parse_node.c

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/*-------------------------------------------------------------------------
 *
 * parse_node.c
 *    various routines that make nodes for querytrees
 *
 * Portions Copyright (c) 1996-2016, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *    src/backend/parser/parse_node.c
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"

#include "access/heapam.h"
#include "access/htup_details.h"
#include "catalog/pg_type.h"
#include "mb/pg_wchar.h"
#include "nodes/makefuncs.h"
#include "nodes/nodeFuncs.h"
#include "parser/parsetree.h"
#include "parser/parse_coerce.h"
#include "parser/parse_expr.h"
#include "parser/parse_relation.h"
#include "utils/builtins.h"
#include "utils/int8.h"
#include "utils/lsyscache.h"
#include "utils/syscache.h"
#include "utils/varbit.h"


static void pcb_error_callback(void *arg);


/*
 * make_parsestate
 *      Allocate and initialize a new ParseState.
 *
 * Caller should eventually release the ParseState via free_parsestate().
 */
ParseState *
make_parsestate(ParseState *parentParseState)
{
    ParseState *pstate;

    pstate = palloc0(sizeof(ParseState));

    pstate->parentParseState = parentParseState;

    /* Fill in fields that don't start at null/false/zero */
    pstate->p_next_resno = 1;

    if (parentParseState)
    {
        pstate->p_sourcetext = parentParseState->p_sourcetext;
        /* all hooks are copied from parent */
        pstate->p_pre_columnref_hook = parentParseState->p_pre_columnref_hook;
        pstate->p_post_columnref_hook = parentParseState->p_post_columnref_hook;
        pstate->p_paramref_hook = parentParseState->p_paramref_hook;
        pstate->p_coerce_param_hook = parentParseState->p_coerce_param_hook;
        pstate->p_ref_hook_state = parentParseState->p_ref_hook_state;
    }

    return pstate;
}

/*
 * free_parsestate
 *      Release a ParseState and any subsidiary resources.
 */
void
free_parsestate(ParseState *pstate)
{
    /*
     * Check that we did not produce too many resnos; at the very least we
     * cannot allow more than 2^16, since that would exceed the range of a
     * AttrNumber. It seems safest to use MaxTupleAttributeNumber.
     */
    if (pstate->p_next_resno - 1 > MaxTupleAttributeNumber)
        ereport(ERROR,
                (errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
                 errmsg("target lists can have at most %d entries",
                        MaxTupleAttributeNumber)));

    if (pstate->p_target_relation != NULL)
        heap_close(pstate->p_target_relation, NoLock);

    pfree(pstate);
}


/*
 * parser_errposition
 *      Report a parse-analysis-time cursor position, if possible.
 *
 * This is expected to be used within an ereport() call.  The return value
 * is a dummy (always 0, in fact).
 *
 * The locations stored in raw parsetrees are byte offsets into the source
 * string.  We have to convert them to 1-based character indexes for reporting
 * to clients.  (We do things this way to avoid unnecessary overhead in the
 * normal non-error case: computing character indexes would be much more
 * expensive than storing token offsets.)
 */
int
parser_errposition(ParseState *pstate, int location)
{
    int         pos;

    /* No-op if location was not provided */
    if (location < 0)
        return 0;
    /* Can't do anything if source text is not available */
    if (pstate == NULL || pstate->p_sourcetext == NULL)
        return 0;
    /* Convert offset to character number */
    pos = pg_mbstrlen_with_len(pstate->p_sourcetext, location) + 1;
    /* And pass it to the ereport mechanism */
    return errposition(pos);
}


/*
 * setup_parser_errposition_callback
 *      Arrange for non-parser errors to report an error position
 *
 * Sometimes the parser calls functions that aren't part of the parser
 * subsystem and can't reasonably be passed a ParseState; yet we would
 * like any errors thrown in those functions to be tagged with a parse
 * error location.  Use this function to set up an error context stack
 * entry that will accomplish that.  Usage pattern:
 *
 *      declare a local variable "ParseCallbackState pcbstate"
 *      ...
 *      setup_parser_errposition_callback(&pcbstate, pstate, location);
 *      call function that might throw error;
 *      cancel_parser_errposition_callback(&pcbstate);
 */
void
setup_parser_errposition_callback(ParseCallbackState *pcbstate,
                                  ParseState *pstate, int location)
{
    /* Setup error traceback support for ereport() */
    pcbstate->pstate = pstate;
    pcbstate->location = location;
    pcbstate->errcallback.callback = pcb_error_callback;
    pcbstate->errcallback.arg = (void *) pcbstate;
    pcbstate->errcallback.previous = error_context_stack;
    error_context_stack = &pcbstate->errcallback;
}

