jsonb_util.c

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/*-------------------------------------------------------------------------
 *
 * jsonb_util.c
 *    converting between Jsonb and JsonbValues, and iterating.
 *
 * Copyright (c) 2014-2016, PostgreSQL Global Development Group
 *
 *
 * IDENTIFICATION
 *    src/backend/utils/adt/jsonb_util.c
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"

#include "access/hash.h"
#include "catalog/pg_collation.h"
#include "miscadmin.h"
#include "utils/builtins.h"
#include "utils/jsonb.h"
#include "utils/memutils.h"

/*
 * Maximum number of elements in an array (or key/value pairs in an object).
 * This is limited by two things: the size of the JEntry array must fit
 * in MaxAllocSize, and the number of elements (or pairs) must fit in the bits
 * reserved for that in the JsonbContainer.header field.
 *
 * (The total size of an array's or object's elements is also limited by
 * JENTRY_OFFLENMASK, but we're not concerned about that here.)
 */
#define JSONB_MAX_ELEMS (Min(MaxAllocSize / sizeof(JsonbValue), JB_CMASK))
#define JSONB_MAX_PAIRS (Min(MaxAllocSize / sizeof(JsonbPair), JB_CMASK))

static void fillJsonbValue(JsonbContainer *container, int index,
               char *base_addr, uint32 offset,
               JsonbValue *result);
static bool equalsJsonbScalarValue(JsonbValue *a, JsonbValue *b);
static int  compareJsonbScalarValue(JsonbValue *a, JsonbValue *b);
static Jsonb *convertToJsonb(JsonbValue *val);
static void convertJsonbValue(StringInfo buffer, JEntry *header, JsonbValue *val, int level);
static void convertJsonbArray(StringInfo buffer, JEntry *header, JsonbValue *val, int level);
static void convertJsonbObject(StringInfo buffer, JEntry *header, JsonbValue *val, int level);
static void convertJsonbScalar(StringInfo buffer, JEntry *header, JsonbValue *scalarVal);

static int  reserveFromBuffer(StringInfo buffer, int len);
static void appendToBuffer(StringInfo buffer, const char *data, int len);
static void copyToBuffer(StringInfo buffer, int offset, const char *data, int len);
static short padBufferToInt(StringInfo buffer);

static JsonbIterator *iteratorFromContainer(JsonbContainer *container, JsonbIterator *parent);
static JsonbIterator *freeAndGetParent(JsonbIterator *it);
static JsonbParseState *pushState(JsonbParseState **pstate);
static void appendKey(JsonbParseState *pstate, JsonbValue *scalarVal);
static void appendValue(JsonbParseState *pstate, JsonbValue *scalarVal);
static void appendElement(JsonbParseState *pstate, JsonbValue *scalarVal);
static int  lengthCompareJsonbStringValue(const void *a, const void *b);
static int  lengthCompareJsonbPair(const void *a, const void *b, void *arg);
static void uniqueifyJsonbObject(JsonbValue *object);
static JsonbValue *pushJsonbValueScalar(JsonbParseState **pstate,
                     JsonbIteratorToken seq,
                     JsonbValue *scalarVal);

/*
 * Turn an in-memory JsonbValue into a Jsonb for on-disk storage.
 *
 * There isn't a JsonbToJsonbValue(), because generally we find it more
 * convenient to directly iterate through the Jsonb representation and only
 * really convert nested scalar values.  JsonbIteratorNext() does this, so that
 * clients of the iteration code don't have to directly deal with the binary
 * representation (JsonbDeepContains() is a notable exception, although all
 * exceptions are internal to this module).  In general, functions that accept
 * a JsonbValue argument are concerned with the manipulation of scalar values,
 * or simple containers of scalar values, where it would be inconvenient to
 * deal with a great amount of other state.
 */
Jsonb *
JsonbValueToJsonb(JsonbValue *val)
{
    Jsonb      *out;

    if (IsAJsonbScalar(val))
    {
        /* Scalar value */
        JsonbParseState *pstate = NULL;
        JsonbValue *res;
        JsonbValue  scalarArray;

        scalarArray.type = jbvArray;
        scalarArray.val.array.rawScalar = true;
        scalarArray.val.array.nElems = 1;

        pushJsonbValue(&pstate, WJB_BEGIN_ARRAY, &scalarArray);
        pushJsonbValue(&pstate, WJB_ELEM, val);
        res = pushJsonbValue(&pstate, WJB_END_ARRAY, NULL);

        out = convertToJsonb(res);
    }
    else if (val->type == jbvObject || val->type == jbvArray)
    {
        out = convertToJsonb(val);
    }
    else
    {
        Assert(val->type == jbvBinary);
        out = palloc(VARHDRSZ + val->val.binary.len);
        SET_VARSIZE(out, VARHDRSZ + val->val.binary.len);
        memcpy(VARDATA(out), val->val.binary.data, val->val.binary.len);
    }

    return out;
}

/*
 * Get the offset of the variable-length portion of a Jsonb node within
 * the variable-length-data part of its container.  The node is identified
 * by index within the container's JEntry array.
 */
uint32
getJsonbOffset(const JsonbContainer *jc, int index)
{
    uint32      offset = 0;
    int         i;

    /*
     * Start offset of this entry is equal to the end offset of the previous
     * entry.  Walk backwards to the most recent entry stored as an end
     * offset, returning that offset plus any lengths in between.
     */
    for (i = index - 1; i >= 0; i--)
    {
        offset += JBE_OFFLENFLD(jc->children[i]);
        if (JBE_HAS_OFF(jc->children[i]))
            break;
    }

    return offset;
}

/*
 * Get the length of the variable-length portion of a Jsonb node.
 * The node is identified by index within the container's JEntry array.
 */
uint32
getJsonbLength(const JsonbContainer *jc, int index)
{
    uint32      off;
    uint32      len;

