriggers(Relation relation)
{
    TriggerDesc *trigdesc;
    int         numtrigs;
    int         maxtrigs;
    Trigger    *triggers;
    Relation    tgrel;
    ScanKeyData skey;
    SysScanDesc tgscan;
    HeapTuple   htup;
    MemoryContext oldContext;
    int         i;

    /*
     * Allocate a working array to hold the triggers (the array is extended if
     * necessary)
     */
    maxtrigs = 16;
    triggers = (Trigger *) palloc(maxtrigs * sizeof(Trigger));
    numtrigs = 0;

    /*
     * Note: since we scan the triggers using TriggerRelidNameIndexId, we will
     * be reading the triggers in name order, except possibly during
     * emergency-recovery operations (ie, IgnoreSystemIndexes). This in turn
     * ensures that triggers will be fired in name order.
     */
    ScanKeyInit(&skey,
                Anum_pg_trigger_tgrelid,
                BTEqualStrategyNumber, F_OIDEQ,
                ObjectIdGetDatum(RelationGetRelid(relation)));

    tgrel = heap_open(TriggerRelationId, AccessShareLock);
    tgscan = systable_beginscan(tgrel, TriggerRelidNameIndexId, true,
                                NULL, 1, &skey);

    while (HeapTupleIsValid(htup = systable_getnext(tgscan)))
    {
        Form_pg_trigger pg_trigger = (Form_pg_trigger) GETSTRUCT(htup);
        Trigger    *build;
        Datum       datum;
        bool        isnull;

        if (numtrigs >= maxtrigs)
        {
            maxtrigs *= 2;
            triggers = (Trigger *) repalloc(triggers, maxtrigs * sizeof(Trigger));
        }
        build = &(triggers[numtrigs]);

        build->tgoid = HeapTupleGetOid(htup);
        build->tgname = DatumGetCString(DirectFunctionCall1(nameout,
                                         NameGetDatum(&pg_trigger->tgname)));
        build->tgfoid = pg_trigger->tgfoid;
        build->tgtype = pg_trigger->tgtype;
        build->tgenabled = pg_trigger->tgenabled;
        build->tgisinternal = pg_trigger->tgisinternal;
        build->tgconstrrelid = pg_trigger->tgconstrrelid;
        build->tgconstrindid = pg_trigger->tgconstrindid;
        build->tgconstraint = pg_trigger->tgconstraint;
        build->tgdeferrable = pg_trigger->tgdeferrable;
        build->tginitdeferred = pg_trigger->tginitdeferred;
        build->tgnargs = pg_trigger->tgnargs;
        /* tgattr is first var-width field, so OK to access directly */
        build->tgnattr = pg_trigger->tgattr.dim1;
        if (build->tgnattr > 0)
        {
            build->tgattr = (int16 *) palloc(build->tgnattr * sizeof(int16));
            memcpy(build->tgattr, &(pg_trigger->tgattr.values),
                   build->tgnattr * sizeof(int16));
        }
        else
            build->tgattr = NULL;
        if (build->tgnargs > 0)
        {
            bytea      *val;
            char       *p;

            val = DatumGetByteaP(fastgetattr(htup,
                                             Anum_pg_trigger_tgargs,
                                             tgrel->rd_att, &isnull));
            if (isnull)
                elog(ERROR, "tgargs is null in trigger for relation \"%s\"",
                     RelationGetRelationName(relation));
            p = (char *) VARDATA(val);
            build->tgargs = (char **) palloc(build->tgnargs * sizeof(char *));
            for (i = 0; i < build->tgnargs; i++)
            {
                build->tgargs[i] = pstrdup(p);
                p += strlen(p) + 1;
            }
        }
        else
            build->tgargs = NULL;
        datum = fastgetattr(htup, Anum_pg_trigger_tgqual,
                            tgrel->rd_att, &isnull);
        if (!isnull)
            build->tgqual = TextDatumGetCString(datum);
        else
            build->tgqual = NULL;

        numtrigs++;
    }

    systable_endscan(tgscan);
    heap_close(tgrel, AccessShareLock);

    /* There might not be any triggers */
    if (numtrigs == 0)
    {
        pfree(triggers);
        return;
    }

    /* Build trigdesc */
    trigdesc = (TriggerDesc *) palloc0(sizeof(TriggerDesc));
    trigdesc->triggers = triggers;
    trigdesc->numtriggers = numtrigs;
    for (i = 0; i < numtrigs; i++)
        SetTriggerFlags(trigdesc, &(triggers[i]));

    /* Copy completed trigdesc into cache storage */
    oldContext = MemoryContextSwitchTo(CacheMemoryContext);
    relation->trigdesc = CopyTriggerDesc(trigdesc);
    MemoryContextSwitchTo(oldContext);

    /* Release working memory */
    FreeTriggerDesc(trigdesc);
}

/*
 * Update the TriggerDesc's hint flags to include the specified trigger
 */
static void
SetTriggerFlags(TriggerDesc *trigdesc, Trigger *trigger)
{
    int16       tgtype = trigger->tgtype;

    trigdesc->trig_insert_before_row |=
        TRIGGER_TYPE_MATCHES(tgtype, TRIGGER_TYPE_ROW,
                             TRIGGER_TYPE_BEFORE, TRIGGER_TYPE_INSERT);
    trigdesc->trig_insert_after_row |=
        TRIGGER_TYPE_MATCHES(tgtype, TRIGGER_TYPE_ROW,
                             TRIGGER_TYPE_AFTER, TRIGGER_TYPE_INSERT);
    trigdesc->trig_insert_instead_row |=
        TRIGGER_TYPE_MATCHES(tgtype, TRIGGER_TYPE_ROW,
                             TRIGGER_TYPE_INSTEAD, TRIGGER_TYPE_INSERT);
    trigdesc->trig_insert_before_statement |=
        TRIGGER_TYPE_MATCHES(tgtype, TRIGGER_TYPE_STATEMENT,
                             TRIGGER_TYPE_BEFORE, TRIGGER_TYPE_INSERT);
    trigdesc->trig_insert_after_statement |=
        TRIGGER_TYPE_MATCHES(tgtype, TRIGGER_TYPE_STATEMENT,
                             TRIGGER_TYPE_AFTER, TRIGGER_TYPE_INSERT);
    trigdesc->trig_update_before_row |=
        TRIGGER_TYPE_MATCHES(tgtype, TRIGGER_TYPE_ROW,
                             TRIGGER_TYPE_BEFORE, TRIGGER_TYPE_UPDATE);
    trigdesc->trig_update_after_row |=
        TRIGGER_TYPE_MATCHES(tgtype, TRIGGER_TYPE_ROW,
                             TRIGGER_TYPE_AFTER, TRIGGER_TYPE_UPDATE);
    trigdesc->trig_update_instead_row |=
        TRIGGER_TYPE_MATCHES(tgtype, TRIGGER_TYPE_ROW,
                             TRIGGER_TYPE_INSTEAD, TRIGGER_TYPE_UPDATE);
    trigdesc->trig_update_before_statement |=
        TRIGGER_TYPE_MATCHES(tgtype, TRIGGER_TYPE_STATEMENT,
                             TRIGGER_TYPE_BEFORE, TRIGGER_TYPE_UPDATE);
    trigdesc->trig_update_after_statement |=
        TRIGGER_TYPE_MATCHES(tgtype, TRIGGER_TYPE_STATEMENT,
                             TRIGGER_TYPE_AFTER, TRIGGER_TYPE_UPDATE);
    trigdesc->trig_delete_before_row |=
        TRIGGER_TYPE_MATCHES(tgtype, TRIGGER_TYPE_ROW,
                             TRIGGER_TYPE_BEFORE, TRIGGER_TYPE_DELETE);
    trigdesc->trig_delete_after_row |=
        TRIGGER_TYPE_MATCHES(tgtype, TRIGGER_TYPE_ROW,
                             TRIGGER_TYPE_AFTER, TRIGGER_TYPE_DELETE);
    trigdesc->trig_delete_instead_row |=
        TRIGGER_TYPE_MATCHES(tgtype, TRIGGER_TYPE_ROW,
                             TRIGGER_TYPE_INSTEAD, TRIGGER_TYPE_DELETE);
    trigdesc->trig_delete_before_statement |=
        TRIGGER_TYPE_MATCHES(tgtype, TRIGGER_TYPE_STATEMENT,
                             TRIGGER_TYPE_BEFORE, TRIGGER_TYPE_DELETE);
    trigdesc->trig_delete_after_statement |=
        TRIGGER_TYPE_MATCHES(tgtype, TRIGGER_TYPE_STATEMENT,
                             TRIGGER_TYPE_AFTER, TRIGGER_TYPE_DELETE);
    /* there are no row-level truncate triggers */
    trigdesc->trig_truncate_before_statement |=
        TRIGGER_TYPE_MATCHES(tgtype, TRIGGER_TYPE_STATEMENT,
                             TRIGGER_TYPE_BEFORE, TRIGGER_TYPE_TRUNCATE);
    trigdesc->trig_truncate_after_statement |=
        TRIGGER_TYPE_MATCHES(tgtype, TRIGGER_TYPE_STATEMENT,
                             TRIGGER_TYPE_AFTER, TRIGGER_TYPE_TRUNCATE);
}

/*
 * Copy a TriggerDesc data structure.
 *
 * The copy is allocated in the current memory context.
 */
TriggerDesc *
CopyTriggerDesc(TriggerDesc *trigdesc)
{
    TriggerDesc *newdesc;
    Trigger    *trigger;
    int         i;

    if (trigdesc == NULL || trigdesc->numtriggers <= 0)
        return NULL;

    newdesc = (TriggerDesc *) palloc(sizeof(TriggerDesc));
    memcpy(newdesc, trigdesc, sizeof(TriggerDesc));

    trigger = (Trigger *) palloc(trigdesc->numtriggers * sizeof(Trigger));
    memcpy(trigger, trigdesc->triggers,
           trigdesc->numtriggers * sizeof(Trigger));
    newdesc->triggers = trigger;

    for (i = 0; i < trigdesc->numtriggers; i++)
    {
        trigger->tgname = pstrdup(trigger->tgname);
        if (trigger->tgnattr > 0)
        {
            int16      *newattr;

            newattr = (int16 *) palloc(trigger->tgnattr * sizeof(int16));
            memcpy(newattr, trigger->tgattr,
                   trigger->tgnattr * sizeof(int16));
            trigger->tgattr = newattr;
        }
        if (trigger->tgnargs > 0)
        {
            char      **newargs;
            int16       j;

            newargs = (char **) palloc(trigger->tgnargs * sizeof(char *));
            for (j = 0; j < trigger->tgnargs; j++)
                newargs[j] = pstrdup(trigger->tgargs[j]);
            trigger->tgargs = newargs;
        }
        if (trigger->tgqual)
            trigger->tgqual = pstrdup(trigger->tgqual);
        trigger++;
    }

    return newdesc;
}

/*
 * Free a TriggerDesc data structure.
 */
void
FreeTriggerDesc(TriggerDesc *trigdesc)
{
    Trigger    *trigger;
    int         i;

    if (trigdesc == NULL)
        return;

    trigger = trigdesc->triggers;
    for (i = 0; i < trigdesc->numtriggers; i++)
    {
        pfree(trigger->tgname);
        if (trigger->tgnattr > 0)
            pfree(trigger->tgattr);
        if (trigger->tgnargs > 0)
        {
            while (--(trigger->tgnargs) >= 0)
                pfree(trigger->tgargs[trigger->tgnargs]);
            pfree(trigger->tgargs);
        }
        if (trigger->tgqual)
            pfree(trigger->tgqual);
        trigger++;
    }
    pfree(trigdesc->triggers);
    pfree(trigdesc);
}

/*
 * Compare two TriggerDesc structures for logical equality.
 */
#ifdef NOT_USED
bool
equalTriggerDescs(TriggerDesc *trigdesc1, TriggerDesc *trigdesc2)
{
    int         i,
                j;

    /*
     * We need not examine the hint flags, just the trigger array itself; if
     * we have the same triggers with the same types, the flags should match.
     *
     * As of 7.3 we assume trigger set ordering is significant in the
     * comparison; so we just compare corresponding slots of the two sets.
     *
     * Note: comparing the stringToNode forms of the WHEN clauses means that
     * parse column locations will affect the result.  This is okay as long as
     * this function is only used for detecting exact equality, as for example
     * in checking for staleness of a cache entry.
     */
    if (trigdesc1 != NULL)
    {
        if (trigdesc2 == NULL)
            return false;
        if (trigdesc1->numtriggers != trigdesc2->numtriggers)
            return false;
        for (i = 0; i < trigdesc1->numtriggers; i++)
        {
            Trigger    *trig1 = trigdesc1->triggers + i;
            Trigger    *trig2 = trigdesc2->triggers + i;

            if (trig1->tgoid != trig2->tgoid)
                return false;
            if (strcmp(trig1->tgname, trig2->tgname) != 0)
                return false;
            if (trig1->tgfoid != trig2->tgfoid)
                return false;
            if (trig1->tgtype != trig2->tgtype)
                return false;
            if (trig1->tgenabled != trig2->tgenabled)
                return false;
            if (trig1->tgisinternal != trig2->tgisinternal)
                return false;
            if (trig1->tgconstrrelid != trig2->tgconstrrelid)
                return false;
            if (trig1->tgconstrindid != trig2->tgconstrindid)
                return false;
            if (trig1->tgconstraint != trig2->tgconstraint)
                return false;
            if (trig1->tgdeferrable != trig2->tgdeferrable)
                return false;
            if (trig1->tginitdeferred != trig2->tginitdeferred)
                return false;
            if (trig1->tgnargs != trig2->tgnargs)
                return false;
            if (trig1->tgnattr != trig2->tgnattr)
                return false;
            if (trig1->tgnattr > 0 &&
                memcmp(trig1->tgattr, trig2->tgattr,
                       trig1->tgnattr * sizeof(int16)) != 0)
                return false;
            for (j = 0; j < trig1->tgnargs; j++)
                if (strcmp(trig1->tgargs[j], trig2->tgargs[j]) != 0)
                    return false;
            if (trig1->tgqual == NULL && trig2->tgqual == NULL)
                 /* ok */ ;
            else if (trig1->tgqual == NULL || trig2->tgqual == NULL)
                return false;
            else if (strcmp(trig1->tgqual, trig2->tgqual) != 0)
                return false;
        }
    }
    else if (trigdesc2 != NULL)
        return false;
    return true;
}
#endif   /* NOT_USED */

/*
 * Call a trigger function.
 *
 *      trigdata: trigger descriptor.
 *      tgindx: trigger's index in finfo and instr arrays.
 *      finfo: array of cached trigger function call information.
 *      instr: optional array of EXPLAIN ANALYZE instrumentation state.
 *      per_tuple_context: memory context to execute the function in.
 *
 * Returns the tuple (or NULL) as returned by the function.
 */
static HeapTuple
ExecCallTriggerFunc(TriggerData *trigdata,
                    int tgindx,
                    FmgrInfo *finfo,
                    Instrumentation *instr,
                    MemoryContext per_tuple_context)
{
    FunctionCallInfoData fcinfo;
    PgStat_FunctionCallUsage fcusage;
    Datum       result;
    MemoryContext oldContext;

    finfo += tgindx;

    /*
     * We cache fmgr lookup info, to avoid making the lookup again on each
     * call.
     */
    if (finfo->fn_oid == InvalidOid)
        fmgr_info(trigdata->tg_trigger->tgfoid, finfo);

    Assert(finfo->fn_oid == trigdata->tg_trigger->tgfoid);

    /*
     * If doing EXPLAIN ANALYZE, start charging time to this trigger.
     */
    if (instr)
        InstrStartNode(instr + tgindx);

    /*
     * Do the function evaluation in the per-tuple memory context, so that
     * leaked memory will be reclaimed once per tuple. Note in particular that
     * any new tuple created by the trigger function will live till the end of
     * the tuple cycle.
     */
    oldContext = MemoryContextSwitchTo(per_tuple_context);