/*
 * Cancel a previously-set-up errposition callback.
 */
void
cancel_parser_errposition_callback(ParseCallbackState *pcbstate)
{
    /* Pop the error context stack */
    error_context_stack = pcbstate->errcallback.previous;
}

/*
 * Error context callback for inserting parser error location.
 *
 * Note that this will be called for *any* error occurring while the
 * callback is installed.  We avoid inserting an irrelevant error location
 * if the error is a query cancel --- are there any other important cases?
 */
static void
pcb_error_callback(void *arg)
{
    ParseCallbackState *pcbstate = (ParseCallbackState *) arg;

    if (geterrcode() != ERRCODE_QUERY_CANCELED)
        (void) parser_errposition(pcbstate->pstate, pcbstate->location);
}


/*
 * make_var
 *      Build a Var node for an attribute identified by RTE and attrno
 */
Var *
make_var(ParseState *pstate, RangeTblEntry *rte, int attrno, int location)
{
    Var        *result;
    int         vnum,
                sublevels_up;
    Oid         vartypeid;
    int32       type_mod;
    Oid         varcollid;

    vnum = RTERangeTablePosn(pstate, rte, &sublevels_up);
    get_rte_attribute_type(rte, attrno, &vartypeid, &type_mod, &varcollid);
    result = makeVar(vnum, attrno, vartypeid, type_mod, varcollid, sublevels_up);
    result->location = location;
    return result;
}

/*
 * transformArrayType()
 *      Identify the types involved in a subscripting operation
 *
 * On entry, arrayType/arrayTypmod identify the type of the input value
 * to be subscripted (which could be a domain type).  These are modified
 * if necessary to identify the actual array type and typmod, and the
 * array's element type is returned.  An error is thrown if the input isn't
 * an array type.
 */
Oid
transformArrayType(Oid *arrayType, int32 *arrayTypmod)
{
    Oid         origArrayType = *arrayType;
    Oid         elementType;
    HeapTuple   type_tuple_array;
    Form_pg_type type_struct_array;

    /*
     * If the input is a domain, smash to base type, and extract the actual
     * typmod to be applied to the base type.  Subscripting a domain is an
     * operation that necessarily works on the base array type, not the domain
     * itself.  (Note that we provide no method whereby the creator of a
     * domain over an array type could hide its ability to be subscripted.)
     */
    *arrayType = getBaseTypeAndTypmod(*arrayType, arrayTypmod);

    /*
     * We treat int2vector and oidvector as though they were domains over
     * int2[] and oid[].  This is needed because array slicing could create an
     * array that doesn't satisfy the dimensionality constraints of the
     * xxxvector type; so we want the result of a slice operation to be
     * considered to be of the more general type.
     */
    if (*arrayType == INT2VECTOROID)
        *arrayType = INT2ARRAYOID;
    else if (*arrayType == OIDVECTOROID)
        *arrayType = OIDARRAYOID;

    /* Get the type tuple for the array */
    type_tuple_array = SearchSysCache1(TYPEOID, ObjectIdGetDatum(*arrayType));
    if (!HeapTupleIsValid(type_tuple_array))
        elog(ERROR, "cache lookup failed for type %u", *arrayType);
    type_struct_array = (Form_pg_type) GETSTRUCT(type_tuple_array);

    /* needn't check typisdefined since this will fail anyway */

    elementType = type_struct_array->typelem;
    if (elementType == InvalidOid)
        ereport(ERROR,
                (errcode(ERRCODE_DATATYPE_MISMATCH),
                 errmsg("cannot subscript type %s because it is not an array",
                        format_type_be(origArrayType))));

    ReleaseSysCache(type_tuple_array);

    return elementType;
}

/*
 * transformArraySubscripts()
 *      Transform array subscripting.  This is used for both
 *      array fetch and array assignment.
 *
 * In an array fetch, we are given a source array value and we produce an
 * expression that represents the result of extracting a single array element
 * or an array slice.
 *
 * In an array assignment, we are given a destination array value plus a
 * source value that is to be assigned to a single element or a slice of
 * that array.  We produce an expression that represents the new array value
 * with the source data inserted into the right part of the array.
 *
 * For both cases, if the source array is of a domain-over-array type,
 * the result is of the base array type or its element type; essentially,
 * we must fold a domain to its base type before applying subscripting.
 * (Note that int2vector and oidvector are treated as domains here.)
 *
 * pstate       Parse state
 * arrayBase    Already-transformed expression for the array as a whole
 * arrayType    OID of array's datatype (should match type of arrayBase,
 *              or be the base type of arrayBase's domain type)
 * elementType  OID of array's element type (fetch with transformArrayType,
 *              or pass InvalidOid to do it here)
 * arrayTypMod  typmod for the array (which is also typmod for the elements)
 * indirection  Untransformed list of subscripts (must not be NIL)
 * assignFrom   NULL for array fetch, else transformed expression for source.
 */
ArrayRef *
transformArraySubscripts(ParseState *pstate,
                         Node *arrayBase,
                         Oid arrayType,
                         Oid elementType,
                         int32 arrayTypMod,
                         List *indirection,
                         Node *assignFrom)
{
    bool        isSlice = false;
    List       *upperIndexpr = NIL;
    List       *lowerIndexpr = NIL;
    ListCell   *idx;
    ArrayRef   *aref;