    /*
     * If the length is stored directly in the JEntry, just return it.
     * Otherwise, get the begin offset of the entry, and subtract that from
     * the stored end+1 offset.
     */
    if (JBE_HAS_OFF(jc->children[index]))
    {
        off = getJsonbOffset(jc, index);
        len = JBE_OFFLENFLD(jc->children[index]) - off;
    }
    else
        len = JBE_OFFLENFLD(jc->children[index]);

    return len;
}

/*
 * BT comparator worker function.  Returns an integer less than, equal to, or
 * greater than zero, indicating whether a is less than, equal to, or greater
 * than b.  Consistent with the requirements for a B-Tree operator class
 *
 * Strings are compared lexically, in contrast with other places where we use a
 * much simpler comparator logic for searching through Strings.  Since this is
 * called from B-Tree support function 1, we're careful about not leaking
 * memory here.
 */
int
compareJsonbContainers(JsonbContainer *a, JsonbContainer *b)
{
    JsonbIterator *ita,
               *itb;
    int         res = 0;

    ita = JsonbIteratorInit(a);
    itb = JsonbIteratorInit(b);

    do
    {
        JsonbValue  va,
                    vb;
        JsonbIteratorToken ra,
                    rb;

        ra = JsonbIteratorNext(&ita, &va, false);
        rb = JsonbIteratorNext(&itb, &vb, false);

        if (ra == rb)
        {
            if (ra == WJB_DONE)
            {
                /* Decisively equal */
                break;
            }

            if (ra == WJB_END_ARRAY || ra == WJB_END_OBJECT)
            {
                /*
                 * There is no array or object to compare at this stage of
                 * processing.  jbvArray/jbvObject values are compared
                 * initially, at the WJB_BEGIN_ARRAY and WJB_BEGIN_OBJECT
                 * tokens.
                 */
                continue;
            }

            if (va.type == vb.type)
            {
                switch (va.type)
                {
                    case jbvString:
                    case jbvNull:
                    case jbvNumeric:
                    case jbvBool:
                        res = compareJsonbScalarValue(&va, &vb);
                        break;
                    case jbvArray:

                        /*
                         * This could be a "raw scalar" pseudo array.  That's
                         * a special case here though, since we still want the
                         * general type-based comparisons to apply, and as far
                         * as we're concerned a pseudo array is just a scalar.
                         */
                        if (va.val.array.rawScalar != vb.val.array.rawScalar)
                            res = (va.val.array.rawScalar) ? -1 : 1;
                        if (va.val.array.nElems != vb.val.array.nElems)
                            res = (va.val.array.nElems > vb.val.array.nElems) ? 1 : -1;
                        break;
                    case jbvObject:
                        if (va.val.object.nPairs != vb.val.object.nPairs)
                            res = (va.val.object.nPairs > vb.val.object.nPairs) ? 1 : -1;
                        break;
                    case jbvBinary:
                        elog(ERROR, "unexpected jbvBinary value");
                }
            }
            else
            {
                /* Type-defined order */
                res = (va.type > vb.type) ? 1 : -1;
            }
        }
        else
        {
            /*
             * It's safe to assume that the types differed, and that the va
             * and vb values passed were set.
             *
             * If the two values were of the same container type, then there'd
             * have been a chance to observe the variation in the number of
             * elements/pairs (when processing WJB_BEGIN_OBJECT, say). They're
             * either two heterogeneously-typed containers, or a container and
             * some scalar type.
             *
             * We don't have to consider the WJB_END_ARRAY and WJB_END_OBJECT
             * cases here, because we would have seen the corresponding
             * WJB_BEGIN_ARRAY and WJB_BEGIN_OBJECT tokens first, and
             * concluded that they don't match.
             */
            Assert(ra != WJB_END_ARRAY && ra != WJB_END_OBJECT);
            Assert(rb != WJB_END_ARRAY && rb != WJB_END_OBJECT);

            Assert(va.type != vb.type);
            Assert(va.type != jbvBinary);
            Assert(vb.type != jbvBinary);
            /* Type-defined order */
            res = (va.type > vb.type) ? 1 : -1;
        }
    }
    while (res == 0);

    while (ita != NULL)
    {
        JsonbIterator *i = ita->parent;

        pfree(ita);
        ita = i;
    }
    while (itb != NULL)
    {
        JsonbIterator *i = itb->parent;

        pfree(itb);
        itb = i;
    }

    return res;
}

/*
 * Find value in object (i.e. the "value" part of some key/value pair in an
 * object), or find a matching element if we're looking through an array.  Do
 * so on the basis of equality of the object keys only, or alternatively
 * element values only, with a caller-supplied value "key".  The "flags"
 * argument allows the caller to specify which container types are of interest.
 *
 * This exported utility function exists to facilitate various cases concerned
 * with "containment".  If asked to look through an object, the caller had
 * better pass a Jsonb String, because their keys can only be strings.
 * Otherwise, for an array, any type of JsonbValue will do.
 *
 * In order to proceed with the search, it is necessary for callers to have
 * both specified an interest in exactly one particular container type with an
 * appropriate flag, as well as having the pointed-to Jsonb container be of
 * one of those same container types at the top level. (Actually, we just do
 * whichever makes sense to save callers the trouble of figuring it out - at
 * most one can make sense, because the container either points to an array
 * (possibly a "raw scalar" pseudo array) or an object.)
 *
 * Note that we can return a jbvBinary JsonbValue if this is called on an
 * object, but we never do so on an array.  If the caller asks to look through
 * a container type that is not of the type pointed to by the container,
 * immediately fall through and return NULL.  If we cannot find the value,
 * return NULL.  Otherwise, return palloc()'d copy of value.
 */
JsonbValue *
findJsonbValueFromContainer(JsonbContainer *container, uint32 flags,
                            JsonbValue *key)
{
    JEntry     *children = container->children;
    int         count = (container->header & JB_CMASK);
    JsonbValue *result;