    /*
     * Call the function, passing no arguments but setting a context.
     */
    InitFunctionCallInfoData(fcinfo, finfo, 0,
                             InvalidOid, (Node *) trigdata, NULL);

    pgstat_init_function_usage(&fcinfo, &fcusage);

    MyTriggerDepth++;
    PG_TRY();
    {
        result = FunctionCallInvoke(&fcinfo);
    }
    PG_CATCH();
    {
        MyTriggerDepth--;
        PG_RE_THROW();
    }
    PG_END_TRY();
    MyTriggerDepth--;

    pgstat_end_function_usage(&fcusage, true);

    MemoryContextSwitchTo(oldContext);

    /*
     * Trigger protocol allows function to return a null pointer, but NOT to
     * set the isnull result flag.
     */
    if (fcinfo.isnull)
        ereport(ERROR,
                (errcode(ERRCODE_E_R_I_E_TRIGGER_PROTOCOL_VIOLATED),
                 errmsg("trigger function %u returned null value",
                        fcinfo.flinfo->fn_oid)));

    /*
     * If doing EXPLAIN ANALYZE, stop charging time to this trigger, and count
     * one "tuple returned" (really the number of firings).
     */
    if (instr)
        InstrStopNode(instr + tgindx, 1);

    return (HeapTuple) DatumGetPointer(result);
}

void
ExecBSInsertTriggers(EState *estate, ResultRelInfo *relinfo)
{
    TriggerDesc *trigdesc;
    int         i;
    TriggerData LocTriggerData;

    trigdesc = relinfo->ri_TrigDesc;

    if (trigdesc == NULL)
        return;
    if (!trigdesc->trig_insert_before_statement)
        return;

    LocTriggerData.type = T_TriggerData;
    LocTriggerData.tg_event = TRIGGER_EVENT_INSERT |
        TRIGGER_EVENT_BEFORE;
    LocTriggerData.tg_relation = relinfo->ri_RelationDesc;
    LocTriggerData.tg_trigtuple = NULL;
    LocTriggerData.tg_newtuple = NULL;
    LocTriggerData.tg_trigtuplebuf = InvalidBuffer;
    LocTriggerData.tg_newtuplebuf = InvalidBuffer;
    for (i = 0; i < trigdesc->numtriggers; i++)
    {
        Trigger    *trigger = &trigdesc->triggers[i];
        HeapTuple   newtuple;

        if (!TRIGGER_TYPE_MATCHES(trigger->tgtype,
                                  TRIGGER_TYPE_STATEMENT,
                                  TRIGGER_TYPE_BEFORE,
                                  TRIGGER_TYPE_INSERT))
            continue;
        if (!TriggerEnabled(estate, relinfo, trigger, LocTriggerData.tg_event,
                            NULL, NULL, NULL))
            continue;

        LocTriggerData.tg_trigger = trigger;
        newtuple = ExecCallTriggerFunc(&LocTriggerData,
                                       i,
                                       relinfo->ri_TrigFunctions,
                                       relinfo->ri_TrigInstrument,
                                       GetPerTupleMemoryContext(estate));

        if (newtuple)
            ereport(ERROR,
                    (errcode(ERRCODE_E_R_I_E_TRIGGER_PROTOCOL_VIOLATED),
                  errmsg("BEFORE STATEMENT trigger cannot return a value")));
    }
}

void
ExecASInsertTriggers(EState *estate, ResultRelInfo *relinfo)
{
    TriggerDesc *trigdesc = relinfo->ri_TrigDesc;

    if (trigdesc && trigdesc->trig_insert_after_statement)
        AfterTriggerSaveEvent(estate, relinfo, TRIGGER_EVENT_INSERT,
                              false, NULL, NULL, NIL, NULL);
}

TupleTableSlot *
ExecBRInsertTriggers(EState *estate, ResultRelInfo *relinfo,
                     TupleTableSlot *slot)
{
    TriggerDesc *trigdesc = relinfo->ri_TrigDesc;
    HeapTuple   slottuple = ExecMaterializeSlot(slot);
    HeapTuple   newtuple = slottuple;
    HeapTuple   oldtuple;
    TriggerData LocTriggerData;
    int         i;

    LocTriggerData.type = T_TriggerData;
    LocTriggerData.tg_event = TRIGGER_EVENT_INSERT |
        TRIGGER_EVENT_ROW |
        TRIGGER_EVENT_BEFORE;
    LocTriggerData.tg_relation = relinfo->ri_RelationDesc;
    LocTriggerData.tg_newtuple = NULL;
    LocTriggerData.tg_newtuplebuf = InvalidBuffer;
    for (i = 0; i < trigdesc->numtriggers; i++)
    {
        Trigger    *trigger = &trigdesc->triggers[i];

        if (!TRIGGER_TYPE_MATCHES(trigger->tgtype,
                                  TRIGGER_TYPE_ROW,
                                  TRIGGER_TYPE_BEFORE,
                                  TRIGGER_TYPE_INSERT))
            continue;
        if (!TriggerEnabled(estate, relinfo, trigger, LocTriggerData.tg_event,
                            NULL, NULL, newtuple))
            continue;

        LocTriggerData.tg_trigtuple = oldtuple = newtuple;
        LocTriggerData.tg_trigtuplebuf = InvalidBuffer;
        LocTriggerData.tg_trigger = trigger;
        newtuple = ExecCallTriggerFunc(&LocTriggerData,
                                       i,
                                       relinfo->ri_TrigFunctions,
                                       relinfo->ri_TrigInstrument,
                                       GetPerTupleMemoryContext(estate));
        if (oldtuple != newtuple && oldtuple != slottuple)
            heap_freetuple(oldtuple);
        if (newtuple == NULL)
            return NULL;        /* "do nothing" */
    }

    if (newtuple != slottuple)
    {
        /*
         * Return the modified tuple using the es_trig_tuple_slot.  We assume
         * the tuple was allocated in per-tuple memory context, and therefore
         * will go away by itself. The tuple table slot should not try to
         * clear it.
         */
        TupleTableSlot *newslot = estate->es_trig_tuple_slot;
        TupleDesc   tupdesc = RelationGetDescr(relinfo->ri_RelationDesc);

        if (newslot->tts_tupleDescriptor != tupdesc)
            ExecSetSlotDescriptor(newslot, tupdesc);
        ExecStoreTuple(newtuple, newslot, InvalidBuffer, false);
        slot = newslot;
    }
    return slot;
}

void
ExecARInsertTriggers(EState *estate, ResultRelInfo *relinfo,
                     HeapTuple trigtuple, List *recheckIndexes)
{
    TriggerDesc *trigdesc = relinfo->ri_TrigDesc;

    if (trigdesc && trigdesc->trig_insert_after_row)
        AfterTriggerSaveEvent(estate, relinfo, TRIGGER_EVENT_INSERT,
                              true, NULL, trigtuple, recheckIndexes, NULL);
}

TupleTableSlot *
ExecIRInsertTriggers(EState *estate, ResultRelInfo *relinfo,
                     TupleTableSlot *slot)
{
    TriggerDesc *trigdesc = relinfo->ri_TrigDesc;
    HeapTuple   slottuple = ExecMaterializeSlot(slot);
    HeapTuple   newtuple = slottuple;
    HeapTuple   oldtuple;
    TriggerData LocTriggerData;
    int         i;

    LocTriggerData.type = T_TriggerData;
    LocTriggerData.tg_event = TRIGGER_EVENT_INSERT |
        TRIGGER_EVENT_ROW |
        TRIGGER_EVENT_INSTEAD;
    LocTriggerData.tg_relation = relinfo->ri_RelationDesc;
    LocTriggerData.tg_newtuple = NULL;
    LocTriggerData.tg_newtuplebuf = InvalidBuffer;
    for (i = 0; i < trigdesc->numtriggers; i++)
    {
        Trigger    *trigger = &trigdesc->triggers[i];

        if (!TRIGGER_TYPE_MATCHES(trigger->tgtype,
                                  TRIGGER_TYPE_ROW,
                                  TRIGGER_TYPE_INSTEAD,
                                  TRIGGER_TYPE_INSERT))
            continue;
        if (!TriggerEnabled(estate, relinfo, trigger, LocTriggerData.tg_event,
                            NULL, NULL, newtuple))
            continue;

        LocTriggerData.tg_trigtuple = oldtuple = newtuple;
        LocTriggerData.tg_trigtuplebuf = InvalidBuffer;
        LocTriggerData.tg_trigger = trigger;
        newtuple = ExecCallTriggerFunc(&LocTriggerData,
                                       i,
                                       relinfo->ri_TrigFunctions,
                                       relinfo->ri_TrigInstrument,
                                       GetPerTupleMemoryContext(estate));
        if (oldtuple != newtuple && oldtuple != slottuple)
            heap_freetuple(oldtuple);
        if (newtuple == NULL)
            return NULL;        /* "do nothing" */
    }

    if (newtuple != slottuple)
    {
        /*
         * Return the modified tuple using the es_trig_tuple_slot.  We assume
         * the tuple was allocated in per-tuple memory context, and therefore
         * will go away by itself. The tuple table slot should not try to
         * clear it.
         */
        TupleTableSlot *newslot = estate->es_trig_tuple_slot;
        TupleDesc   tupdesc = RelationGetDescr(relinfo->ri_RelationDesc);

        if (newslot->tts_tupleDescriptor != tupdesc)
            ExecSetSlotDescriptor(newslot, tupdesc);
        ExecStoreTuple(newtuple, newslot, InvalidBuffer, false);
        slot = newslot;
    }
    return slot;
}

void
ExecBSDeleteTriggers(EState *estate, ResultRelInfo *relinfo)
{
    TriggerDesc *trigdesc;
    int         i;
    TriggerData LocTriggerData;

    trigdesc = relinfo->ri_TrigDesc;

    if (trigdesc == NULL)
        return;
    if (!trigdesc->trig_delete_before_statement)
        return;

    LocTriggerData.type = T_TriggerData;
    LocTriggerData.tg_event = TRIGGER_EVENT_DELETE |
        TRIGGER_EVENT_BEFORE;
    LocTriggerData.tg_relation = relinfo->ri_RelationDesc;
    LocTriggerData.tg_trigtuple = NULL;
    LocTriggerData.tg_newtuple = NULL;
    LocTriggerData.tg_trigtuplebuf = InvalidBuffer;
    LocTriggerData.tg_newtuplebuf = InvalidBuffer;
    for (i = 0; i < trigdesc->numtriggers; i++)
    {
        Trigger    *trigger = &trigdesc->triggers[i];
        HeapTuple   newtuple;

        if (!TRIGGER_TYPE_MATCHES(trigger->tgtype,
                                  TRIGGER_TYPE_STATEMENT,
                                  TRIGGER_TYPE_BEFORE,
                                  TRIGGER_TYPE_DELETE))
            continue;
        if (!TriggerEnabled(estate, relinfo, trigger, LocTriggerData.tg_event,
                            NULL, NULL, NULL))
            continue;

        LocTriggerData.tg_trigger = trigger;
        newtuple = ExecCallTriggerFunc(&LocTriggerData,
                                       i,
                                       relinfo->ri_TrigFunctions,
                                       relinfo->ri_TrigInstrument,
                                       GetPerTupleMemoryContext(estate));

        if (newtuple)
            ereport(ERROR,
                    (errcode(ERRCODE_E_R_I_E_TRIGGER_PROTOCOL_VIOLATED),
                  errmsg("BEFORE STATEMENT trigger cannot return a value")));
    }
}

void
ExecASDeleteTriggers(EState *estate, ResultRelInfo *relinfo)
{
    TriggerDesc *trigdesc = relinfo->ri_TrigDesc;

    if (trigdesc && trigdesc->trig_delete_after_statement)
        AfterTriggerSaveEvent(estate, relinfo, TRIGGER_EVENT_DELETE,
                              false, NULL, NULL, NIL, NULL);
}

bool
ExecBRDeleteTriggers(EState *estate, EPQState *epqstate,
                     ResultRelInfo *relinfo,
                     ItemPointer tupleid,
                     HeapTuple fdw_trigtuple)
{
    TriggerDesc *trigdesc = relinfo->ri_TrigDesc;
    bool        result = true;
    TriggerData LocTriggerData;
    HeapTuple   trigtuple;
    HeapTuple   newtuple;
    TupleTableSlot *newSlot;
    int         i;

    Assert(HeapTupleIsValid(fdw_trigtuple) ^ ItemPointerIsValid(tupleid));
    if (fdw_trigtuple == NULL)
    {
        trigtuple = GetTupleForTrigger(estate, epqstate, relinfo, tupleid,
                                       LockTupleExclusive, &newSlot);
        if (trigtuple == NULL)
            return false;
    }
    else
        trigtuple = fdw_trigtuple;

    LocTriggerData.type = T_TriggerData;
    LocTriggerData.tg_event = TRIGGER_EVENT_DELETE |
        TRIGGER_EVENT_ROW |
        TRIGGER_EVENT_BEFORE;
    LocTriggerData.tg_relation = relinfo->ri_RelationDesc;
    LocTriggerData.tg_newtuple = NULL;
    LocTriggerData.tg_newtuplebuf = InvalidBuffer;
    for (i = 0; i < trigdesc->numtriggers; i++)
    {
        Trigger    *trigger = &trigdesc->triggers[i];

        if (!TRIGGER_TYPE_MATCHES(trigger->tgtype,
                                  TRIGGER_TYPE_ROW,
                                  TRIGGER_TYPE_BEFORE,
                                  TRIGGER_TYPE_DELETE))
            continue;
        if (!TriggerEnabled(estate, relinfo, trigger, LocTriggerData.tg_event,
                            NULL, trigtuple, NULL))
            continue;

        LocTriggerData.tg_trigtuple = trigtuple;
        LocTriggerData.tg_trigtuplebuf = InvalidBuffer;
        LocTriggerData.tg_trigger = trigger;
        newtuple = ExecCallTriggerFunc(&LocTriggerData,
                                       i,
                                       relinfo->ri_TrigFunctions,
                                       relinfo->ri_TrigInstrument,
                                       GetPerTupleMemoryContext(estate));
        if (newtuple == NULL)
        {
            result = false;     /* tell caller to suppress delete */
            break;
        }
        if (newtuple != trigtuple)
            heap_freetuple(newtuple);
    }
    if (trigtuple != fdw_trigtuple)
        heap_freetuple(trigtuple);

    return result;
}

void
ExecARDeleteTriggers(EState *estate, ResultRelInfo *relinfo,
                     ItemPointer tupleid,
                     HeapTuple fdw_trigtuple)
{
    TriggerDesc *trigdesc = relinfo->ri_TrigDesc;

    if (trigdesc && trigdesc->trig_delete_after_row)
    {
        HeapTuple   trigtuple;

        Assert(HeapTupleIsValid(fdw_trigtuple) ^ ItemPointerIsValid(tupleid));
        if (fdw_trigtuple == NULL)
            trigtuple = GetTupleForTrigger(estate,
                                           NULL,
                                           relinfo,
                                           tupleid,
                                           LockTupleExclusive,
                                           NULL);
        else
            trigtuple = fdw_trigtuple;

        AfterTriggerSaveEvent(estate, relinfo, TRIGGER_EVENT_DELETE,
                              true, trigtuple, NULL, NIL, NULL);
        if (trigtuple != fdw_trigtuple)
            heap_freetuple(trigtuple);
    }
}

bool
ExecIRDeleteTriggers(EState *estate, ResultRelInfo *relinfo,
                     HeapTuple trigtuple)
{
    TriggerDesc *trigdesc = relinfo->ri_TrigDesc;
    TriggerData LocTriggerData;
    HeapTuple   rettuple;
    int         i;