    /*
     * Caller may or may not have bothered to determine elementType.  Note
     * that if the caller did do so, arrayType/arrayTypMod must be as modified
     * by transformArrayType, ie, smash domain to base type.
     */
    if (!OidIsValid(elementType))
        elementType = transformArrayType(&arrayType, &arrayTypMod);

    /*
     * A list containing only simple subscripts refers to a single array
     * element.  If any of the items are slice specifiers (lower:upper), then
     * the subscript expression means an array slice operation.  In this case,
     * we convert any non-slice items to slices by treating the single
     * subscript as the upper bound and supplying an assumed lower bound of 1.
     * We have to prescan the list to see if there are any slice items.
     */
    foreach(idx, indirection)
    {
        A_Indices  *ai = (A_Indices *) lfirst(idx);

        if (ai->is_slice)
        {
            isSlice = true;
            break;
        }
    }

    /*
     * Transform the subscript expressions.
     */
    foreach(idx, indirection)
    {
        A_Indices  *ai = (A_Indices *) lfirst(idx);
        Node       *subexpr;

        Assert(IsA(ai, A_Indices));
        if (isSlice)
        {
            if (ai->lidx)
            {
                subexpr = transformExpr(pstate, ai->lidx, pstate->p_expr_kind);
                /* If it's not int4 already, try to coerce */
                subexpr = coerce_to_target_type(pstate,
                                                subexpr, exprType(subexpr),
                                                INT4OID, -1,
                                                COERCION_ASSIGNMENT,
                                                COERCE_IMPLICIT_CAST,
                                                -1);
                if (subexpr == NULL)
                    ereport(ERROR,
                            (errcode(ERRCODE_DATATYPE_MISMATCH),
                             errmsg("array subscript must have type integer"),
                        parser_errposition(pstate, exprLocation(ai->lidx))));
            }
            else if (!ai->is_slice)
            {
                /* Make a constant 1 */
                subexpr = (Node *) makeConst(INT4OID,
                                             -1,
                                             InvalidOid,
                                             sizeof(int32),
                                             Int32GetDatum(1),
                                             false,
                                             true);     /* pass by value */
            }
            else
            {
                /* Slice with omitted lower bound, put NULL into the list */
                subexpr = NULL;
            }
            lowerIndexpr = lappend(lowerIndexpr, subexpr);
        }
        else
            Assert(ai->lidx == NULL && !ai->is_slice);

        if (ai->uidx)
        {
            subexpr = transformExpr(pstate, ai->uidx, pstate->p_expr_kind);
            /* If it's not int4 already, try to coerce */
            subexpr = coerce_to_target_type(pstate,
                                            subexpr, exprType(subexpr),
                                            INT4OID, -1,
                                            COERCION_ASSIGNMENT,
                                            COERCE_IMPLICIT_CAST,
                                            -1);
            if (subexpr == NULL)
                ereport(ERROR,
                        (errcode(ERRCODE_DATATYPE_MISMATCH),
                         errmsg("array subscript must have type integer"),
                         parser_errposition(pstate, exprLocation(ai->uidx))));
        }
        else
        {
            /* Slice with omitted upper bound, put NULL into the list */
            Assert(isSlice && ai->is_slice);
            subexpr = NULL;
        }
        upperIndexpr = lappend(upperIndexpr, subexpr);
    }

    /*
     * If doing an array store, coerce the source value to the right type.
     * (This should agree with the coercion done by transformAssignedExpr.)
     */
    if (assignFrom != NULL)
    {
        Oid         typesource = exprType(assignFrom);
        Oid         typeneeded = isSlice ? arrayType : elementType;
        Node       *newFrom;

        newFrom = coerce_to_target_type(pstate,
                                        assignFrom, typesource,
                                        typeneeded, arrayTypMod,
                                        COERCION_ASSIGNMENT,
                                        COERCE_IMPLICIT_CAST,
                                        -1);
        if (newFrom == NULL)
            ereport(ERROR,
                    (errcode(ERRCODE_DATATYPE_MISMATCH),
                     errmsg("array assignment requires type %s"
                            " but expression is of type %s",
                            format_type_be(typeneeded),
                            format_type_be(typesource)),
                 errhint("You will need to rewrite or cast the expression."),
                     parser_errposition(pstate, exprLocation(assignFrom))));
        assignFrom = newFrom;
    }