    Assert((flags & ~(JB_FARRAY | JB_FOBJECT)) == 0);

    /* Quick out without a palloc cycle if object/array is empty */
    if (count <= 0)
        return NULL;

    result = palloc(sizeof(JsonbValue));

    if (flags & JB_FARRAY & container->header)
    {
        char       *base_addr = (char *) (children + count);
        uint32      offset = 0;
        int         i;

        for (i = 0; i < count; i++)
        {
            fillJsonbValue(container, i, base_addr, offset, result);

            if (key->type == result->type)
            {
                if (equalsJsonbScalarValue(key, result))
                    return result;
            }

            JBE_ADVANCE_OFFSET(offset, children[i]);
        }
    }
    else if (flags & JB_FOBJECT & container->header)
    {
        /* Since this is an object, account for *Pairs* of Jentrys */
        char       *base_addr = (char *) (children + count * 2);
        uint32      stopLow = 0,
                    stopHigh = count;

        /* Object key passed by caller must be a string */
        Assert(key->type == jbvString);

        /* Binary search on object/pair keys *only* */
        while (stopLow < stopHigh)
        {
            uint32      stopMiddle;
            int         difference;
            JsonbValue  candidate;

            stopMiddle = stopLow + (stopHigh - stopLow) / 2;

            candidate.type = jbvString;
            candidate.val.string.val =
                base_addr + getJsonbOffset(container, stopMiddle);
            candidate.val.string.len = getJsonbLength(container, stopMiddle);

            difference = lengthCompareJsonbStringValue(&candidate, key);

            if (difference == 0)
            {
                /* Found our key, return corresponding value */
                int         index = stopMiddle + count;

                fillJsonbValue(container, index, base_addr,
                               getJsonbOffset(container, index),
                               result);

                return result;
            }
            else
            {
                if (difference < 0)
                    stopLow = stopMiddle + 1;
                else
                    stopHigh = stopMiddle;
            }
        }
    }

    /* Not found */
    pfree(result);
    return NULL;
}

/*
 * Get i-th value of a Jsonb array.
 *
 * Returns palloc()'d copy of the value, or NULL if it does not exist.
 */
JsonbValue *
getIthJsonbValueFromContainer(JsonbContainer *container, uint32 i)
{
    JsonbValue *result;
    char       *base_addr;
    uint32      nelements;

    if ((container->header & JB_FARRAY) == 0)
        elog(ERROR, "not a jsonb array");

    nelements = container->header & JB_CMASK;
    base_addr = (char *) &container->children[nelements];

    if (i >= nelements)
        return NULL;

    result = palloc(sizeof(JsonbValue));

    fillJsonbValue(container, i, base_addr,
                   getJsonbOffset(container, i),
                   result);

    return result;
}

/*
 * A helper function to fill in a JsonbValue to represent an element of an
 * array, or a key or value of an object.
 *
 * The node's JEntry is at container->children[index], and its variable-length
 * data is at base_addr + offset.  We make the caller determine the offset
 * since in many cases the caller can amortize that work across multiple
 * children.  When it can't, it can just call getJsonbOffset().
 *
 * A nested array or object will be returned as jbvBinary, ie. it won't be
 * expanded.
 */
static void
fillJsonbValue(JsonbContainer *container, int index,
               char *base_addr, uint32 offset,
               JsonbValue *result)
{
    JEntry      entry = container->children[index];

    if (JBE_ISNULL(entry))
    {
        result->type = jbvNull;
    }
    else if (JBE_ISSTRING(entry))
    {
        result->type = jbvString;
        result->val.string.val = base_addr + offset;
        result->val.string.len = getJsonbLength(container, index);
        Assert(result->val.string.len >= 0);
    }
    else if (JBE_ISNUMERIC(entry))
    {
        result->type = jbvNumeric;
        result->val.numeric = (Numeric) (base_addr + INTALIGN(offset));
    }
    else if (JBE_ISBOOL_TRUE(entry))
    {
        result->type = jbvBool;
        result->val.boolean = true;
    }
    else if (JBE_ISBOOL_FALSE(entry))
    {
        result->type = jbvBool;
        result->val.boolean = false;
    }
    else
    {
        Assert(JBE_ISCONTAINER(entry));
        result->type = jbvBinary;
        /* Remove alignment padding from data pointer and length */
        result->val.binary.data = (JsonbContainer *) (base_addr + INTALIGN(offset));
        result->val.binary.len = getJsonbLength(container, index) -
            (INTALIGN(offset) - offset);
    }
}

/*
 * Push JsonbValue into JsonbParseState.
 *
 * Used when parsing JSON tokens to form Jsonb, or when converting an in-memory
 * JsonbValue to a Jsonb.
 *
 * Initial state of *JsonbParseState is NULL, since it'll be allocated here
 * originally (caller will get JsonbParseState back by reference).
 *
 * Only sequential tokens pertaining to non-container types should pass a
 * JsonbValue.  There is one exception -- WJB_BEGIN_ARRAY callers may pass a
 * "raw scalar" pseudo array to append it - the actual scalar should be passed
 * next and it will be added as the only member of the array.
 *
 * Values of type jvbBinary, which are rolled up arrays and objects,
 * are unpacked before being added to the result.
 */
JsonbValue *
pushJsonbValue(JsonbParseState **pstate, JsonbIteratorToken seq,
               JsonbValue *jbval)
{
    JsonbIterator *it;
    JsonbValue *res = NULL;
    JsonbValue  v;
    JsonbIteratorToken tok;

    if (!jbval || (seq != WJB_ELEM && seq != WJB_VALUE) ||
        jbval->type != jbvBinary)
    {
        /* drop through */
        return pushJsonbValueScalar(pstate, seq, jbval);
    }