    LocTriggerData.type = T_TriggerData;
    LocTriggerData.tg_event = TRIGGER_EVENT_DELETE |
        TRIGGER_EVENT_ROW |
        TRIGGER_EVENT_INSTEAD;
    LocTriggerData.tg_relation = relinfo->ri_RelationDesc;
    LocTriggerData.tg_newtuple = NULL;
    LocTriggerData.tg_newtuplebuf = InvalidBuffer;
    for (i = 0; i < trigdesc->numtriggers; i++)
    {
        Trigger    *trigger = &trigdesc->triggers[i];

        if (!TRIGGER_TYPE_MATCHES(trigger->tgtype,
                                  TRIGGER_TYPE_ROW,
                                  TRIGGER_TYPE_INSTEAD,
                                  TRIGGER_TYPE_DELETE))
            continue;
        if (!TriggerEnabled(estate, relinfo, trigger, LocTriggerData.tg_event,
                            NULL, trigtuple, NULL))
            continue;

        LocTriggerData.tg_trigtuple = trigtuple;
        LocTriggerData.tg_trigtuplebuf = InvalidBuffer;
        LocTriggerData.tg_trigger = trigger;
        rettuple = ExecCallTriggerFunc(&LocTriggerData,
                                       i,
                                       relinfo->ri_TrigFunctions,
                                       relinfo->ri_TrigInstrument,
                                       GetPerTupleMemoryContext(estate));
        if (rettuple == NULL)
            return false;       /* Delete was suppressed */
        if (rettuple != trigtuple)
            heap_freetuple(rettuple);
    }
    return true;
}

void
ExecBSUpdateTriggers(EState *estate, ResultRelInfo *relinfo)
{
    TriggerDesc *trigdesc;
    int         i;
    TriggerData LocTriggerData;
    Bitmapset  *updatedCols;

    trigdesc = relinfo->ri_TrigDesc;

    if (trigdesc == NULL)
        return;
    if (!trigdesc->trig_update_before_statement)
        return;

    updatedCols = GetUpdatedColumns(relinfo, estate);

    LocTriggerData.type = T_TriggerData;
    LocTriggerData.tg_event = TRIGGER_EVENT_UPDATE |
        TRIGGER_EVENT_BEFORE;
    LocTriggerData.tg_relation = relinfo->ri_RelationDesc;
    LocTriggerData.tg_trigtuple = NULL;
    LocTriggerData.tg_newtuple = NULL;
    LocTriggerData.tg_trigtuplebuf = InvalidBuffer;
    LocTriggerData.tg_newtuplebuf = InvalidBuffer;
    for (i = 0; i < trigdesc->numtriggers; i++)
    {
        Trigger    *trigger = &trigdesc->triggers[i];
        HeapTuple   newtuple;

        if (!TRIGGER_TYPE_MATCHES(trigger->tgtype,
                                  TRIGGER_TYPE_STATEMENT,
                                  TRIGGER_TYPE_BEFORE,
                                  TRIGGER_TYPE_UPDATE))
            continue;
        if (!TriggerEnabled(estate, relinfo, trigger, LocTriggerData.tg_event,
                            updatedCols, NULL, NULL))
            continue;

        LocTriggerData.tg_trigger = trigger;
        newtuple = ExecCallTriggerFunc(&LocTriggerData,
                                       i,
                                       relinfo->ri_TrigFunctions,
                                       relinfo->ri_TrigInstrument,
                                       GetPerTupleMemoryContext(estate));

        if (newtuple)
            ereport(ERROR,
                    (errcode(ERRCODE_E_R_I_E_TRIGGER_PROTOCOL_VIOLATED),
                  errmsg("BEFORE STATEMENT trigger cannot return a value")));
    }
}

void
ExecASUpdateTriggers(EState *estate, ResultRelInfo *relinfo)
{
    TriggerDesc *trigdesc = relinfo->ri_TrigDesc;

    if (trigdesc && trigdesc->trig_update_after_statement)
        AfterTriggerSaveEvent(estate, relinfo, TRIGGER_EVENT_UPDATE,
                              false, NULL, NULL, NIL,
                              GetUpdatedColumns(relinfo, estate));
}

TupleTableSlot *
ExecBRUpdateTriggers(EState *estate, EPQState *epqstate,
                     ResultRelInfo *relinfo,
                     ItemPointer tupleid,
                     HeapTuple fdw_trigtuple,
                     TupleTableSlot *slot)
{
    TriggerDesc *trigdesc = relinfo->ri_TrigDesc;
    HeapTuple   slottuple = ExecMaterializeSlot(slot);
    HeapTuple   newtuple = slottuple;
    TriggerData LocTriggerData;
    HeapTuple   trigtuple;
    HeapTuple   oldtuple;
    TupleTableSlot *newSlot;
    int         i;
    Bitmapset  *updatedCols;
    LockTupleMode lockmode;

    /* Determine lock mode to use */
    lockmode = ExecUpdateLockMode(estate, relinfo);

    Assert(HeapTupleIsValid(fdw_trigtuple) ^ ItemPointerIsValid(tupleid));
    if (fdw_trigtuple == NULL)
    {
        /* get a copy of the on-disk tuple we are planning to update */
        trigtuple = GetTupleForTrigger(estate, epqstate, relinfo, tupleid,
                                       lockmode, &newSlot);
        if (trigtuple == NULL)
            return NULL;        /* cancel the update action */
    }
    else
    {
        trigtuple = fdw_trigtuple;
        newSlot = NULL;
    }

    /*
     * In READ COMMITTED isolation level it's possible that target tuple was
     * changed due to concurrent update.  In that case we have a raw subplan
     * output tuple in newSlot, and need to run it through the junk filter to
     * produce an insertable tuple.
     *
     * Caution: more than likely, the passed-in slot is the same as the
     * junkfilter's output slot, so we are clobbering the original value of
     * slottuple by doing the filtering.  This is OK since neither we nor our
     * caller have any more interest in the prior contents of that slot.
     */
    if (newSlot != NULL)
    {
        slot = ExecFilterJunk(relinfo->ri_junkFilter, newSlot);
        slottuple = ExecMaterializeSlot(slot);
        newtuple = slottuple;
    }


    LocTriggerData.type = T_TriggerData;
    LocTriggerData.tg_event = TRIGGER_EVENT_UPDATE |
        TRIGGER_EVENT_ROW |
        TRIGGER_EVENT_BEFORE;
    LocTriggerData.tg_relation = relinfo->ri_RelationDesc;
    updatedCols = GetUpdatedColumns(relinfo, estate);
    for (i = 0; i < trigdesc->numtriggers; i++)
    {
        Trigger    *trigger = &trigdesc->triggers[i];

        if (!TRIGGER_TYPE_MATCHES(trigger->tgtype,
                                  TRIGGER_TYPE_ROW,
                                  TRIGGER_TYPE_BEFORE,
                                  TRIGGER_TYPE_UPDATE))
            continue;
        if (!TriggerEnabled(estate, relinfo, trigger, LocTriggerData.tg_event,
                            updatedCols, trigtuple, newtuple))
            continue;

        LocTriggerData.tg_trigtuple = trigtuple;
        LocTriggerData.tg_newtuple = oldtuple = newtuple;
        LocTriggerData.tg_trigtuplebuf = InvalidBuffer;
        LocTriggerData.tg_newtuplebuf = InvalidBuffer;
        LocTriggerData.tg_trigger = trigger;
        newtuple = ExecCallTriggerFunc(&LocTriggerData,
                                       i,
                                       relinfo->ri_TrigFunctions,
                                       relinfo->ri_TrigInstrument,
                                       GetPerTupleMemoryContext(estate));
        if (oldtuple != newtuple && oldtuple != slottuple)
            heap_freetuple(oldtuple);
        if (newtuple == NULL)
        {
            if (trigtuple != fdw_trigtuple)
                heap_freetuple(trigtuple);
            return NULL;        /* "do nothing" */
        }
    }
    if (trigtuple != fdw_trigtuple)
        heap_freetuple(trigtuple);

    if (newtuple != slottuple)
    {
        /*
         * Return the modified tuple using the es_trig_tuple_slot.  We assume
         * the tuple was allocated in per-tuple memory context, and therefore
         * will go away by itself. The tuple table slot should not try to
         * clear it.
         */
        TupleTableSlot *newslot = estate->es_trig_tuple_slot;
        TupleDesc   tupdesc = RelationGetDescr(relinfo->ri_RelationDesc);

        if (newslot->tts_tupleDescriptor != tupdesc)
            ExecSetSlotDescriptor(newslot, tupdesc);
        ExecStoreTuple(newtuple, newslot, InvalidBuffer, false);
        slot = newslot;
    }
    return slot;
}

void
ExecARUpdateTriggers(EState *estate, ResultRelInfo *relinfo,
                     ItemPointer tupleid,
                     HeapTuple fdw_trigtuple,
                     HeapTuple newtuple,
                     List *recheckIndexes)
{
    TriggerDesc *trigdesc = relinfo->ri_TrigDesc;

    if (trigdesc && trigdesc->trig_update_after_row)
    {
        HeapTuple   trigtuple;

        Assert(HeapTupleIsValid(fdw_trigtuple) ^ ItemPointerIsValid(tupleid));
        if (fdw_trigtuple == NULL)
            trigtuple = GetTupleForTrigger(estate,
                                           NULL,
                                           relinfo,
                                           tupleid,
                                           LockTupleExclusive,
                                           NULL);
        else
            trigtuple = fdw_trigtuple;

        AfterTriggerSaveEvent(estate, relinfo, TRIGGER_EVENT_UPDATE,
                              true, trigtuple, newtuple, recheckIndexes,
                              GetUpdatedColumns(relinfo, estate));
        if (trigtuple != fdw_trigtuple)
            heap_freetuple(trigtuple);
    }
}

TupleTableSlot *
ExecIRUpdateTriggers(EState *estate, ResultRelInfo *relinfo,
                     HeapTuple trigtuple, TupleTableSlot *slot)
{
    TriggerDesc *trigdesc = relinfo->ri_TrigDesc;
    HeapTuple   slottuple = ExecMaterializeSlot(slot);
    HeapTuple   newtuple = slottuple;
    TriggerData LocTriggerData;
    HeapTuple   oldtuple;
    int         i;

    LocTriggerData.type = T_TriggerData;
    LocTriggerData.tg_event = TRIGGER_EVENT_UPDATE |
        TRIGGER_EVENT_ROW |
        TRIGGER_EVENT_INSTEAD;
    LocTriggerData.tg_relation = relinfo->ri_RelationDesc;
    for (i = 0; i < trigdesc->numtriggers; i++)
    {
        Trigger    *trigger = &trigdesc->triggers[i];

        if (!TRIGGER_TYPE_MATCHES(trigger->tgtype,
                                  TRIGGER_TYPE_ROW,
                                  TRIGGER_TYPE_INSTEAD,
                                  TRIGGER_TYPE_UPDATE))
            continue;
        if (!TriggerEnabled(estate, relinfo, trigger, LocTriggerData.tg_event,
                            NULL, trigtuple, newtuple))
            continue;

        LocTriggerData.tg_trigtuple = trigtuple;
        LocTriggerData.tg_newtuple = oldtuple = newtuple;
        LocTriggerData.tg_trigtuplebuf = InvalidBuffer;
        LocTriggerData.tg_newtuplebuf = InvalidBuffer;
        LocTriggerData.tg_trigger = trigger;
        newtuple = ExecCallTriggerFunc(&LocTriggerData,
                                       i,
                                       relinfo->ri_TrigFunctions,
                                       relinfo->ri_TrigInstrument,
                                       GetPerTupleMemoryContext(estate));
        if (oldtuple != newtuple && oldtuple != slottuple)
            heap_freetuple(oldtuple);
        if (newtuple == NULL)
            return NULL;        /* "do nothing" */
    }

    if (newtuple != slottuple)
    {
        /*
         * Return the modified tuple using the es_trig_tuple_slot.  We assume
         * the tuple was allocated in per-tuple memory context, and therefore
         * will go away by itself. The tuple table slot should not try to
         * clear it.
         */
        TupleTableSlot *newslot = estate->es_trig_tuple_slot;
        TupleDesc   tupdesc = RelationGetDescr(relinfo->ri_RelationDesc);

        if (newslot->tts_tupleDescriptor != tupdesc)
            ExecSetSlotDescriptor(newslot, tupdesc);
        ExecStoreTuple(newtuple, newslot, InvalidBuffer, false);
        slot = newslot;
    }
    return slot;
}

void
ExecBSTruncateTriggers(EState *estate, ResultRelInfo *relinfo)
{
    TriggerDesc *trigdesc;
    int         i;
    TriggerData LocTriggerData;

    trigdesc = relinfo->ri_TrigDesc;

    if (trigdesc == NULL)
        return;
    if (!trigdesc->trig_truncate_before_statement)
        return;

    LocTriggerData.type = T_TriggerData;
    LocTriggerData.tg_event = TRIGGER_EVENT_TRUNCATE |
        TRIGGER_EVENT_BEFORE;
    LocTriggerData.tg_relation = relinfo->ri_RelationDesc;
    LocTriggerData.tg_trigtuple = NULL;
    LocTriggerData.tg_newtuple = NULL;
    LocTriggerData.tg_trigtuplebuf = InvalidBuffer;
    LocTriggerData.tg_newtuplebuf = InvalidBuffer;
    for (i = 0; i < trigdesc->numtriggers; i++)
    {
        Trigger    *trigger = &trigdesc->triggers[i];
        HeapTuple   newtuple;

        if (!TRIGGER_TYPE_MATCHES(trigger->tgtype,
                                  TRIGGER_TYPE_STATEMENT,
                                  TRIGGER_TYPE_BEFORE,
                                  TRIGGER_TYPE_TRUNCATE))
            continue;
        if (!TriggerEnabled(estate, relinfo, trigger, LocTriggerData.tg_event,
                            NULL, NULL, NULL))
            continue;

        LocTriggerData.tg_trigger = trigger;
        newtuple = ExecCallTriggerFunc(&LocTriggerData,
                                       i,
                                       relinfo->ri_TrigFunctions,
                                       relinfo->ri_TrigInstrument,
                                       GetPerTupleMemoryContext(estate));

        if (newtuple)
            ereport(ERROR,
                    (errcode(ERRCODE_E_R_I_E_TRIGGER_PROTOCOL_VIOLATED),
                  errmsg("BEFORE STATEMENT trigger cannot return a value")));
    }
}

void
ExecASTruncateTriggers(EState *estate, ResultRelInfo *relinfo)
{
    TriggerDesc *trigdesc = relinfo->ri_TrigDesc;

    if (trigdesc && trigdesc->trig_truncate_after_statement)
        AfterTriggerSaveEvent(estate, relinfo, TRIGGER_EVENT_TRUNCATE,
                              false, NULL, NULL, NIL, NULL);
}


static HeapTuple
GetTupleForTrigger(EState *estate,
                   EPQState *epqstate,
                   ResultRelInfo *relinfo,
                   ItemPointer tid,
                   LockTupleMode lockmode,
                   TupleTableSlot **newSlot)
{
    Relation    relation = relinfo->ri_RelationDesc;
    HeapTupleData tuple;
    HeapTuple   result;
    Buffer      buffer;

    if (newSlot != NULL)
    {
        HTSU_Result test;
        HeapUpdateFailureData hufd;

        *newSlot = NULL;

        /* caller must pass an epqstate if EvalPlanQual is possible */
        Assert(epqstate != NULL);

        /*
         * lock tuple for update
         */
ltrmark:;
        tuple.t_self = *tid;
        test = heap_lock_tuple(relation, &tuple,
                               estate->es_output_cid,
                               lockmode, LockWaitBlock,
                               false, &buffer, &hufd);
        switch (test)
        {
            case HeapTupleSelfUpdated:

                /*
                 * The target tuple was already updated or deleted by the
                 * current command, or by a later command in the current
                 * transaction.  We ignore the tuple in the former case, and
                 * throw error in the latter case, for the same reasons
                 * enumerated in ExecUpdate and ExecDelete in
                 * nodeModifyTable.c.
                 */
                if (hufd.cmax != estate->es_output_cid)
                    ereport(ERROR,
                            (errcode(ERRCODE_TRIGGERED_DATA_CHANGE_VIOLATION),
                             errmsg("tuple to be updated was already modified by an operation triggered by the current command"),
                             errhint("Consider using an AFTER trigger instead of a BEFORE trigger to propagate changes to other rows.")));

                /* treat it as deleted; do not process */
                ReleaseBuffer(buffer);
                return NULL;

            case HeapTupleMayBeUpdated:
                break;

            case HeapTupleUpdated:
                ReleaseBuffer(buffer);
                if (IsolationUsesXactSnapshot())
                    ereport(ERROR,
                            (errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
                             errmsg("could not serialize access due to concurrent update")));
                if (!ItemPointerEquals(&hufd.ctid, &tuple.t_self))
                {
                    /* it was updated, so look at the updated version */
                    TupleTableSlot *epqslot;

                    epqslot = EvalPlanQual(estate,
                                           epqstate,
                                           relation,
                                           relinfo->ri_RangeTableIndex,
                                           lockmode,
                                           &hufd.ctid,
                                           hufd.xmax);
                    if (!TupIsNull(epqslot))
                    {
                        *tid = hufd.ctid;
                        *newSlot = epqslot;

                        /*
                         * EvalPlanQual already locked the tuple, but we
                         * re-call heap_lock_tuple anyway as an easy way of
                         * re-fetching the correct tuple.  Speed is hardly a
                         * criterion in this path anyhow.
                         */
                        goto ltrmark;
                    }
                }

                /*
                 * if tuple was deleted or PlanQual failed for updated tuple -
                 * we must not process this tuple!
                 */
                return NULL;

            case HeapTupleInvisible:
                elog(ERROR, "attempted to lock invisible tuple");

            default:
                ReleaseBuffer(buffer);
                elog(ERROR, "unrecognized heap_lock_tuple status: %u", test);
                return NULL;    /* keep compiler quiet */
        }
    }
    else
    {
        Page        page;
        ItemId      lp;

        buffer = ReadBuffer(relation, ItemPointerGetBlockNumber(tid));

        /*
         * Although we already know this tuple is valid, we must lock the
         * buffer to ensure that no one has a buffer cleanup lock; otherwise
         * they might move the tuple while we try to copy it.  But we can
         * release the lock before actually doing the heap_copytuple call,
         * since holding pin is sufficient to prevent anyone from getting a
         * cleanup lock they don't already hold.
         */
        LockBuffer(buffer, BUFFER_LOCK_SHARE);

        page = BufferGetPage(buffer);
        lp = PageGetItemId(page, ItemPointerGetOffsetNumber(tid));

        Assert(ItemIdIsNormal(lp));

        tuple.t_data = (HeapTupleHeader) PageGetItem(page, lp);
        tuple.t_len = ItemIdGetLength(lp);
        tuple.t_self = *tid;
        tuple.t_tableOid = RelationGetRelid(relation);

        LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
    }

    result = heap_copytuple(&tuple);
    ReleaseBuffer(buffer);

    return result;
}

/*
 * Is trigger enabled to fire?
 */
static bool
TriggerEnabled(EState *estate, ResultRelInfo *relinfo,
               Trigger *trigger, TriggerEvent event,
               Bitmapset *modifiedCols,
               HeapTuple oldtup, HeapTuple newtup)
{
    /* Check replication-role-dependent enable state */
    if (SessionReplicationRole == SESSION_REPLICATION_ROLE_REPLICA)
    {
        if (trigger->tgenabled == TRIGGER_FIRES_ON_ORIGIN ||
            trigger->tgenabled == TRIGGER_DISABLED)
            return false;
    }
    else    /* ORIGIN or LOCAL role */
    {
        if (trigger->tgenabled == TRIGGER_FIRES_ON_REPLICA ||
            trigger->tgenabled == TRIGGER_DISABLED)
            return false;
    }

    /*
     * Check for column-specific trigger (only possible for UPDATE, and in
     * fact we *must* ignore tgattr for other event types)
     */
    if (trigger->tgnattr > 0 && TRIGGER_FIRED_BY_UPDATE(event))
    {
        int         i;
        bool        modified;

        modified = false;
        for (i = 0; i < trigger->tgnattr; i++)
        {
            if (bms_is_member(trigger->tgattr[i] - FirstLowInvalidHeapAttributeNumber,
                              modifiedCols))
            {
                modified = true;
                break;
            }
        }
        if (!modified)
            return false;
    }

    /* Check for WHEN clause */
    if (trigger->tgqual)
    {
        TupleDesc   tupdesc = RelationGetDescr(relinfo->ri_RelationDesc);
        List      **predicate;
        ExprContext *econtext;
        TupleTableSlot *oldslot = NULL;
        TupleTableSlot *newslot = NULL;
        MemoryContext oldContext;
        int         i;

        Assert(estate != NULL);

        /*
         * trigger is an element of relinfo->ri_TrigDesc->triggers[]; find the
         * matching element of relinfo->ri_TrigWhenExprs[]
         */
        i = trigger - relinfo->ri_TrigDesc->triggers;
        predicate = &relinfo->ri_TrigWhenExprs[i];

        /*
         * If first time through for this WHEN expression, build expression
         * nodetrees for it.  Keep them in the per-query memory context so
         * they'll survive throughout the query.
         */
        if (*predicate == NIL)
        {
            Node       *tgqual;

            oldContext = MemoryContextSwitchTo(estate->es_query_cxt);
            tgqual = stringToNode(trigger->tgqual);
            /* Change references to OLD and NEW to INNER_VAR and OUTER_VAR */
            ChangeVarNodes(tgqual, PRS2_OLD_VARNO, INNER_VAR, 0);
            ChangeVarNodes(tgqual, PRS2_NEW_VARNO, OUTER_VAR, 0);
            /* ExecQual wants implicit-AND form */
            tgqual = (Node *) make_ands_implicit((Expr *) tgqual);
            *predicate = (List *) ExecPrepareExpr((Expr *) tgqual, estate);
            MemoryContextSwitchTo(oldContext);
        }

        /*
         * We will use the EState's per-tuple context for evaluating WHEN
         * expressions (creating it if it's not already there).
         */
        econtext = GetPerTupleExprContext(estate);

        /*
         * Put OLD and NEW tuples into tupleslots for expression evaluation.
         * These slots can be shared across the whole estate, but be careful
         * that they have the current resultrel's tupdesc.
         */
        if (HeapTupleIsValid(oldtup))
        {
            if (estate->es_trig_oldtup_slot == NULL)
            {
                oldContext = MemoryContextSwitchTo(estate->es_query_cxt);
                estate->es_trig_oldtup_slot = ExecInitExtraTupleSlot(estate);
                MemoryContextSwitchTo(oldContext);
            }
            oldslot = estate->es_trig_oldtup_slot;
            if (oldslot->tts_tupleDescriptor != tupdesc)
                ExecSetSlotDescriptor(oldslot, tupdesc);
            ExecStoreTuple(oldtup, oldslot, InvalidBuffer, false);
        }
        if (HeapTupleIsValid(newtup))
        {
            if (estate->es_trig_newtup_slot == NULL)
            {
                oldContext = MemoryContextSwitchTo(estate->es_query_cxt);
                estate->es_trig_newtup_slot = ExecInitExtraTupleSlot(estate);
                MemoryContextSwitchTo(oldContext);
            }
            newslot = estate->es_trig_newtup_slot;
            if (newslot->tts_tupleDescriptor != tupdesc)
                ExecSetSlotDescriptor(newslot, tupdesc);
            ExecStoreTuple(newtup, newslot, InvalidBuffer, false);
        }

        /*
         * Finally evaluate the expression, making the old and/or new tuples
         * available as INNER_VAR/OUTER_VAR respectively.
         */
        econtext->ecxt_innertuple = oldslot;
        econtext->ecxt_outertuple = newslot;
        if (!ExecQual(*predicate, econtext, false))
            return false;
    }

    return true;
}


/* ----------
 * After-trigger stuff
 *
 * The AfterTriggersData struct holds data about pending AFTER trigger events
 * during the current transaction tree.  (BEFORE triggers are fired
 * immediately so we don't need any persistent state about them.)  The struct
 * and most of its subsidiary data are kept in TopTransactionContext; however
 * the individual event records are kept in a separate sub-context.  This is
 * done mainly so that it's easy to tell from a memory context dump how much
 * space is being eaten by trigger events.
 *
 * Because the list of pending events can grow large, we go to some
 * considerable effort to minimize per-event memory consumption.  The event
 * records are grouped into chunks and common data for similar events in the
 * same chunk is only stored once.
 *
 * XXX We need to be able to save the per-event data in a file if it grows too
 * large.
 * ----------
 */

/* Per-trigger SET CONSTRAINT status */
typedef struct SetConstraintTriggerData
{
    Oid         sct_tgoid;
    bool        sct_tgisdeferred;
} SetConstraintTriggerData;

typedef struct SetConstraintTriggerData *SetConstraintTrigger;

/*
 * SET CONSTRAINT intra-transaction status.
 *
 * We make this a single palloc'd object so it can be copied and freed easily.
 *
 * all_isset and all_isdeferred are used to keep track
 * of SET CONSTRAINTS ALL {DEFERRED, IMMEDIATE}.
 *
 * trigstates[] stores per-trigger tgisdeferred settings.
 */
typedef struct SetConstraintStateData
{
    bool        all_isset;
    bool        all_isdeferred;
    int         numstates;      /* number of trigstates[] entries in use */
    int         numalloc;       /* allocated size of trigstates[] */
    SetConstraintTriggerData trigstates[FLEXIBLE_ARRAY_MEMBER];
} SetConstraintStateData;

typedef SetConstraintStateData *SetConstraintState;


/*
 * Per-trigger-event data
 *
 * The actual per-event data, AfterTriggerEventData, includes DONE/IN_PROGRESS
 * status bits and up to two tuple CTIDs.  Each event record also has an
 * associated AfterTriggerSharedData that is shared across all instances of
 * similar events within a "chunk".
 *
 * For row-level triggers, we arrange not to waste storage on unneeded ctid
 * fields.  Updates of regular tables use two; inserts and deletes of regular
 * tables use one; foreign tables always use zero and save the tuple(s) to a
 * tuplestore.  AFTER_TRIGGER_FDW_FETCH directs AfterTriggerExecute() to
 * retrieve a fresh tuple or pair of tuples from that tuplestore, while
 * AFTER_TRIGGER_FDW_REUSE directs it to use the most-recently-retrieved
 * tuple(s).  This permits storing tuples once regardless of the number of
 * row-level triggers on a foreign table.
 *
 * Statement-level triggers always bear AFTER_TRIGGER_1CTID, though they
 * require no ctid field.  We lack the flag bit space to neatly represent that
 * distinct case, and it seems unlikely to be worth much trouble.
 *
 * Note: ats_firing_id is initially zero and is set to something else when
 * AFTER_TRIGGER_IN_PROGRESS is set.  It indicates which trigger firing
 * cycle the trigger will be fired in (or was fired in, if DONE is set).
 * Although this is mutable state, we can keep it in AfterTriggerSharedData
 * because all instances of the same type of event in a given event list will
 * be fired at the same time, if they were queued between the same firing
 * cycles.  So we need only ensure that ats_firing_id is zero when attaching
 * a new event to an existing AfterTriggerSharedData record.
 */
typedef uint32 TriggerFlags;

#define AFTER_TRIGGER_OFFSET            0x0FFFFFFF      /* must be low-order
                                                         * bits */
#define AFTER_TRIGGER_DONE              0x10000000
#define AFTER_TRIGGER_IN_PROGRESS       0x20000000
/* bits describing the size and tuple sources of this event */
#define AFTER_TRIGGER_FDW_REUSE         0x00000000
#define AFTER_TRIGGER_FDW_FETCH         0x80000000
#define AFTER_TRIGGER_1CTID             0x40000000
#define AFTER_TRIGGER_2CTID             0xC0000000
#define AFTER_TRIGGER_TUP_BITS          0xC0000000

typedef struct AfterTriggerSharedData *AfterTriggerShared;

typedef struct AfterTriggerSharedData
{
    TriggerEvent ats_event;     /* event type indicator, see trigger.h */
    Oid         ats_tgoid;      /* the trigger's ID */
    Oid         ats_relid;      /* the relation it's on */
    CommandId   ats_firing_id;  /* ID for firing cycle */
} AfterTriggerSharedData;

typedef struct AfterTriggerEventData *AfterTriggerEvent;

typedef struct AfterTriggerEventData
{
    TriggerFlags ate_flags;     /* status bits and offset to shared data */
    ItemPointerData ate_ctid1;  /* inserted, deleted, or old updated tuple */
    ItemPointerData ate_ctid2;  /* new updated tuple */
} AfterTriggerEventData;

/* AfterTriggerEventData, minus ate_ctid2 */
typedef struct AfterTriggerEventDataOneCtid
{
    TriggerFlags ate_flags;     /* status bits and offset to shared data */
    ItemPointerData ate_ctid1;  /* inserted, deleted, or old updated tuple */
}   AfterTriggerEventDataOneCtid;

/* AfterTriggerEventData, minus ate_ctid1 and ate_ctid2 */
typedef struct AfterTriggerEventDataZeroCtids
{
    TriggerFlags ate_flags;     /* status bits and offset to shared data */
}   AfterTriggerEventDataZeroCtids;

#define SizeofTriggerEvent(evt) \
    (((evt)->ate_flags & AFTER_TRIGGER_TUP_BITS) == AFTER_TRIGGER_2CTID ? \
     sizeof(AfterTriggerEventData) : \
        ((evt)->ate_flags & AFTER_TRIGGER_TUP_BITS) == AFTER_TRIGGER_1CTID ? \
        sizeof(AfterTriggerEventDataOneCtid) : \
            sizeof(AfterTriggerEventDataZeroCtids))

#define GetTriggerSharedData(evt) \
    ((AfterTriggerShared) ((char *) (evt) + ((evt)->ate_flags & AFTER_TRIGGER_OFFSET)))

/*
 * To avoid palloc overhead, we keep trigger events in arrays in successively-
 * larger chunks (a slightly more sophisticated version of an expansible
 * array).  The space between CHUNK_DATA_START and freeptr is occupied by
 * AfterTriggerEventData records; the space between endfree and endptr is
 * occupied by AfterTriggerSharedData records.
 */
typedef struct AfterTriggerEventChunk
{
    struct AfterTriggerEventChunk *next;        /* list link */
    char       *freeptr;        /* start of free space in chunk */
    char       *endfree;        /* end of free space in chunk */
    char       *endptr;         /* end of chunk */
    /* event data follows here */
} AfterTriggerEventChunk;

#define CHUNK_DATA_START(cptr) ((char *) (cptr) + MAXALIGN(sizeof(AfterTriggerEventChunk)))

/* A list of events */
typedef struct AfterTriggerEventList
{
    AfterTriggerEventChunk *head;
    AfterTriggerEventChunk *tail;
    char       *tailfree;       /* freeptr of tail chunk */
} AfterTriggerEventList;

/* Macros to help in iterating over a list of events */
#define for_each_chunk(cptr, evtlist) \
    for (cptr = (evtlist).head; cptr != NULL; cptr = cptr->next)
#define for_each_event(eptr, cptr) \
    for (eptr = (AfterTriggerEvent) CHUNK_DATA_START(cptr); \
         (char *) eptr < (cptr)->freeptr; \
         eptr = (AfterTriggerEvent) (((char *) eptr) + SizeofTriggerEvent(eptr)))
/* Use this if no special per-chunk processing is needed */
#define for_each_event_chunk(eptr, cptr, evtlist) \
    for_each_chunk(cptr, evtlist) for_each_event(eptr, cptr)