    /*
     * Ready to build the ArrayRef node.
     */
    aref = makeNode(ArrayRef);
    aref->refarraytype = arrayType;
    aref->refelemtype = elementType;
    aref->reftypmod = arrayTypMod;
    /* refcollid will be set by parse_collate.c */
    aref->refupperindexpr = upperIndexpr;
    aref->reflowerindexpr = lowerIndexpr;
    aref->refexpr = (Expr *) arrayBase;
    aref->refassgnexpr = (Expr *) assignFrom;

    return aref;
}

/*
 * make_const
 *
 *  Convert a Value node (as returned by the grammar) to a Const node
 *  of the "natural" type for the constant.  Note that this routine is
 *  only used when there is no explicit cast for the constant, so we
 *  have to guess what type is wanted.
 *
 *  For string literals we produce a constant of type UNKNOWN ---- whose
 *  representation is the same as cstring, but it indicates to later type
 *  resolution that we're not sure yet what type it should be considered.
 *  Explicit "NULL" constants are also typed as UNKNOWN.
 *
 *  For integers and floats we produce int4, int8, or numeric depending
 *  on the value of the number.  XXX We should produce int2 as well,
 *  but additional cleanup is needed before we can do that; there are
 *  too many examples that fail if we try.
 */
Const *
make_const(ParseState *pstate, Value *value, int location)
{
    Const      *con;
    Datum       val;
    int64       val64;
    Oid         typeid;
    int         typelen;
    bool        typebyval;
    ParseCallbackState pcbstate;

    switch (nodeTag(value))
    {
        case T_Integer:
            val = Int32GetDatum(intVal(value));

            typeid = INT4OID;
            typelen = sizeof(int32);
            typebyval = true;
            break;

        case T_Float:
            /* could be an oversize integer as well as a float ... */
            if (scanint8(strVal(value), true, &val64))
            {
                /*
                 * It might actually fit in int32. Probably only INT_MIN can
                 * occur, but we'll code the test generally just to be sure.
                 */
                int32       val32 = (int32) val64;

                if (val64 == (int64) val32)
                {
                    val = Int32GetDatum(val32);

                    typeid = INT4OID;
                    typelen = sizeof(int32);
                    typebyval = true;
                }
                else
                {
                    val = Int64GetDatum(val64);

                    typeid = INT8OID;
                    typelen = sizeof(int64);
                    typebyval = FLOAT8PASSBYVAL;        /* int8 and float8 alike */
                }
            }
            else
            {
                /* arrange to report location if numeric_in() fails */
                setup_parser_errposition_callback(&pcbstate, pstate, location);
                val = DirectFunctionCall3(numeric_in,
                                          CStringGetDatum(strVal(value)),
                                          ObjectIdGetDatum(InvalidOid),
                                          Int32GetDatum(-1));
                cancel_parser_errposition_callback(&pcbstate);

                typeid = NUMERICOID;
                typelen = -1;   /* variable len */
                typebyval = false;
            }
            break;

        case T_String:

            /*
             * We assume here that UNKNOWN's internal representation is the
             * same as CSTRING
             */
            val = CStringGetDatum(strVal(value));

            typeid = UNKNOWNOID;    /* will be coerced later */
            typelen = -2;       /* cstring-style varwidth type */
            typebyval = false;
            break;

        case T_BitString:
            /* arrange to report location if bit_in() fails */
            setup_parser_errposition_callback(&pcbstate, pstate, location);
            val = DirectFunctionCall3(bit_in,
                                      CStringGetDatum(strVal(value)),
                                      ObjectIdGetDatum(InvalidOid),
                                      Int32GetDatum(-1));
            cancel_parser_errposition_callback(&pcbstate);
            typeid = BITOID;
            typelen = -1;
            typebyval = false;
            break;

        case T_Null:
            /* return a null const */
            con = makeConst(UNKNOWNOID,
                            -1,
                            InvalidOid,
                            -2,
                            (Datum) 0,
                            true,
                            false);
            con->location = location;
            return con;

        default:
            elog(ERROR, "unrecognized node type: %d", (int) nodeTag(value));
            return NULL;        /* keep compiler quiet */
    }

    con = makeConst(typeid,
                    -1,         /* typmod -1 is OK for all cases */
                    InvalidOid, /* all cases are uncollatable types */
                    typelen,
                    val,
                    false,
                    typebyval);
    con->location = location;

    return con;
}