    /* unpack the binary and add each piece to the pstate */
    it = JsonbIteratorInit(jbval->val.binary.data);
    while ((tok = JsonbIteratorNext(&it, &v, false)) != WJB_DONE)
        res = pushJsonbValueScalar(pstate, tok,
                                   tok < WJB_BEGIN_ARRAY ? &v : NULL);

    return res;
}

/*
 * Do the actual pushing, with only scalar or pseudo-scalar-array values
 * accepted.
 */
static JsonbValue *
pushJsonbValueScalar(JsonbParseState **pstate, JsonbIteratorToken seq,
                     JsonbValue *scalarVal)
{
    JsonbValue *result = NULL;

    switch (seq)
    {
        case WJB_BEGIN_ARRAY:
            Assert(!scalarVal || scalarVal->val.array.rawScalar);
            *pstate = pushState(pstate);
            result = &(*pstate)->contVal;
            (*pstate)->contVal.type = jbvArray;
            (*pstate)->contVal.val.array.nElems = 0;
            (*pstate)->contVal.val.array.rawScalar = (scalarVal &&
                                             scalarVal->val.array.rawScalar);
            if (scalarVal && scalarVal->val.array.nElems > 0)
            {
                /* Assume that this array is still really a scalar */
                Assert(scalarVal->type == jbvArray);
                (*pstate)->size = scalarVal->val.array.nElems;
            }
            else
            {
                (*pstate)->size = 4;
            }
            (*pstate)->contVal.val.array.elems = palloc(sizeof(JsonbValue) *
                                                        (*pstate)->size);
            break;
        case WJB_BEGIN_OBJECT:
            Assert(!scalarVal);
            *pstate = pushState(pstate);
            result = &(*pstate)->contVal;
            (*pstate)->contVal.type = jbvObject;
            (*pstate)->contVal.val.object.nPairs = 0;
            (*pstate)->size = 4;
            (*pstate)->contVal.val.object.pairs = palloc(sizeof(JsonbPair) *
                                                         (*pstate)->size);
            break;
        case WJB_KEY:
            Assert(scalarVal->type == jbvString);
            appendKey(*pstate, scalarVal);
            break;
        case WJB_VALUE:
            Assert(IsAJsonbScalar(scalarVal));
            appendValue(*pstate, scalarVal);
            break;
        case WJB_ELEM:
            Assert(IsAJsonbScalar(scalarVal));
            appendElement(*pstate, scalarVal);
            break;
        case WJB_END_OBJECT:
            uniqueifyJsonbObject(&(*pstate)->contVal);
            /* fall through! */
        case WJB_END_ARRAY:
            /* Steps here common to WJB_END_OBJECT case */
            Assert(!scalarVal);
            result = &(*pstate)->contVal;

            /*
             * Pop stack and push current array/object as value in parent
             * array/object
             */
            *pstate = (*pstate)->next;
            if (*pstate)
            {
                switch ((*pstate)->contVal.type)
                {
                    case jbvArray:
                        appendElement(*pstate, result);
                        break;
                    case jbvObject:
                        appendValue(*pstate, result);
                        break;
                    default:
                        elog(ERROR, "invalid jsonb container type");
                }
            }
            break;
        default:
            elog(ERROR, "unrecognized jsonb sequential processing token");
    }

    return result;
}

/*
 * pushJsonbValue() worker:  Iteration-like forming of Jsonb
 */
static JsonbParseState *
pushState(JsonbParseState **pstate)
{
    JsonbParseState *ns = palloc(sizeof(JsonbParseState));

    ns->next = *pstate;
    return ns;
}

/*
 * pushJsonbValue() worker:  Append a pair key to state when generating a Jsonb
 */
static void
appendKey(JsonbParseState *pstate, JsonbValue *string)
{
    JsonbValue *object = &pstate->contVal;

    Assert(object->type == jbvObject);
    Assert(string->type == jbvString);

    if (object->val.object.nPairs >= JSONB_MAX_PAIRS)
        ereport(ERROR,
                (errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
                 errmsg("number of jsonb object pairs exceeds the maximum allowed (%zu)",
                        JSONB_MAX_PAIRS)));

    if (object->val.object.nPairs >= pstate->size)
    {
        pstate->size *= 2;
        object->val.object.pairs = repalloc(object->val.object.pairs,
                                            sizeof(JsonbPair) * pstate->size);
    }

    object->val.object.pairs[object->val.object.nPairs].key = *string;
    object->val.object.pairs[object->val.object.nPairs].order = object->val.object.nPairs;
}

/*
 * pushJsonbValue() worker:  Append a pair value to state when generating a
 * Jsonb
 */
static void
appendValue(JsonbParseState *pstate, JsonbValue *scalarVal)
{
    JsonbValue *object = &pstate->contVal;

    Assert(object->type == jbvObject);

    object->val.object.pairs[object->val.object.nPairs++].value = *scalarVal;
}

/*
 * pushJsonbValue() worker:  Append an element to state when generating a Jsonb
 */
static void
appendElement(JsonbParseState *pstate, JsonbValue *scalarVal)
{
    JsonbValue *array = &pstate->contVal;

    Assert(array->type == jbvArray);

    if (array->val.array.nElems >= JSONB_MAX_ELEMS)
        ereport(ERROR,
                (errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
                 errmsg("number of jsonb array elements exceeds the maximum allowed (%zu)",
                        JSONB_MAX_ELEMS)));

    if (array->val.array.nElems >= pstate->size)
    {
        pstate->size *= 2;
        array->val.array.elems = repalloc(array->val.array.elems,
                                          sizeof(JsonbValue) * pstate->size);
    }

    array->val.array.elems[array->val.array.nElems++] = *scalarVal;
}

/*
 * Given a JsonbContainer, expand to JsonbIterator to iterate over items
 * fully expanded to in-memory representation for manipulation.
 *
 * See JsonbIteratorNext() for notes on memory management.
 */
JsonbIterator *
JsonbIteratorInit(JsonbContainer *container)
{
    return iteratorFromContainer(container, NULL);
}