/*
 * All per-transaction data for the AFTER TRIGGERS module.
 *
 * AfterTriggersData has the following fields:
 *
 * firing_counter is incremented for each call of afterTriggerInvokeEvents.
 * We mark firable events with the current firing cycle's ID so that we can
 * tell which ones to work on.  This ensures sane behavior if a trigger
 * function chooses to do SET CONSTRAINTS: the inner SET CONSTRAINTS will
 * only fire those events that weren't already scheduled for firing.
 *
 * state keeps track of the transaction-local effects of SET CONSTRAINTS.
 * This is saved and restored across failed subtransactions.
 *
 * events is the current list of deferred events.  This is global across
 * all subtransactions of the current transaction.  In a subtransaction
 * abort, we know that the events added by the subtransaction are at the
 * end of the list, so it is relatively easy to discard them.  The event
 * list chunks themselves are stored in event_cxt.
 *
 * query_depth is the current depth of nested AfterTriggerBeginQuery calls
 * (-1 when the stack is empty).
 *
 * query_stack[query_depth] is a list of AFTER trigger events queued by the
 * current query (and the query_stack entries below it are lists of trigger
 * events queued by calling queries).  None of these are valid until the
 * matching AfterTriggerEndQuery call occurs.  At that point we fire
 * immediate-mode triggers, and append any deferred events to the main events
 * list.
 *
 * fdw_tuplestores[query_depth] is a tuplestore containing the foreign tuples
 * needed for the current query.
 *
 * maxquerydepth is just the allocated length of query_stack and
 * fdw_tuplestores.
 *
 * state_stack is a stack of pointers to saved copies of the SET CONSTRAINTS
 * state data; each subtransaction level that modifies that state first
 * saves a copy, which we use to restore the state if we abort.
 *
 * events_stack is a stack of copies of the events head/tail pointers,
 * which we use to restore those values during subtransaction abort.
 *
 * depth_stack is a stack of copies of subtransaction-start-time query_depth,
 * which we similarly use to clean up at subtransaction abort.
 *
 * firing_stack is a stack of copies of subtransaction-start-time
 * firing_counter.  We use this to recognize which deferred triggers were
 * fired (or marked for firing) within an aborted subtransaction.
 *
 * We use GetCurrentTransactionNestLevel() to determine the correct array
 * index in these stacks.  maxtransdepth is the number of allocated entries in
 * each stack.  (By not keeping our own stack pointer, we can avoid trouble
 * in cases where errors during subxact abort cause multiple invocations
 * of AfterTriggerEndSubXact() at the same nesting depth.)
 */
typedef struct AfterTriggersData
{
    CommandId   firing_counter; /* next firing ID to assign */
    SetConstraintState state;   /* the active S C state */
    AfterTriggerEventList events;       /* deferred-event list */
    int         query_depth;    /* current query list index */
    AfterTriggerEventList *query_stack; /* events pending from each query */
    Tuplestorestate **fdw_tuplestores;  /* foreign tuples from each query */
    int         maxquerydepth;  /* allocated len of above array */
    MemoryContext event_cxt;    /* memory context for events, if any */

    /* these fields are just for resetting at subtrans abort: */

    SetConstraintState *state_stack;    /* stacked S C states */
    AfterTriggerEventList *events_stack;        /* stacked list pointers */
    int        *depth_stack;    /* stacked query_depths */
    CommandId  *firing_stack;   /* stacked firing_counters */
    int         maxtransdepth;  /* allocated len of above arrays */
} AfterTriggersData;

static AfterTriggersData afterTriggers;

static void AfterTriggerExecute(AfterTriggerEvent event,
                    Relation rel, TriggerDesc *trigdesc,
                    FmgrInfo *finfo,
                    Instrumentation *instr,
                    MemoryContext per_tuple_context,
                    TupleTableSlot *trig_tuple_slot1,
                    TupleTableSlot *trig_tuple_slot2);
static SetConstraintState SetConstraintStateCreate(int numalloc);
static SetConstraintState SetConstraintStateCopy(SetConstraintState state);
static SetConstraintState SetConstraintStateAddItem(SetConstraintState state,
                          Oid tgoid, bool tgisdeferred);


/*
 * Gets the current query fdw tuplestore and initializes it if necessary
 */
static Tuplestorestate *
GetCurrentFDWTuplestore(void)
{
    Tuplestorestate *ret;

    ret = afterTriggers.fdw_tuplestores[afterTriggers.query_depth];
    if (ret == NULL)
    {
        MemoryContext oldcxt;
        ResourceOwner saveResourceOwner;

        /*
         * Make the tuplestore valid until end of transaction.  This is the
         * allocation lifespan of the associated events list, but we really
         * only need it until AfterTriggerEndQuery().
         */
        oldcxt = MemoryContextSwitchTo(TopTransactionContext);
        saveResourceOwner = CurrentResourceOwner;
        PG_TRY();
        {
            CurrentResourceOwner = TopTransactionResourceOwner;
            ret = tuplestore_begin_heap(false, false, work_mem);
        }
        PG_CATCH();
        {
            CurrentResourceOwner = saveResourceOwner;
            PG_RE_THROW();
        }
        PG_END_TRY();
        CurrentResourceOwner = saveResourceOwner;
        MemoryContextSwitchTo(oldcxt);

        afterTriggers.fdw_tuplestores[afterTriggers.query_depth] = ret;
    }

    return ret;
}

/* ----------
 * afterTriggerCheckState()
 *
 *  Returns true if the trigger event is actually in state DEFERRED.
 * ----------
 */
static bool
afterTriggerCheckState(AfterTriggerShared evtshared)
{
    Oid         tgoid = evtshared->ats_tgoid;
    SetConstraintState state = afterTriggers.state;
    int         i;

    /*
     * For not-deferrable triggers (i.e. normal AFTER ROW triggers and
     * constraints declared NOT DEFERRABLE), the state is always false.
     */
    if ((evtshared->ats_event & AFTER_TRIGGER_DEFERRABLE) == 0)
        return false;

    /*
     * If constraint state exists, SET CONSTRAINTS might have been executed
     * either for this trigger or for all triggers.
     */
    if (state != NULL)
    {
        /* Check for SET CONSTRAINTS for this specific trigger. */
        for (i = 0; i < state->numstates; i++)
        {
            if (state->trigstates[i].sct_tgoid == tgoid)
                return state->trigstates[i].sct_tgisdeferred;
        }

        /* Check for SET CONSTRAINTS ALL. */
        if (state->all_isset)
            return state->all_isdeferred;
    }

    /*
     * Otherwise return the default state for the trigger.
     */
    return ((evtshared->ats_event & AFTER_TRIGGER_INITDEFERRED) != 0);
}


/* ----------
 * afterTriggerAddEvent()
 *
 *  Add a new trigger event to the specified queue.
 *  The passed-in event data is copied.
 * ----------
 */
static void
afterTriggerAddEvent(AfterTriggerEventList *events,
                     AfterTriggerEvent event, AfterTriggerShared evtshared)
{
    Size        eventsize = SizeofTriggerEvent(event);
    Size        needed = eventsize + sizeof(AfterTriggerSharedData);
    AfterTriggerEventChunk *chunk;
    AfterTriggerShared newshared;
    AfterTriggerEvent newevent;

    /*
     * If empty list or not enough room in the tail chunk, make a new chunk.
     * We assume here that a new shared record will always be needed.
     */
    chunk = events->tail;
    if (chunk == NULL ||
        chunk->endfree - chunk->freeptr < needed)
    {
        Size        chunksize;

        /* Create event context if we didn't already */
        if (afterTriggers.event_cxt == NULL)
            afterTriggers.event_cxt =
                AllocSetContextCreate(TopTransactionContext,
                                      "AfterTriggerEvents",
                                      ALLOCSET_DEFAULT_MINSIZE,
                                      ALLOCSET_DEFAULT_INITSIZE,
                                      ALLOCSET_DEFAULT_MAXSIZE);

        /*
         * Chunk size starts at 1KB and is allowed to increase up to 1MB.
         * These numbers are fairly arbitrary, though there is a hard limit at
         * AFTER_TRIGGER_OFFSET; else we couldn't link event records to their
         * shared records using the available space in ate_flags.  Another
         * constraint is that if the chunk size gets too huge, the search loop
         * below would get slow given a (not too common) usage pattern with
         * many distinct event types in a chunk.  Therefore, we double the
         * preceding chunk size only if there weren't too many shared records
         * in the preceding chunk; otherwise we halve it.  This gives us some
         * ability to adapt to the actual usage pattern of the current query
         * while still having large chunk sizes in typical usage.  All chunk
         * sizes used should be MAXALIGN multiples, to ensure that the shared
         * records will be aligned safely.
         */
#define MIN_CHUNK_SIZE 1024
#define MAX_CHUNK_SIZE (1024*1024)

#if MAX_CHUNK_SIZE > (AFTER_TRIGGER_OFFSET+1)
#error MAX_CHUNK_SIZE must not exceed AFTER_TRIGGER_OFFSET
#endif

        if (chunk == NULL)
            chunksize = MIN_CHUNK_SIZE;
        else
        {
            /* preceding chunk size... */
            chunksize = chunk->endptr - (char *) chunk;
            /* check number of shared records in preceding chunk */
            if ((chunk->endptr - chunk->endfree) <=
                (100 * sizeof(AfterTriggerSharedData)))
                chunksize *= 2; /* okay, double it */
            else
                chunksize /= 2; /* too many shared records */
            chunksize = Min(chunksize, MAX_CHUNK_SIZE);
        }
        chunk = MemoryContextAlloc(afterTriggers.event_cxt, chunksize);
        chunk->next = NULL;
        chunk->freeptr = CHUNK_DATA_START(chunk);
        chunk->endptr = chunk->endfree = (char *) chunk + chunksize;
        Assert(chunk->endfree - chunk->freeptr >= needed);

        if (events->head == NULL)
            events->head = chunk;
        else
            events->tail->next = chunk;
        events->tail = chunk;
        /* events->tailfree is now out of sync, but we'll fix it below */
    }

    /*
     * Try to locate a matching shared-data record already in the chunk. If
     * none, make a new one.
     */
    for (newshared = ((AfterTriggerShared) chunk->endptr) - 1;
         (char *) newshared >= chunk->endfree;
         newshared--)
    {
        if (newshared->ats_tgoid == evtshared->ats_tgoid &&
            newshared->ats_relid == evtshared->ats_relid &&
            newshared->ats_event == evtshared->ats_event &&
            newshared->ats_firing_id == 0)
            break;
    }
    if ((char *) newshared < chunk->endfree)
    {
        *newshared = *evtshared;
        newshared->ats_firing_id = 0;   /* just to be sure */
        chunk->endfree = (char *) newshared;
    }

    /* Insert the data */
    newevent = (AfterTriggerEvent) chunk->freeptr;
    memcpy(newevent, event, eventsize);
    /* ... and link the new event to its shared record */
    newevent->ate_flags &= ~AFTER_TRIGGER_OFFSET;
    newevent->ate_flags |= (char *) newshared - (char *) newevent;

    chunk->freeptr += eventsize;
    events->tailfree = chunk->freeptr;
}

/* ----------
 * afterTriggerFreeEventList()
 *
 *  Free all the event storage in the given list.
 * ----------
 */
static void
afterTriggerFreeEventList(AfterTriggerEventList *events)
{
    AfterTriggerEventChunk *chunk;
    AfterTriggerEventChunk *next_chunk;

    for (chunk = events->head; chunk != NULL; chunk = next_chunk)
    {
        next_chunk = chunk->next;
        pfree(chunk);
    }
    events->head = NULL;
    events->tail = NULL;
    events->tailfree = NULL;
}

/* ----------
 * afterTriggerRestoreEventList()
 *
 *  Restore an event list to its prior length, removing all the events
 *  added since it had the value old_events.
 * ----------
 */
static void
afterTriggerRestoreEventList(AfterTriggerEventList *events,
                             const AfterTriggerEventList *old_events)
{
    AfterTriggerEventChunk *chunk;
    AfterTriggerEventChunk *next_chunk;

    if (old_events->tail == NULL)
    {
        /* restoring to a completely empty state, so free everything */
        afterTriggerFreeEventList(events);
    }
    else
    {
        *events = *old_events;
        /* free any chunks after the last one we want to keep */
        for (chunk = events->tail->next; chunk != NULL; chunk = next_chunk)
        {
            next_chunk = chunk->next;
            pfree(chunk);
        }
        /* and clean up the tail chunk to be the right length */
        events->tail->next = NULL;
        events->tail->freeptr = events->tailfree;

        /*
         * We don't make any effort to remove now-unused shared data records.
         * They might still be useful, anyway.
         */
    }
}


/* ----------
 * AfterTriggerExecute()
 *
 *  Fetch the required tuples back from the heap and fire one
 *  single trigger function.
 *
 *  Frequently, this will be fired many times in a row for triggers of
 *  a single relation.  Therefore, we cache the open relation and provide
 *  fmgr lookup cache space at the caller level.  (For triggers fired at
 *  the end of a query, we can even piggyback on the executor's state.)
 *
 *  event: event currently being fired.
 *  rel: open relation for event.
 *  trigdesc: working copy of rel's trigger info.
 *  finfo: array of fmgr lookup cache entries (one per trigger in trigdesc).
 *  instr: array of EXPLAIN ANALYZE instrumentation nodes (one per trigger),
 *      or NULL if no instrumentation is wanted.
 *  per_tuple_context: memory context to call trigger function in.
 *  trig_tuple_slot1: scratch slot for tg_trigtuple (foreign tables only)
 *  trig_tuple_slot2: scratch slot for tg_newtuple (foreign tables only)
 * ----------
 */
static void
AfterTriggerExecute(AfterTriggerEvent event,
                    Relation rel, TriggerDesc *trigdesc,
                    FmgrInfo *finfo, Instrumentation *instr,
                    MemoryContext per_tuple_context,
                    TupleTableSlot *trig_tuple_slot1,
                    TupleTableSlot *trig_tuple_slot2)
{
    AfterTriggerShared evtshared = GetTriggerSharedData(event);
    Oid         tgoid = evtshared->ats_tgoid;
    TriggerData LocTriggerData;
    HeapTupleData tuple1;
    HeapTupleData tuple2;
    HeapTuple   rettuple;
    Buffer      buffer1 = InvalidBuffer;
    Buffer      buffer2 = InvalidBuffer;
    int         tgindx;

    /*
     * Locate trigger in trigdesc.
     */
    LocTriggerData.tg_trigger = NULL;
    for (tgindx = 0; tgindx < trigdesc->numtriggers; tgindx++)
    {
        if (trigdesc->triggers[tgindx].tgoid == tgoid)
        {
            LocTriggerData.tg_trigger = &(trigdesc->triggers[tgindx]);
            break;
        }
    }
    if (LocTriggerData.tg_trigger == NULL)
        elog(ERROR, "could not find trigger %u", tgoid);

    /*
     * If doing EXPLAIN ANALYZE, start charging time to this trigger. We want
     * to include time spent re-fetching tuples in the trigger cost.
     */
    if (instr)
        InstrStartNode(instr + tgindx);

    /*
     * Fetch the required tuple(s).
     */
    switch (event->ate_flags & AFTER_TRIGGER_TUP_BITS)
    {
        case AFTER_TRIGGER_FDW_FETCH:
            {
                Tuplestorestate *fdw_tuplestore = GetCurrentFDWTuplestore();

                if (!tuplestore_gettupleslot(fdw_tuplestore, true, false,
                                             trig_tuple_slot1))
                    elog(ERROR, "failed to fetch tuple1 for AFTER trigger");

                if ((evtshared->ats_event & TRIGGER_EVENT_OPMASK) ==
                    TRIGGER_EVENT_UPDATE &&
                    !tuplestore_gettupleslot(fdw_tuplestore, true, false,
                                             trig_tuple_slot2))
                    elog(ERROR, "failed to fetch tuple2 for AFTER trigger");
            }
            /* fall through */
        case AFTER_TRIGGER_FDW_REUSE:

            /*
             * Using ExecMaterializeSlot() rather than ExecFetchSlotTuple()
             * ensures that tg_trigtuple does not reference tuplestore memory.
             * (It is formally possible for the trigger function to queue
             * trigger events that add to the same tuplestore, which can push
             * other tuples out of memory.)  The distinction is academic,
             * because we start with a minimal tuple that ExecFetchSlotTuple()
             * must materialize anyway.
             */
            LocTriggerData.tg_trigtuple =
                ExecMaterializeSlot(trig_tuple_slot1);
            LocTriggerData.tg_trigtuplebuf = InvalidBuffer;

            LocTriggerData.tg_newtuple =
                ((evtshared->ats_event & TRIGGER_EVENT_OPMASK) ==
                 TRIGGER_EVENT_UPDATE) ?
                ExecMaterializeSlot(trig_tuple_slot2) : NULL;
            LocTriggerData.tg_newtuplebuf = InvalidBuffer;

            break;

        default:
            if (ItemPointerIsValid(&(event->ate_ctid1)))
            {
                ItemPointerCopy(&(event->ate_ctid1), &(tuple1.t_self));
                if (!heap_fetch(rel, SnapshotAny, &tuple1, &buffer1, false, NULL))
                    elog(ERROR, "failed to fetch tuple1 for AFTER trigger");
                LocTriggerData.tg_trigtuple = &tuple1;
                LocTriggerData.tg_trigtuplebuf = buffer1;
            }
            else
            {
                LocTriggerData.tg_trigtuple = NULL;
                LocTriggerData.tg_trigtuplebuf = InvalidBuffer;
            }

            /* don't touch ctid2 if not there */
            if ((event->ate_flags & AFTER_TRIGGER_TUP_BITS) ==
                AFTER_TRIGGER_2CTID &&
                ItemPointerIsValid(&(event->ate_ctid2)))
            {
                ItemPointerCopy(&(event->ate_ctid2), &(tuple2.t_self));
                if (!heap_fetch(rel, SnapshotAny, &tuple2, &buffer2, false, NULL))
                    elog(ERROR, "failed to fetch tuple2 for AFTER trigger");
                LocTriggerData.tg_newtuple = &tuple2;
                LocTriggerData.tg_newtuplebuf = buffer2;
            }
            else
            {
                LocTriggerData.tg_newtuple = NULL;
                LocTriggerData.tg_newtuplebuf = InvalidBuffer;
            }
    }

    /*
     * Setup the remaining trigger information
     */
    LocTriggerData.type = T_TriggerData;
    LocTriggerData.tg_event =
        evtshared->ats_event & (TRIGGER_EVENT_OPMASK | TRIGGER_EVENT_ROW);
    LocTriggerData.tg_relation = rel;

    MemoryContextReset(per_tuple_context);

    /*
     * Call the trigger and throw away any possibly returned updated tuple.
     * (Don't let ExecCallTriggerFunc measure EXPLAIN time.)
     */
    rettuple = ExecCallTriggerFunc(&LocTriggerData,
                                   tgindx,
                                   finfo,
                                   NULL,
                                   per_tuple_context);
    if (rettuple != NULL &&
        rettuple != LocTriggerData.tg_trigtuple &&
        rettuple != LocTriggerData.tg_newtuple)
        heap_freetuple(rettuple);

    /*
     * Release buffers
     */
    if (buffer1 != InvalidBuffer)
        ReleaseBuffer(buffer1);
    if (buffer2 != InvalidBuffer)
        ReleaseBuffer(buffer2);

    /*
     * If doing EXPLAIN ANALYZE, stop charging time to this trigger, and count
     * one "tuple returned" (really the number of firings).
     */
    if (instr)
        InstrStopNode(instr + tgindx, 1);
}


/*
 * afterTriggerMarkEvents()
 *
 *  Scan the given event list for not yet invoked events.  Mark the ones
 *  that can be invoked now with the current firing ID.
 *
 *  If move_list isn't NULL, events that are not to be invoked now are
 *  transferred to move_list.
 *
 *  When immediate_only is TRUE, do not invoke currently-deferred triggers.
 *  (This will be FALSE only at main transaction exit.)
 *
 *  Returns TRUE if any invokable events were found.
 */
static bool
afterTriggerMarkEvents(AfterTriggerEventList *events,
                       AfterTriggerEventList *move_list,
                       bool immediate_only)
{
    bool        found = false;
    AfterTriggerEvent event;
    AfterTriggerEventChunk *chunk;

    for_each_event_chunk(event, chunk, *events)
    {
        AfterTriggerShared evtshared = GetTriggerSharedData(event);
        bool        defer_it = false;

        if (!(event->ate_flags &
              (AFTER_TRIGGER_DONE | AFTER_TRIGGER_IN_PROGRESS)))
        {
            /*
             * This trigger hasn't been called or scheduled yet. Check if we
             * should call it now.
             */
            if (immediate_only && afterTriggerCheckState(evtshared))
            {
                defer_it = true;
            }
            else
            {
                /*
                 * Mark it as to be fired in this firing cycle.
                 */
                evtshared->ats_firing_id = afterTriggers.firing_counter;
                event->ate_flags |= AFTER_TRIGGER_IN_PROGRESS;
                found = true;
            }
        }

        /*
         * If it's deferred, move it to move_list, if requested.
         */
        if (defer_it && move_list != NULL)
        {
            /* add it to move_list */
            afterTriggerAddEvent(move_list, event, evtshared);
            /* mark original copy "done" so we don't do it again */
            event->ate_flags |= AFTER_TRIGGER_DONE;
        }
    }

    return found;
}

/*
 * afterTriggerInvokeEvents()
 *
 *  Scan the given event list for events that are marked as to be fired
 *  in the current firing cycle, and fire them.
 *
 *  If estate isn't NULL, we use its result relation info to avoid repeated
 *  openings and closing of trigger target relations.  If it is NULL, we
 *  make one locally to cache the info in case there are multiple trigger
 *  events per rel.
 *
 *  When delete_ok is TRUE, it's safe to delete fully-processed events.
 *  (We are not very tense about that: we simply reset a chunk to be empty
 *  if all its events got fired.  The objective here is just to avoid useless
 *  rescanning of events when a trigger queues new events during transaction
 *  end, so it's not necessary to worry much about the case where only
 *  some events are fired.)
 *
 *  Returns TRUE if no unfired events remain in the list (this allows us
 *  to avoid repeating afterTriggerMarkEvents).
 */
static bool
afterTriggerInvokeEvents(AfterTriggerEventList *events,
                         CommandId firing_id,
                         EState *estate,
                         bool delete_ok)
{
    bool        all_fired = true;
    AfterTriggerEventChunk *chunk;
    MemoryContext per_tuple_context;
    bool        local_estate = false;
    Relation    rel = NULL;
    TriggerDesc *trigdesc = NULL;
    FmgrInfo   *finfo = NULL;
    Instrumentation *instr = NULL;
    TupleTableSlot *slot1 = NULL,
               *slot2 = NULL;

    /* Make a local EState if need be */
    if (estate == NULL)
    {
        estate = CreateExecutorState();
        local_estate = true;
    }

    /* Make a per-tuple memory context for trigger function calls */
    per_tuple_context =
        AllocSetContextCreate(CurrentMemoryContext,
                              "AfterTriggerTupleContext",
                              ALLOCSET_DEFAULT_MINSIZE,
                              ALLOCSET_DEFAULT_INITSIZE,
                              ALLOCSET_DEFAULT_MAXSIZE);

    for_each_chunk(chunk, *events)
    {
        AfterTriggerEvent event;
        bool        all_fired_in_chunk = true;

        for_each_event(event, chunk)
        {
            AfterTriggerShared evtshared = GetTriggerSharedData(event);

            /*
             * Is it one for me to fire?
             */
            if ((event->ate_flags & AFTER_TRIGGER_IN_PROGRESS) &&
                evtshared->ats_firing_id == firing_id)
            {
                /*
                 * So let's fire it... but first, find the correct relation if
                 * this is not the same relation as before.
                 */
                if (rel == NULL || RelationGetRelid(rel) != evtshared->ats_relid)
                {
                    ResultRelInfo *rInfo;

                    rInfo = ExecGetTriggerResultRel(estate, evtshared->ats_relid);
                    rel = rInfo->ri_RelationDesc;
                    trigdesc = rInfo->ri_TrigDesc;
                    finfo = rInfo->ri_TrigFunctions;
                    instr = rInfo->ri_TrigInstrument;
                    if (rel->rd_rel->relkind == RELKIND_FOREIGN_TABLE)
                    {
                        if (slot1 != NULL)
                        {
                            ExecDropSingleTupleTableSlot(slot1);
                            ExecDropSingleTupleTableSlot(slot2);
                        }
                        slot1 = MakeSingleTupleTableSlot(rel->rd_att);
                        slot2 = MakeSingleTupleTableSlot(rel->rd_att);
                    }
                    if (trigdesc == NULL)       /* should not happen */
                        elog(ERROR, "relation %u has no triggers",
                             evtshared->ats_relid);
                }

                /*
                 * Fire it.  Note that the AFTER_TRIGGER_IN_PROGRESS flag is
                 * still set, so recursive examinations of the event list
                 * won't try to re-fire it.
                 */
                AfterTriggerExecute(event, rel, trigdesc, finfo, instr,
                                    per_tuple_context, slot1, slot2);

                /*
                 * Mark the event as done.
                 */
                event->ate_flags &= ~AFTER_TRIGGER_IN_PROGRESS;
                event->ate_flags |= AFTER_TRIGGER_DONE;
            }
            else if (!(event->ate_flags & AFTER_TRIGGER_DONE))
            {
                /* something remains to be done */
                all_fired = all_fired_in_chunk = false;
            }
        }

        /* Clear the chunk if delete_ok and nothing left of interest */
        if (delete_ok && all_fired_in_chunk)
        {
            chunk->freeptr = CHUNK_DATA_START(chunk);
            chunk->endfree = chunk->endptr;

            /*
             * If it's last chunk, must sync event list's tailfree too.  Note
             * that delete_ok must NOT be passed as true if there could be
             * stacked AfterTriggerEventList values pointing at this event
             * list, since we'd fail to fix their copies of tailfree.
             */
            if (chunk == events->tail)
                events->tailfree = chunk->freeptr;
        }
    }
    if (slot1 != NULL)
    {
        ExecDropSingleTupleTableSlot(slot1);
        ExecDropSingleTupleTableSlot(slot2);
    }

    /* Release working resources */
    MemoryContextDelete(per_tuple_context);

    if (local_estate)
    {
        ListCell   *l;

        foreach(l, estate->es_trig_target_relations)
        {
            ResultRelInfo *resultRelInfo = (ResultRelInfo *) lfirst(l);

            /* Close indices and then the relation itself */
            ExecCloseIndices(resultRelInfo);
            heap_close(resultRelInfo->ri_RelationDesc, NoLock);
        }
        FreeExecutorState(estate);
    }

    return all_fired;
}


/* ----------
 * AfterTriggerBeginXact()
 *
 *  Called at transaction start (either BEGIN or implicit for single
 *  statement outside of transaction block).
 * ----------
 */
void
AfterTriggerBeginXact(void)
{
    /*
     * Initialize after-trigger state structure to empty
     */
    afterTriggers.firing_counter = (CommandId) 1;       /* mustn't be 0 */
    afterTriggers.query_depth = -1;

    /*
     * Verify that there is no leftover state remaining.  If these assertions
     * trip, it means that AfterTriggerEndXact wasn't called or didn't clean
     * up properly.
     */
    Assert(afterTriggers.state == NULL);
    Assert(afterTriggers.query_stack == NULL);
    Assert(afterTriggers.fdw_tuplestores == NULL);
    Assert(afterTriggers.maxquerydepth == 0);
    Assert(afterTriggers.event_cxt == NULL);
    Assert(afterTriggers.events.head == NULL);
    Assert(afterTriggers.state_stack == NULL);
    Assert(afterTriggers.events_stack == NULL);
    Assert(afterTriggers.depth_stack == NULL);
    Assert(afterTriggers.firing_stack == NULL);
    Assert(afterTriggers.maxtransdepth == 0);
}


/* ----------
 * AfterTriggerBeginQuery()
 *
 *  Called just before we start processing a single query within a
 *  transaction (or subtransaction).  Most of the real work gets deferred
 *  until somebody actually tries to queue a trigger event.
 * ----------
 */
void
AfterTriggerBeginQuery(void)
{
    /* Increase the query stack depth */
    afterTriggers.query_depth++;
}


/* ----------
 * AfterTriggerEndQuery()
 *
 *  Called after one query has been completely processed. At this time
 *  we invoke all AFTER IMMEDIATE trigger events queued by the query, and
 *  transfer deferred trigger events to the global deferred-trigger list.
 *
 *  Note that this must be called BEFORE closing down the executor
 *  with ExecutorEnd, because we make use of the EState's info about
 *  target relations.  Normally it is called from ExecutorFinish.
 * ----------
 */
void
AfterTriggerEndQuery(EState *estate)
{
    AfterTriggerEventList *events;
    Tuplestorestate *fdw_tuplestore;

    /* Must be inside a query, too */
    Assert(afterTriggers.query_depth >= 0);

    /*
     * If we never even got as far as initializing the event stack, there
     * certainly won't be any events, so exit quickly.
     */
    if (afterTriggers.query_depth >= afterTriggers.maxquerydepth)
    {
        afterTriggers.query_depth--;
        return;
    }

    /*
     * Process all immediate-mode triggers queued by the query, and move the
     * deferred ones to the main list of deferred events.
     *
     * Notice that we decide which ones will be fired, and put the deferred
     * ones on the main list, before anything is actually fired.  This ensures
     * reasonably sane behavior if a trigger function does SET CONSTRAINTS ...
     * IMMEDIATE: all events we have decided to defer will be available for it
     * to fire.
     *
     * We loop in case a trigger queues more events at the same query level.
     * Ordinary trigger functions, including all PL/pgSQL trigger functions,
     * will instead fire any triggers in a dedicated query level.  Foreign key
     * enforcement triggers do add to the current query level, thanks to their
     * passing fire_triggers = false to SPI_execute_snapshot().  Other
     * C-language triggers might do likewise.  Be careful here: firing a
     * trigger could result in query_stack being repalloc'd, so we can't save
     * its address across afterTriggerInvokeEvents calls.
     *
     * If we find no firable events, we don't have to increment
     * firing_counter.
     */
    for (;;)
    {
        events = &afterTriggers.query_stack[afterTriggers.query_depth];
        if (afterTriggerMarkEvents(events, &afterTriggers.events, true))
        {
            CommandId   firing_id = afterTriggers.firing_counter++;

            /* OK to delete the immediate events after processing them */
            if (afterTriggerInvokeEvents(events, firing_id, estate, true))
                break;          /* all fired */
        }
        else
            break;
    }

    /* Release query-local storage for events, including tuplestore if any */
    fdw_tuplestore = afterTriggers.fdw_tuplestores[afterTriggers.query_depth];
    if (fdw_tuplestore)
    {
        tuplestore_end(fdw_tuplestore);
        afterTriggers.fdw_tuplestores[afterTriggers.query_depth] = NULL;
    }
    afterTriggerFreeEventList(&afterTriggers.query_stack[afterTriggers.query_depth]);

    afterTriggers.query_depth--;
}


/* ----------
 * AfterTriggerFireDeferred()
 *
 *  Called just before the current transaction is committed. At this
 *  time we invoke all pending DEFERRED triggers.
 *
 *  It is possible for other modules to queue additional deferred triggers
 *  during pre-commit processing; therefore xact.c may have to call this
 *  multiple times.
 * ----------
 */
void
AfterTriggerFireDeferred(void)
{
    AfterTriggerEventList *events;
    bool        snap_pushed = false;

    /* Must not be inside a query */
    Assert(afterTriggers.query_depth == -1);