/*
 * Get next JsonbValue while iterating
 *
 * Caller should initially pass their own, original iterator.  They may get
 * back a child iterator palloc()'d here instead.  The function can be relied
 * on to free those child iterators, lest the memory allocated for highly
 * nested objects become unreasonable, but only if callers don't end iteration
 * early (by breaking upon having found something in a search, for example).
 *
 * Callers in such a scenario, that are particularly sensitive to leaking
 * memory in a long-lived context may walk the ancestral tree from the final
 * iterator we left them with to its oldest ancestor, pfree()ing as they go.
 * They do not have to free any other memory previously allocated for iterators
 * but not accessible as direct ancestors of the iterator they're last passed
 * back.
 *
 * Returns "Jsonb sequential processing" token value.  Iterator "state"
 * reflects the current stage of the process in a less granular fashion, and is
 * mostly used here to track things internally with respect to particular
 * iterators.
 *
 * Clients of this function should not have to handle any jbvBinary values
 * (since recursive calls will deal with this), provided skipNested is false.
 * It is our job to expand the jbvBinary representation without bothering them
 * with it.  However, clients should not take it upon themselves to touch array
 * or Object element/pair buffers, since their element/pair pointers are
 * garbage.  Also, *val will not be set when returning WJB_END_ARRAY or
 * WJB_END_OBJECT, on the assumption that it's only useful to access values
 * when recursing in.
 */
JsonbIteratorToken
JsonbIteratorNext(JsonbIterator **it, JsonbValue *val, bool skipNested)
{
    if (*it == NULL)
        return WJB_DONE;

    /*
     * When stepping into a nested container, we jump back here to start
     * processing the child. We will not recurse further in one call, because
     * processing the child will always begin in JBI_ARRAY_START or
     * JBI_OBJECT_START state.
     */
recurse:
    switch ((*it)->state)
    {
        case JBI_ARRAY_START:
            /* Set v to array on first array call */
            val->type = jbvArray;
            val->val.array.nElems = (*it)->nElems;

            /*
             * v->val.array.elems is not actually set, because we aren't doing
             * a full conversion
             */
            val->val.array.rawScalar = (*it)->isScalar;
            (*it)->curIndex = 0;
            (*it)->curDataOffset = 0;
            (*it)->curValueOffset = 0;  /* not actually used */
            /* Set state for next call */
            (*it)->state = JBI_ARRAY_ELEM;
            return WJB_BEGIN_ARRAY;

        case JBI_ARRAY_ELEM:
            if ((*it)->curIndex >= (*it)->nElems)
            {
                /*
                 * All elements within array already processed.  Report this
                 * to caller, and give it back original parent iterator (which
                 * independently tracks iteration progress at its level of
                 * nesting).
                 */
                *it = freeAndGetParent(*it);
                return WJB_END_ARRAY;
            }

            fillJsonbValue((*it)->container, (*it)->curIndex,
                           (*it)->dataProper, (*it)->curDataOffset,
                           val);

            JBE_ADVANCE_OFFSET((*it)->curDataOffset,
                               (*it)->children[(*it)->curIndex]);
            (*it)->curIndex++;

            if (!IsAJsonbScalar(val) && !skipNested)
            {
                /* Recurse into container. */
                *it = iteratorFromContainer(val->val.binary.data, *it);
                goto recurse;
            }
            else
            {
                /*
                 * Scalar item in array, or a container and caller didn't want
                 * us to recurse into it.
                 */
                return WJB_ELEM;
            }

        case JBI_OBJECT_START:
            /* Set v to object on first object call */
            val->type = jbvObject;
            val->val.object.nPairs = (*it)->nElems;

            /*
             * v->val.object.pairs is not actually set, because we aren't
             * doing a full conversion
             */
            (*it)->curIndex = 0;
            (*it)->curDataOffset = 0;
            (*it)->curValueOffset = getJsonbOffset((*it)->container,
                                                   (*it)->nElems);
            /* Set state for next call */
            (*it)->state = JBI_OBJECT_KEY;
            return WJB_BEGIN_OBJECT;

        case JBI_OBJECT_KEY:
            if ((*it)->curIndex >= (*it)->nElems)
            {
                /*
                 * All pairs within object already processed.  Report this to
                 * caller, and give it back original containing iterator
                 * (which independently tracks iteration progress at its level
                 * of nesting).
                 */
                *it = freeAndGetParent(*it);
                return WJB_END_OBJECT;
            }
            else
            {
                /* Return key of a key/value pair.  */
                fillJsonbValue((*it)->container, (*it)->curIndex,
                               (*it)->dataProper, (*it)->curDataOffset,
                               val);
                if (val->type != jbvString)
                    elog(ERROR, "unexpected jsonb type as object key");

                /* Set state for next call */
                (*it)->state = JBI_OBJECT_VALUE;
                return WJB_KEY;
            }

        case JBI_OBJECT_VALUE:
            /* Set state for next call */
            (*it)->state = JBI_OBJECT_KEY;

            fillJsonbValue((*it)->container, (*it)->curIndex + (*it)->nElems,
                           (*it)->dataProper, (*it)->curValueOffset,
                           val);

            JBE_ADVANCE_OFFSET((*it)->curDataOffset,
                               (*it)->children[(*it)->curIndex]);
            JBE_ADVANCE_OFFSET((*it)->curValueOffset,
                           (*it)->children[(*it)->curIndex + (*it)->nElems]);
            (*it)->curIndex++;

            /*
             * Value may be a container, in which case we recurse with new,
             * child iterator (unless the caller asked not to, by passing
             * skipNested).
             */
            if (!IsAJsonbScalar(val) && !skipNested)
            {
                *it = iteratorFromContainer(val->val.binary.data, *it);
                goto recurse;
            }
            else
                return WJB_VALUE;
    }

    elog(ERROR, "invalid iterator state");
    return -1;
}

/*
 * Initialize an iterator for iterating all elements in a container.
 */
static JsonbIterator *
iteratorFromContainer(JsonbContainer *container, JsonbIterator *parent)
{
    JsonbIterator *it;

    it = palloc(sizeof(JsonbIterator));
    it->container = container;
    it->parent = parent;
    it->nElems = container->header & JB_CMASK;

    /* Array starts just after header */
    it->children = container->children;

    switch (container->header & (JB_FARRAY | JB_FOBJECT))
    {
        case JB_FARRAY:
            it->dataProper =
                (char *) it->children + it->nElems * sizeof(JEntry);
            it->isScalar = (container->header & JB_FSCALAR) != 0;
            /* This is either a "raw scalar", or an array */
            Assert(!it->isScalar || it->nElems == 1);

            it->state = JBI_ARRAY_START;
            break;

        case JB_FOBJECT:
            it->dataProper =
                (char *) it->children + it->nElems * sizeof(JEntry) * 2;
            it->state = JBI_OBJECT_START;
            break;

        default:
            elog(ERROR, "unknown type of jsonb container");
    }

    return it;
}

/*
 * JsonbIteratorNext() worker:  Return parent, while freeing memory for current
 * iterator
 */
static JsonbIterator *
freeAndGetParent(JsonbIterator *it)
{
    JsonbIterator *v = it->parent;

    pfree(it);
    return v;
}

/*
 * Worker for "contains" operator's function
 *
 * Formally speaking, containment is top-down, unordered subtree isomorphism.
 *
 * Takes iterators that belong to some container type.  These iterators
 * "belong" to those values in the sense that they've just been initialized in
 * respect of them by the caller (perhaps in a nested fashion).
 *
 * "val" is lhs Jsonb, and mContained is rhs Jsonb when called from top level.
 * We determine if mContained is contained within val.
 */
bool
JsonbDeepContains(JsonbIterator **val, JsonbIterator **mContained)
{
    JsonbValue  vval,
                vcontained;
    JsonbIteratorToken rval,
                rcont;

    /*
     * Guard against stack overflow due to overly complex Jsonb.
     *
     * Functions called here independently take this precaution, but that
     * might not be sufficient since this is also a recursive function.
     */
    check_stack_depth();

    rval = JsonbIteratorNext(val, &vval, false);
    rcont = JsonbIteratorNext(mContained, &vcontained, false);

    if (rval != rcont)
    {
        /*
         * The differing return values can immediately be taken as indicating
         * two differing container types at this nesting level, which is
         * sufficient reason to give up entirely (but it should be the case
         * that they're both some container type).
         */
        Assert(rval == WJB_BEGIN_OBJECT || rval == WJB_BEGIN_ARRAY);
        Assert(rcont == WJB_BEGIN_OBJECT || rcont == WJB_BEGIN_ARRAY);
        return false;
    }
    else if (rcont == WJB_BEGIN_OBJECT)
    {
        Assert(vval.type == jbvObject);
        Assert(vcontained.type == jbvObject);

        /*
         * If the lhs has fewer pairs than the rhs, it can't possibly contain
         * the rhs.  (This conclusion is safe only because we de-duplicate
         * keys in all Jsonb objects; thus there can be no corresponding
         * optimization in the array case.)  The case probably won't arise
         * often, but since it's such a cheap check we may as well make it.
         */
        if (vval.val.object.nPairs < vcontained.val.object.nPairs)
            return false;

        /* Work through rhs "is it contained within?" object */
        for (;;)
        {
            JsonbValue *lhsVal; /* lhsVal is from pair in lhs object */

            rcont = JsonbIteratorNext(mContained, &vcontained, false);

            /*
             * When we get through caller's rhs "is it contained within?"
             * object without failing to find one of its values, it's
             * contained.
             */
            if (rcont == WJB_END_OBJECT)
                return true;

            Assert(rcont == WJB_KEY);

            /* First, find value by key... */
            lhsVal = findJsonbValueFromContainer((*val)->container,
                                                 JB_FOBJECT,
                                                 &vcontained);

            if (!lhsVal)
                return false;

            /*
             * ...at this stage it is apparent that there is at least a key
             * match for this rhs pair.
             */
            rcont = JsonbIteratorNext(mContained, &vcontained, true);

            Assert(rcont == WJB_VALUE);

            /*
             * Compare rhs pair's value with lhs pair's value just found using
             * key
             */
            if (lhsVal->type != vcontained.type)
            {
                return false;
            }
            else if (IsAJsonbScalar(lhsVal))
            {
                if (!equalsJsonbScalarValue(lhsVal, &vcontained))
                    return false;
            }
            else
            {
                /* Nested container value (object or array) */
                JsonbIterator *nestval,
                           *nestContained;

                Assert(lhsVal->type == jbvBinary);
                Assert(vcontained.type == jbvBinary);

                nestval = JsonbIteratorInit(lhsVal->val.binary.data);
                nestContained = JsonbIteratorInit(vcontained.val.binary.data);

                /*
                 * Match "value" side of rhs datum object's pair recursively.
                 * It's a nested structure.
                 *
                 * Note that nesting still has to "match up" at the right
                 * nesting sub-levels.  However, there need only be zero or
                 * more matching pairs (or elements) at each nesting level
                 * (provided the *rhs* pairs/elements *all* match on each
                 * level), which enables searching nested structures for a
                 * single String or other primitive type sub-datum quite
                 * effectively (provided the user constructed the rhs nested
                 * structure such that we "know where to look").
                 *
                 * In other words, the mapping of container nodes in the rhs
                 * "vcontained" Jsonb to internal nodes on the lhs is
                 * injective, and parent-child edges on the rhs must be mapped
                 * to parent-child edges on the lhs to satisfy the condition
                 * of containment (plus of course the mapped nodes must be
                 * equal).
                 */
                if (!JsonbDeepContains(&nestval, &nestContained))
                    return false;
            }
        }
    }
    else if (rcont == WJB_BEGIN_ARRAY)
    {
        JsonbValue *lhsConts = NULL;
        uint32      nLhsElems = vval.val.array.nElems;