    /*
     * If there are any triggers to fire, make sure we have set a snapshot for
     * them to use.  (Since PortalRunUtility doesn't set a snap for COMMIT, we
     * can't assume ActiveSnapshot is valid on entry.)
     */
    events = &afterTriggers.events;
    if (events->head != NULL)
    {
        PushActiveSnapshot(GetTransactionSnapshot());
        snap_pushed = true;
    }

    /*
     * Run all the remaining triggers.  Loop until they are all gone, in case
     * some trigger queues more for us to do.
     */
    while (afterTriggerMarkEvents(events, NULL, false))
    {
        CommandId   firing_id = afterTriggers.firing_counter++;

        if (afterTriggerInvokeEvents(events, firing_id, NULL, true))
            break;              /* all fired */
    }

    /*
     * We don't bother freeing the event list, since it will go away anyway
     * (and more efficiently than via pfree) in AfterTriggerEndXact.
     */

    if (snap_pushed)
        PopActiveSnapshot();
}


/* ----------
 * AfterTriggerEndXact()
 *
 *  The current transaction is finishing.
 *
 *  Any unfired triggers are canceled so we simply throw
 *  away anything we know.
 *
 *  Note: it is possible for this to be called repeatedly in case of
 *  error during transaction abort; therefore, do not complain if
 *  already closed down.
 * ----------
 */
void
AfterTriggerEndXact(bool isCommit)
{
    /*
     * Forget the pending-events list.
     *
     * Since all the info is in TopTransactionContext or children thereof, we
     * don't really need to do anything to reclaim memory.  However, the
     * pending-events list could be large, and so it's useful to discard it as
     * soon as possible --- especially if we are aborting because we ran out
     * of memory for the list!
     */
    if (afterTriggers.event_cxt)
    {
        MemoryContextDelete(afterTriggers.event_cxt);
        afterTriggers.event_cxt = NULL;
        afterTriggers.events.head = NULL;
        afterTriggers.events.tail = NULL;
        afterTriggers.events.tailfree = NULL;
    }

    /*
     * Forget any subtransaction state as well.  Since this can't be very
     * large, we let the eventual reset of TopTransactionContext free the
     * memory instead of doing it here.
     */
    afterTriggers.state_stack = NULL;
    afterTriggers.events_stack = NULL;
    afterTriggers.depth_stack = NULL;
    afterTriggers.firing_stack = NULL;
    afterTriggers.maxtransdepth = 0;


    /*
     * Forget the query stack and constraint-related state information.  As
     * with the subtransaction state information, we don't bother freeing the
     * memory here.
     */
    afterTriggers.query_stack = NULL;
    afterTriggers.fdw_tuplestores = NULL;
    afterTriggers.maxquerydepth = 0;
    afterTriggers.state = NULL;

    /* No more afterTriggers manipulation until next transaction starts. */
    afterTriggers.query_depth = -1;
}

/*
 * AfterTriggerBeginSubXact()
 *
 *  Start a subtransaction.
 */
void
AfterTriggerBeginSubXact(void)
{
    int         my_level = GetCurrentTransactionNestLevel();

    /*
     * Allocate more space in the stacks if needed.  (Note: because the
     * minimum nest level of a subtransaction is 2, we waste the first couple
     * entries of each array; not worth the notational effort to avoid it.)
     */
    while (my_level >= afterTriggers.maxtransdepth)
    {
        if (afterTriggers.maxtransdepth == 0)
        {
            MemoryContext old_cxt;

            old_cxt = MemoryContextSwitchTo(TopTransactionContext);

#define DEFTRIG_INITALLOC 8
            afterTriggers.state_stack = (SetConstraintState *)
                palloc(DEFTRIG_INITALLOC * sizeof(SetConstraintState));
            afterTriggers.events_stack = (AfterTriggerEventList *)
                palloc(DEFTRIG_INITALLOC * sizeof(AfterTriggerEventList));
            afterTriggers.depth_stack = (int *)
                palloc(DEFTRIG_INITALLOC * sizeof(int));
            afterTriggers.firing_stack = (CommandId *)
                palloc(DEFTRIG_INITALLOC * sizeof(CommandId));
            afterTriggers.maxtransdepth = DEFTRIG_INITALLOC;

            MemoryContextSwitchTo(old_cxt);
        }
        else
        {
            /* repalloc will keep the stacks in the same context */
            int         new_alloc = afterTriggers.maxtransdepth * 2;

            afterTriggers.state_stack = (SetConstraintState *)
                repalloc(afterTriggers.state_stack,
                         new_alloc * sizeof(SetConstraintState));
            afterTriggers.events_stack = (AfterTriggerEventList *)
                repalloc(afterTriggers.events_stack,
                         new_alloc * sizeof(AfterTriggerEventList));
            afterTriggers.depth_stack = (int *)
                repalloc(afterTriggers.depth_stack,
                         new_alloc * sizeof(int));
            afterTriggers.firing_stack = (CommandId *)
                repalloc(afterTriggers.firing_stack,
                         new_alloc * sizeof(CommandId));
            afterTriggers.maxtransdepth = new_alloc;
        }
    }

    /*
     * Push the current information into the stack.  The SET CONSTRAINTS state
     * is not saved until/unless changed.  Likewise, we don't make a
     * per-subtransaction event context until needed.
     */
    afterTriggers.state_stack[my_level] = NULL;
    afterTriggers.events_stack[my_level] = afterTriggers.events;
    afterTriggers.depth_stack[my_level] = afterTriggers.query_depth;
    afterTriggers.firing_stack[my_level] = afterTriggers.firing_counter;
}

/*
 * AfterTriggerEndSubXact()
 *
 *  The current subtransaction is ending.
 */
void
AfterTriggerEndSubXact(bool isCommit)
{
    int         my_level = GetCurrentTransactionNestLevel();
    SetConstraintState state;
    AfterTriggerEvent event;
    AfterTriggerEventChunk *chunk;
    CommandId   subxact_firing_id;

    /*
     * Pop the prior state if needed.
     */
    if (isCommit)
    {
        Assert(my_level < afterTriggers.maxtransdepth);
        /* If we saved a prior state, we don't need it anymore */
        state = afterTriggers.state_stack[my_level];
        if (state != NULL)
            pfree(state);
        /* this avoids double pfree if error later: */
        afterTriggers.state_stack[my_level] = NULL;
        Assert(afterTriggers.query_depth ==
               afterTriggers.depth_stack[my_level]);
    }
    else
    {
        /*
         * Aborting.  It is possible subxact start failed before calling
         * AfterTriggerBeginSubXact, in which case we mustn't risk touching
         * stack levels that aren't there.
         */
        if (my_level >= afterTriggers.maxtransdepth)
            return;

        /*
         * Release any event lists from queries being aborted, and restore
         * query_depth to its pre-subxact value.  This assumes that a
         * subtransaction will not add events to query levels started in a
         * earlier transaction state.
         */
        while (afterTriggers.query_depth > afterTriggers.depth_stack[my_level])
        {
            if (afterTriggers.query_depth < afterTriggers.maxquerydepth)
            {
                Tuplestorestate *ts;

                ts = afterTriggers.fdw_tuplestores[afterTriggers.query_depth];
                if (ts)
                {
                    tuplestore_end(ts);
                    afterTriggers.fdw_tuplestores[afterTriggers.query_depth] = NULL;
                }

                afterTriggerFreeEventList(&afterTriggers.query_stack[afterTriggers.query_depth]);
            }

            afterTriggers.query_depth--;
        }
        Assert(afterTriggers.query_depth ==
               afterTriggers.depth_stack[my_level]);

        /*
         * Restore the global deferred-event list to its former length,
         * discarding any events queued by the subxact.
         */
        afterTriggerRestoreEventList(&afterTriggers.events,
                                     &afterTriggers.events_stack[my_level]);

        /*
         * Restore the trigger state.  If the saved state is NULL, then this
         * subxact didn't save it, so it doesn't need restoring.
         */
        state = afterTriggers.state_stack[my_level];
        if (state != NULL)
        {
            pfree(afterTriggers.state);
            afterTriggers.state = state;
        }
        /* this avoids double pfree if error later: */
        afterTriggers.state_stack[my_level] = NULL;

        /*
         * Scan for any remaining deferred events that were marked DONE or IN
         * PROGRESS by this subxact or a child, and un-mark them. We can
         * recognize such events because they have a firing ID greater than or
         * equal to the firing_counter value we saved at subtransaction start.
         * (This essentially assumes that the current subxact includes all
         * subxacts started after it.)
         */
        subxact_firing_id = afterTriggers.firing_stack[my_level];
        for_each_event_chunk(event, chunk, afterTriggers.events)
        {
            AfterTriggerShared evtshared = GetTriggerSharedData(event);

            if (event->ate_flags &
                (AFTER_TRIGGER_DONE | AFTER_TRIGGER_IN_PROGRESS))
            {
                if (evtshared->ats_firing_id >= subxact_firing_id)
                    event->ate_flags &=
                        ~(AFTER_TRIGGER_DONE | AFTER_TRIGGER_IN_PROGRESS);
            }
        }
    }
}

/* ----------
 * AfterTriggerEnlargeQueryState()
 *
 *  Prepare the necessary state so that we can record AFTER trigger events
 *  queued by a query.  It is allowed to have nested queries within a
 *  (sub)transaction, so we need to have separate state for each query
 *  nesting level.
 * ----------
 */
static void
AfterTriggerEnlargeQueryState(void)
{
    int         init_depth = afterTriggers.maxquerydepth;

    Assert(afterTriggers.query_depth >= afterTriggers.maxquerydepth);

    if (afterTriggers.maxquerydepth == 0)
    {
        int         new_alloc = Max(afterTriggers.query_depth + 1, 8);

        afterTriggers.query_stack = (AfterTriggerEventList *)
            MemoryContextAlloc(TopTransactionContext,
                               new_alloc * sizeof(AfterTriggerEventList));
        afterTriggers.fdw_tuplestores = (Tuplestorestate **)
            MemoryContextAllocZero(TopTransactionContext,
                                   new_alloc * sizeof(Tuplestorestate *));
        afterTriggers.maxquerydepth = new_alloc;
    }
    else
    {
        /* repalloc will keep the stack in the same context */
        int         old_alloc = afterTriggers.maxquerydepth;
        int         new_alloc = Max(afterTriggers.query_depth + 1,
                                    old_alloc * 2);

        afterTriggers.query_stack = (AfterTriggerEventList *)
            repalloc(afterTriggers.query_stack,
                     new_alloc * sizeof(AfterTriggerEventList));
        afterTriggers.fdw_tuplestores = (Tuplestorestate **)
            repalloc(afterTriggers.fdw_tuplestores,
                     new_alloc * sizeof(Tuplestorestate *));
        /* Clear newly-allocated slots for subsequent lazy initialization. */
        memset(afterTriggers.fdw_tuplestores + old_alloc,
               0, (new_alloc - old_alloc) * sizeof(Tuplestorestate *));
        afterTriggers.maxquerydepth = new_alloc;
    }

    /* Initialize new query lists to empty */
    while (init_depth < afterTriggers.maxquerydepth)
    {
        AfterTriggerEventList *events;

        events = &afterTriggers.query_stack[init_depth];
        events->head = NULL;
        events->tail = NULL;
        events->tailfree = NULL;

        ++init_depth;
    }
}

/*
 * Create an empty SetConstraintState with room for numalloc trigstates
 */
static SetConstraintState
SetConstraintStateCreate(int numalloc)
{
    SetConstraintState state;

    /* Behave sanely with numalloc == 0 */
    if (numalloc <= 0)
        numalloc = 1;

    /*
     * We assume that zeroing will correctly initialize the state values.
     */
    state = (SetConstraintState)
        MemoryContextAllocZero(TopTransactionContext,
                               offsetof(SetConstraintStateData, trigstates) +
                               numalloc * sizeof(SetConstraintTriggerData));

    state->numalloc = numalloc;

    return state;
}

/*
 * Copy a SetConstraintState
 */
static SetConstraintState
SetConstraintStateCopy(SetConstraintState origstate)
{
    SetConstraintState state;

    state = SetConstraintStateCreate(origstate->numstates);

    state->all_isset = origstate->all_isset;
    state->all_isdeferred = origstate->all_isdeferred;
    state->numstates = origstate->numstates;
    memcpy(state->trigstates, origstate->trigstates,
           origstate->numstates * sizeof(SetConstraintTriggerData));

    return state;
}

/*
 * Add a per-trigger item to a SetConstraintState.  Returns possibly-changed
 * pointer to the state object (it will change if we have to repalloc).
 */
static SetConstraintState
SetConstraintStateAddItem(SetConstraintState state,
                          Oid tgoid, bool tgisdeferred)
{
    if (state->numstates >= state->numalloc)
    {
        int         newalloc = state->numalloc * 2;

        newalloc = Max(newalloc, 8);    /* in case original has size 0 */
        state = (SetConstraintState)
            repalloc(state,
                     offsetof(SetConstraintStateData, trigstates) +
                     newalloc * sizeof(SetConstraintTriggerData));
        state->numalloc = newalloc;
        Assert(state->numstates < state->numalloc);
    }

    state->trigstates[state->numstates].sct_tgoid = tgoid;
    state->trigstates[state->numstates].sct_tgisdeferred = tgisdeferred;
    state->numstates++;

    return state;
}

/* ----------
 * AfterTriggerSetState()
 *
 *  Execute the SET CONSTRAINTS ... utility command.
 * ----------
 */
void
AfterTriggerSetState(ConstraintsSetStmt *stmt)
{
    int         my_level = GetCurrentTransactionNestLevel();

    /* If we haven't already done so, initialize our state. */
    if (afterTriggers.state == NULL)
        afterTriggers.state = SetConstraintStateCreate(8);

    /*
     * If in a subtransaction, and we didn't save the current state already,
     * save it so it can be restored if the subtransaction aborts.
     */
    if (my_level > 1 &&
        afterTriggers.state_stack[my_level] == NULL)
    {
        afterTriggers.state_stack[my_level] =
            SetConstraintStateCopy(afterTriggers.state);
    }

    /*
     * Handle SET CONSTRAINTS ALL ...
     */
    if (stmt->constraints == NIL)
    {
        /*
         * Forget any previous SET CONSTRAINTS commands in this transaction.
         */
        afterTriggers.state->numstates = 0;

        /*
         * Set the per-transaction ALL state to known.
         */
        afterTriggers.state->all_isset = true;
        afterTriggers.state->all_isdeferred = stmt->deferred;
    }
    else
    {
        Relation    conrel;
        Relation    tgrel;
        List       *conoidlist = NIL;
        List       *tgoidlist = NIL;
        ListCell   *lc;

        /*
         * Handle SET CONSTRAINTS constraint-name [, ...]
         *
         * First, identify all the named constraints and make a list of their
         * OIDs.  Since, unlike the SQL spec, we allow multiple constraints of
         * the same name within a schema, the specifications are not
         * necessarily unique.  Our strategy is to target all matching
         * constraints within the first search-path schema that has any
         * matches, but disregard matches in schemas beyond the first match.
         * (This is a bit odd but it's the historical behavior.)
         */
        conrel = heap_open(ConstraintRelationId, AccessShareLock);

        foreach(lc, stmt->constraints)
        {
            RangeVar   *constraint = lfirst(lc);
            bool        found;
            List       *namespacelist;
            ListCell   *nslc;

            if (constraint->catalogname)
            {
                if (strcmp(constraint->catalogname, get_database_name(MyDatabaseId)) != 0)
                    ereport(ERROR,
                            (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                             errmsg("cross-database references are not implemented: \"%s.%s.%s\"",
                             constraint->catalogname, constraint->schemaname,
                                    constraint->relname)));
            }