        Assert(vval.type == jbvArray);
        Assert(vcontained.type == jbvArray);

        /*
         * Handle distinction between "raw scalar" pseudo arrays, and real
         * arrays.
         *
         * A raw scalar may contain another raw scalar, and an array may
         * contain a raw scalar, but a raw scalar may not contain an array. We
         * don't do something like this for the object case, since objects can
         * only contain pairs, never raw scalars (a pair is represented by an
         * rhs object argument with a single contained pair).
         */
        if (vval.val.array.rawScalar && !vcontained.val.array.rawScalar)
            return false;

        /* Work through rhs "is it contained within?" array */
        for (;;)
        {
            rcont = JsonbIteratorNext(mContained, &vcontained, true);

            /*
             * When we get through caller's rhs "is it contained within?"
             * array without failing to find one of its values, it's
             * contained.
             */
            if (rcont == WJB_END_ARRAY)
                return true;

            Assert(rcont == WJB_ELEM);

            if (IsAJsonbScalar(&vcontained))
            {
                if (!findJsonbValueFromContainer((*val)->container,
                                                 JB_FARRAY,
                                                 &vcontained))
                    return false;
            }
            else
            {
                uint32      i;

                /*
                 * If this is first container found in rhs array (at this
                 * depth), initialize temp lhs array of containers
                 */
                if (lhsConts == NULL)
                {
                    uint32      j = 0;

                    /* Make room for all possible values */
                    lhsConts = palloc(sizeof(JsonbValue) * nLhsElems);

                    for (i = 0; i < nLhsElems; i++)
                    {
                        /* Store all lhs elements in temp array */
                        rcont = JsonbIteratorNext(val, &vval, true);
                        Assert(rcont == WJB_ELEM);

                        if (vval.type == jbvBinary)
                            lhsConts[j++] = vval;
                    }

                    /* No container elements in temp array, so give up now */
                    if (j == 0)
                        return false;

                    /* We may have only partially filled array */
                    nLhsElems = j;
                }

                /* XXX: Nested array containment is O(N^2) */
                for (i = 0; i < nLhsElems; i++)
                {
                    /* Nested container value (object or array) */
                    JsonbIterator *nestval,
                               *nestContained;
                    bool        contains;

                    nestval = JsonbIteratorInit(lhsConts[i].val.binary.data);
                    nestContained = JsonbIteratorInit(vcontained.val.binary.data);

                    contains = JsonbDeepContains(&nestval, &nestContained);

                    if (nestval)
                        pfree(nestval);
                    if (nestContained)
                        pfree(nestContained);
                    if (contains)
                        break;
                }

                /*
                 * Report rhs container value is not contained if couldn't
                 * match rhs container to *some* lhs cont
                 */
                if (i == nLhsElems)
                    return false;
            }
        }
    }
    else
    {
        elog(ERROR, "invalid jsonb container type");
    }

    elog(ERROR, "unexpectedly fell off end of jsonb container");
    return false;
}

/*
 * Hash a JsonbValue scalar value, mixing the hash value into an existing
 * hash provided by the caller.
 *
 * Some callers may wish to independently XOR in JB_FOBJECT and JB_FARRAY
 * flags.
 */
void
JsonbHashScalarValue(const JsonbValue *scalarVal, uint32 *hash)
{
    uint32      tmp;

    /* Compute hash value for scalarVal */
    switch (scalarVal->type)
    {
        case jbvNull:
            tmp = 0x01;
            break;
        case jbvString:
            tmp = DatumGetUInt32(hash_any((const unsigned char *) scalarVal->val.string.val,
                                          scalarVal->val.string.len));
            break;
        case jbvNumeric:
            /* Must hash equal numerics to equal hash codes */
            tmp = DatumGetUInt32(DirectFunctionCall1(hash_numeric,
                                   NumericGetDatum(scalarVal->val.numeric)));
            break;
        case jbvBool:
            tmp = scalarVal->val.boolean ? 0x02 : 0x04;

            break;
        default:
            elog(ERROR, "invalid jsonb scalar type");
            tmp = 0;            /* keep compiler quiet */
            break;
    }

    /*
     * Combine hash values of successive keys, values and elements by rotating
     * the previous value left 1 bit, then XOR'ing in the new
     * key/value/element's hash value.
     */
    *hash = (*hash << 1) | (*hash >> 31);
    *hash ^= tmp;
}

/*
 * Are two scalar JsonbValues of the same type a and b equal?
 */
static bool
equalsJsonbScalarValue(JsonbValue *aScalar, JsonbValue *bScalar)
{
    if (aScalar->type == bScalar->type)
    {
        switch (aScalar->type)
        {
            case jbvNull:
                return true;
            case jbvString:
                return lengthCompareJsonbStringValue(aScalar, bScalar) == 0;
            case jbvNumeric:
                return DatumGetBool(DirectFunctionCall2(numeric_eq,
                                       PointerGetDatum(aScalar->val.numeric),
                                     PointerGetDatum(bScalar->val.numeric)));
            case jbvBool:
                return aScalar->val.boolean == bScalar->val.boolean;

            default:
                elog(ERROR, "invalid jsonb scalar type");
        }
    }
    elog(ERROR, "jsonb scalar type mismatch");
    return -1;
}