            /*
             * If we're given the schema name with the constraint, look only
             * in that schema.  If given a bare constraint name, use the
             * search path to find the first matching constraint.
             */
            if (constraint->schemaname)
            {
                Oid         namespaceId = LookupExplicitNamespace(constraint->schemaname,
                                                                  false);

                namespacelist = list_make1_oid(namespaceId);
            }
            else
            {
                namespacelist = fetch_search_path(true);
            }

            found = false;
            foreach(nslc, namespacelist)
            {
                Oid         namespaceId = lfirst_oid(nslc);
                SysScanDesc conscan;
                ScanKeyData skey[2];
                HeapTuple   tup;

                ScanKeyInit(&skey[0],
                            Anum_pg_constraint_conname,
                            BTEqualStrategyNumber, F_NAMEEQ,
                            CStringGetDatum(constraint->relname));
                ScanKeyInit(&skey[1],
                            Anum_pg_constraint_connamespace,
                            BTEqualStrategyNumber, F_OIDEQ,
                            ObjectIdGetDatum(namespaceId));

                conscan = systable_beginscan(conrel, ConstraintNameNspIndexId,
                                             true, NULL, 2, skey);

                while (HeapTupleIsValid(tup = systable_getnext(conscan)))
                {
                    Form_pg_constraint con = (Form_pg_constraint) GETSTRUCT(tup);

                    if (con->condeferrable)
                        conoidlist = lappend_oid(conoidlist,
                                                 HeapTupleGetOid(tup));
                    else if (stmt->deferred)
                        ereport(ERROR,
                                (errcode(ERRCODE_WRONG_OBJECT_TYPE),
                                 errmsg("constraint \"%s\" is not deferrable",
                                        constraint->relname)));
                    found = true;
                }

                systable_endscan(conscan);

                /*
                 * Once we've found a matching constraint we do not search
                 * later parts of the search path.
                 */
                if (found)
                    break;
            }

            list_free(namespacelist);

            /*
             * Not found ?
             */
            if (!found)
                ereport(ERROR,
                        (errcode(ERRCODE_UNDEFINED_OBJECT),
                         errmsg("constraint \"%s\" does not exist",
                                constraint->relname)));
        }

        heap_close(conrel, AccessShareLock);

        /*
         * Now, locate the trigger(s) implementing each of these constraints,
         * and make a list of their OIDs.
         */
        tgrel = heap_open(TriggerRelationId, AccessShareLock);

        foreach(lc, conoidlist)
        {
            Oid         conoid = lfirst_oid(lc);
            bool        found;
            ScanKeyData skey;
            SysScanDesc tgscan;
            HeapTuple   htup;

            found = false;

            ScanKeyInit(&skey,
                        Anum_pg_trigger_tgconstraint,
                        BTEqualStrategyNumber, F_OIDEQ,
                        ObjectIdGetDatum(conoid));

            tgscan = systable_beginscan(tgrel, TriggerConstraintIndexId, true,
                                        NULL, 1, &skey);

            while (HeapTupleIsValid(htup = systable_getnext(tgscan)))
            {
                Form_pg_trigger pg_trigger = (Form_pg_trigger) GETSTRUCT(htup);

                /*
                 * Silently skip triggers that are marked as non-deferrable in
                 * pg_trigger.  This is not an error condition, since a
                 * deferrable RI constraint may have some non-deferrable
                 * actions.
                 */
                if (pg_trigger->tgdeferrable)
                    tgoidlist = lappend_oid(tgoidlist,
                                            HeapTupleGetOid(htup));

                found = true;
            }

            systable_endscan(tgscan);

            /* Safety check: a deferrable constraint should have triggers */
            if (!found)
                elog(ERROR, "no triggers found for constraint with OID %u",
                     conoid);
        }

        heap_close(tgrel, AccessShareLock);

        /*
         * Now we can set the trigger states of individual triggers for this
         * xact.
         */
        foreach(lc, tgoidlist)
        {
            Oid         tgoid = lfirst_oid(lc);
            SetConstraintState state = afterTriggers.state;
            bool        found = false;
            int         i;

            for (i = 0; i < state->numstates; i++)
            {
                if (state->trigstates[i].sct_tgoid == tgoid)
                {
                    state->trigstates[i].sct_tgisdeferred = stmt->deferred;
                    found = true;
                    break;
                }
            }
            if (!found)
            {
                afterTriggers.state =
                    SetConstraintStateAddItem(state, tgoid, stmt->deferred);
            }
        }
    }

    /*
     * SQL99 requires that when a constraint is set to IMMEDIATE, any deferred
     * checks against that constraint must be made when the SET CONSTRAINTS
     * command is executed -- i.e. the effects of the SET CONSTRAINTS command
     * apply retroactively.  We've updated the constraints state, so scan the
     * list of previously deferred events to fire any that have now become
     * immediate.
     *
     * Obviously, if this was SET ... DEFERRED then it can't have converted
     * any unfired events to immediate, so we need do nothing in that case.
     */
    if (!stmt->deferred)
    {
        AfterTriggerEventList *events = &afterTriggers.events;
        bool        snapshot_set = false;

        while (afterTriggerMarkEvents(events, NULL, true))
        {
            CommandId   firing_id = afterTriggers.firing_counter++;

            /*
             * Make sure a snapshot has been established in case trigger
             * functions need one.  Note that we avoid setting a snapshot if
             * we don't find at least one trigger that has to be fired now.
             * This is so that BEGIN; SET CONSTRAINTS ...; SET TRANSACTION
             * ISOLATION LEVEL SERIALIZABLE; ... works properly.  (If we are
             * at the start of a transaction it's not possible for any trigger
             * events to be queued yet.)
             */
            if (!snapshot_set)
            {
                PushActiveSnapshot(GetTransactionSnapshot());
                snapshot_set = true;
            }

            /*
             * We can delete fired events if we are at top transaction level,
             * but we'd better not if inside a subtransaction, since the
             * subtransaction could later get rolled back.
             */
            if (afterTriggerInvokeEvents(events, firing_id, NULL,
                                         !IsSubTransaction()))
                break;          /* all fired */
        }

        if (snapshot_set)
            PopActiveSnapshot();
    }
}

/* ----------
 * AfterTriggerPendingOnRel()
 *      Test to see if there are any pending after-trigger events for rel.
 *
 * This is used by TRUNCATE, CLUSTER, ALTER TABLE, etc to detect whether
 * it is unsafe to perform major surgery on a relation.  Note that only
 * local pending events are examined.  We assume that having exclusive lock
 * on a rel guarantees there are no unserviced events in other backends ---
 * but having a lock does not prevent there being such events in our own.
 *
 * In some scenarios it'd be reasonable to remove pending events (more
 * specifically, mark them DONE by the current subxact) but without a lot
 * of knowledge of the trigger semantics we can't do this in general.
 * ----------
 */
bool
AfterTriggerPendingOnRel(Oid relid)
{
    AfterTriggerEvent event;
    AfterTriggerEventChunk *chunk;
    int         depth;

    /* Scan queued events */
    for_each_event_chunk(event, chunk, afterTriggers.events)
    {
        AfterTriggerShared evtshared = GetTriggerSharedData(event);

        /*
         * We can ignore completed events.  (Even if a DONE flag is rolled
         * back by subxact abort, it's OK because the effects of the TRUNCATE
         * or whatever must get rolled back too.)
         */
        if (event->ate_flags & AFTER_TRIGGER_DONE)
            continue;

        if (evtshared->ats_relid == relid)
            return true;
    }

    /*
     * Also scan events queued by incomplete queries.  This could only matter
     * if TRUNCATE/etc is executed by a function or trigger within an updating
     * query on the same relation, which is pretty perverse, but let's check.
     */
    for (depth = 0; depth <= afterTriggers.query_depth && depth < afterTriggers.maxquerydepth; depth++)
    {
        for_each_event_chunk(event, chunk, afterTriggers.query_stack[depth])
        {
            AfterTriggerShared evtshared = GetTriggerSharedData(event);

            if (event->ate_flags & AFTER_TRIGGER_DONE)
                continue;

            if (evtshared->ats_relid == relid)
                return true;
        }
    }

    return false;
}


/* ----------
 * AfterTriggerSaveEvent()
 *
 *  Called by ExecA[RS]...Triggers() to queue up the triggers that should
 *  be fired for an event.
 *
 *  NOTE: this is called whenever there are any triggers associated with
 *  the event (even if they are disabled).  This function decides which
 *  triggers actually need to be queued.
 * ----------
 */
static void
AfterTriggerSaveEvent(EState *estate, ResultRelInfo *relinfo,
                      int event, bool row_trigger,
                      HeapTuple oldtup, HeapTuple newtup,
                      List *recheckIndexes, Bitmapset *modifiedCols)
{
    Relation    rel = relinfo->ri_RelationDesc;
    TriggerDesc *trigdesc = relinfo->ri_TrigDesc;
    AfterTriggerEventData new_event;
    AfterTriggerSharedData new_shared;
    char        relkind = relinfo->ri_RelationDesc->rd_rel->relkind;
    int         tgtype_event;
    int         tgtype_level;
    int         i;
    Tuplestorestate *fdw_tuplestore = NULL;

    /*
     * Check state.  We use a normal test not Assert because it is possible to
     * reach here in the wrong state given misconfigured RI triggers, in
     * particular deferring a cascade action trigger.
     */
    if (afterTriggers.query_depth < 0)
        elog(ERROR, "AfterTriggerSaveEvent() called outside of query");

    /* Be sure we have enough space to record events at this query depth. */
    if (afterTriggers.query_depth >= afterTriggers.maxquerydepth)
        AfterTriggerEnlargeQueryState();

    /*
     * Validate the event code and collect the associated tuple CTIDs.
     *
     * The event code will be used both as a bitmask and an array offset, so
     * validation is important to make sure we don't walk off the edge of our
     * arrays.
     */
    switch (event)
    {
        case TRIGGER_EVENT_INSERT:
            tgtype_event = TRIGGER_TYPE_INSERT;
            if (row_trigger)
            {
                Assert(oldtup == NULL);
                Assert(newtup != NULL);
                ItemPointerCopy(&(newtup->t_self), &(new_event.ate_ctid1));
                ItemPointerSetInvalid(&(new_event.ate_ctid2));
            }
            else
            {
                Assert(oldtup == NULL);
                Assert(newtup == NULL);
                ItemPointerSetInvalid(&(new_event.ate_ctid1));
                ItemPointerSetInvalid(&(new_event.ate_ctid2));
            }
            break;
        case TRIGGER_EVENT_DELETE:
            tgtype_event = TRIGGER_TYPE_DELETE;
            if (row_trigger)
            {
                Assert(oldtup != NULL);
                Assert(newtup == NULL);
                ItemPointerCopy(&(oldtup->t_self), &(new_event.ate_ctid1));
                ItemPointerSetInvalid(&(new_event.ate_ctid2));
            }
            else
            {
                Assert(oldtup == NULL);
                Assert(newtup == NULL);
                ItemPointerSetInvalid(&(new_event.ate_ctid1));
                ItemPointerSetInvalid(&(new_event.ate_ctid2));
            }
            break;
        case TRIGGER_EVENT_UPDATE:
            tgtype_event = TRIGGER_TYPE_UPDATE;
            if (row_trigger)
            {
                Assert(oldtup != NULL);
                Assert(newtup != NULL);
                ItemPointerCopy(&(oldtup->t_self), &(new_event.ate_ctid1));
                ItemPointerCopy(&(newtup->t_self), &(new_event.ate_ctid2));
            }
            else
            {
                Assert(oldtup == NULL);
                Assert(newtup == NULL);
                ItemPointerSetInvalid(&(new_event.ate_ctid1));
                ItemPointerSetInvalid(&(new_event.ate_ctid2));
            }
            break;
        case TRIGGER_EVENT_TRUNCATE:
            tgtype_event = TRIGGER_TYPE_TRUNCATE;
            Assert(oldtup == NULL);
            Assert(newtup == NULL);
            ItemPointerSetInvalid(&(new_event.ate_ctid1));
            ItemPointerSetInvalid(&(new_event.ate_ctid2));
            break;
        default:
            elog(ERROR, "invalid after-trigger event code: %d", event);
            tgtype_event = 0;   /* keep compiler quiet */
            break;
    }

    if (!(relkind == RELKIND_FOREIGN_TABLE && row_trigger))
        new_event.ate_flags = (row_trigger && event == TRIGGER_EVENT_UPDATE) ?
            AFTER_TRIGGER_2CTID : AFTER_TRIGGER_1CTID;
    /* else, we'll initialize ate_flags for each trigger */

    tgtype_level = (row_trigger ? TRIGGER_TYPE_ROW : TRIGGER_TYPE_STATEMENT);

    for (i = 0; i < trigdesc->numtriggers; i++)
    {
        Trigger    *trigger = &trigdesc->triggers[i];

        if (!TRIGGER_TYPE_MATCHES(trigger->tgtype,
                                  tgtype_level,
                                  TRIGGER_TYPE_AFTER,
                                  tgtype_event))
            continue;
        if (!TriggerEnabled(estate, relinfo, trigger, event,
                            modifiedCols, oldtup, newtup))
            continue;

        if (relkind == RELKIND_FOREIGN_TABLE && row_trigger)
        {
            if (fdw_tuplestore == NULL)
            {
                fdw_tuplestore = GetCurrentFDWTuplestore();
                new_event.ate_flags = AFTER_TRIGGER_FDW_FETCH;
            }
            else
                /* subsequent event for the same tuple */
                new_event.ate_flags = AFTER_TRIGGER_FDW_REUSE;
        }

        /*
         * If the trigger is a foreign key enforcement trigger, there are
         * certain cases where we can skip queueing the event because we can
         * tell by inspection that the FK constraint will still pass.
         */
        if (TRIGGER_FIRED_BY_UPDATE(event))
        {
            switch (RI_FKey_trigger_type(trigger->tgfoid))
            {
                case RI_TRIGGER_PK:
                    /* Update on trigger's PK table */
                    if (!RI_FKey_pk_upd_check_required(trigger, rel,
                                                       oldtup, newtup))
                    {
                        /* skip queuing this event */
                        continue;
                    }
                    break;

                case RI_TRIGGER_FK:
                    /* Update on trigger's FK table */
                    if (!RI_FKey_fk_upd_check_required(trigger, rel,
                                                       oldtup, newtup))
                    {
                        /* skip queuing this event */
                        continue;
                    }
                    break;

                case RI_TRIGGER_NONE:
                    /* Not an FK trigger */
                    break;
            }
        }

        /*
         * If the trigger is a deferred unique constraint check trigger, only
         * queue it if the unique constraint was potentially violated, which
         * we know from index insertion time.
         */
        if (trigger->tgfoid == F_UNIQUE_KEY_RECHECK)
        {
            if (!list_member_oid(recheckIndexes, trigger->tgconstrindid))
                continue;       /* Uniqueness definitely not violated */
        }

        /*
         * Fill in event structure and add it to the current query's queue.
         */
        new_shared.ats_event =
            (event & TRIGGER_EVENT_OPMASK) |
            (row_trigger ? TRIGGER_EVENT_ROW : 0) |
            (trigger->tgdeferrable ? AFTER_TRIGGER_DEFERRABLE : 0) |
            (trigger->tginitdeferred ? AFTER_TRIGGER_INITDEFERRED : 0);
        new_shared.ats_tgoid = trigger->tgoid;
        new_shared.ats_relid = RelationGetRelid(rel);
        new_shared.ats_firing_id = 0;

        afterTriggerAddEvent(&afterTriggers.query_stack[afterTriggers.query_depth],
                             &new_event, &new_shared);
    }

    /*
     * Finally, spool any foreign tuple(s).  The tuplestore squashes them to
     * minimal tuples, so this loses any system columns.  The executor lost
     * those columns before us, for an unrelated reason, so this is fine.
     */
    if (fdw_tuplestore)
    {
        if (oldtup != NULL)
            tuplestore_puttuple(fdw_tuplestore, oldtup);
        if (newtup != NULL)
            tuplestore_puttuple(fdw_tuplestore, newtup);
    }
}

Datum
pg_trigger_depth(PG_FUNCTION_ARGS)
{
    PG_RETURN_INT32(MyTriggerDepth);
}