/*
 * Compare two scalar JsonbValues, returning -1, 0, or 1.
 *
 * Strings are compared using the default collation.  Used by B-tree
 * operators, where a lexical sort order is generally expected.
 */
static int
compareJsonbScalarValue(JsonbValue *aScalar, JsonbValue *bScalar)
{
    if (aScalar->type == bScalar->type)
    {
        switch (aScalar->type)
        {
            case jbvNull:
                return 0;
            case jbvString:
                return varstr_cmp(aScalar->val.string.val,
                                  aScalar->val.string.len,
                                  bScalar->val.string.val,
                                  bScalar->val.string.len,
                                  DEFAULT_COLLATION_OID);
            case jbvNumeric:
                return DatumGetInt32(DirectFunctionCall2(numeric_cmp,
                                       PointerGetDatum(aScalar->val.numeric),
                                     PointerGetDatum(bScalar->val.numeric)));
            case jbvBool:
                if (aScalar->val.boolean == bScalar->val.boolean)
                    return 0;
                else if (aScalar->val.boolean > bScalar->val.boolean)
                    return 1;
                else
                    return -1;
            default:
                elog(ERROR, "invalid jsonb scalar type");
        }
    }
    elog(ERROR, "jsonb scalar type mismatch");
    return -1;
}


/*
 * Functions for manipulating the resizeable buffer used by convertJsonb and
 * its subroutines.
 */

/*
 * Reserve 'len' bytes, at the end of the buffer, enlarging it if necessary.
 * Returns the offset to the reserved area. The caller is expected to fill
 * the reserved area later with copyToBuffer().
 */
static int
reserveFromBuffer(StringInfo buffer, int len)
{
    int         offset;

    /* Make more room if needed */
    enlargeStringInfo(buffer, len);

    /* remember current offset */
    offset = buffer->len;

    /* reserve the space */
    buffer->len += len;

    /*
     * Keep a trailing null in place, even though it's not useful for us; it
     * seems best to preserve the invariants of StringInfos.
     */
    buffer->data[buffer->len] = '\0';

    return offset;
}

/*
 * Copy 'len' bytes to a previously reserved area in buffer.
 */
static void
copyToBuffer(StringInfo buffer, int offset, const char *data, int len)
{
    memcpy(buffer->data + offset, data, len);
}

/*
 * A shorthand for reserveFromBuffer + copyToBuffer.
 */
static void
appendToBuffer(StringInfo buffer, const char *data, int len)
{
    int         offset;

    offset = reserveFromBuffer(buffer, len);
    copyToBuffer(buffer, offset, data, len);
}


/*
 * Append padding, so that the length of the StringInfo is int-aligned.
 * Returns the number of padding bytes appended.
 */
static short
padBufferToInt(StringInfo buffer)
{
    int         padlen,
                p,
                offset;

    padlen = INTALIGN(buffer->len) - buffer->len;

    offset = reserveFromBuffer(buffer, padlen);

    /* padlen must be small, so this is probably faster than a memset */
    for (p = 0; p < padlen; p++)
        buffer->data[offset + p] = '\0';

    return padlen;
}

/*
 * Given a JsonbValue, convert to Jsonb. The result is palloc'd.
 */
static Jsonb *
convertToJsonb(JsonbValue *val)
{
    StringInfoData buffer;
    JEntry      jentry;
    Jsonb      *res;

    /* Should not already have binary representation */
    Assert(val->type != jbvBinary);

    /* Allocate an output buffer. It will be enlarged as needed */
    initStringInfo(&buffer);

    /* Make room for the varlena header */
    reserveFromBuffer(&buffer, VARHDRSZ);

    convertJsonbValue(&buffer, &jentry, val, 0);

    /*
     * Note: the JEntry of the root is discarded. Therefore the root
     * JsonbContainer struct must contain enough information to tell what kind
     * of value it is.
     */

    res = (Jsonb *) buffer.data;

    SET_VARSIZE(res, buffer.len);

    return res;
}

/*
 * Subroutine of convertJsonb: serialize a single JsonbValue into buffer.
 *
 * The JEntry header for this node is returned in *header.  It is filled in
 * with the length of this value and appropriate type bits.  If we wish to
 * store an end offset rather than a length, it is the caller's responsibility
 * to adjust for that.
 *
 * If the value is an array or an object, this recurses. 'level' is only used
 * for debugging purposes.
 */
static void
convertJsonbValue(StringInfo buffer, JEntry *header, JsonbValue *val, int level)
{
    check_stack_depth();

    if (!val)
        return;

    /*
     * A JsonbValue passed as val should never have a type of jbvBinary, and
     * neither should any of its sub-components. Those values will be produced
     * by convertJsonbArray and convertJsonbObject, the results of which will
     * not be passed back to this function as an argument.
     */

    if (IsAJsonbScalar(val))
        convertJsonbScalar(buffer, header, val);
    else if (val->type == jbvArray)
        convertJsonbArray(buffer, header, val, level);
    else if (val->type == jbvObject)
        convertJsonbObject(buffer, header, val, level);
    else
        elog(ERROR, "unknown type of jsonb container to convert");
}

static void
convertJsonbArray(StringInfo buffer, JEntry *pheader, JsonbValue *val, int level)
{
    int         base_offset;
    int         jentry_offset;
    int         i;
    int         totallen;
    uint32      header;
    int         nElems = val->val.array.nElems;

    /* Remember where in the buffer this array starts. */
    base_offset = buffer->len;

    /* Align to 4-byte boundary (any padding counts as part of my data) */
    padBufferToInt(buffer);

    /*
     * Construct the header Jentry and store it in the beginning of the
     * variable-length payload.
     */
    header = nElems | JB_FARRAY;
    if (val->val.array.rawScalar)
    {
        Assert(nElems == 1);
        Assert(level == 0);
        header |= JB_FSCALAR;
    }

    appendToBuffer(buffer, (char *) &header, sizeof(uint32));

    /* Reserve space for the JEntries of the elements. */
    jentry_offset = reserveFromBuffer(buffer, sizeof(JEntry) * nElems);

    totallen = 0;
    for (i = 0; i < nElems; i++)
    {
        JsonbValue *elem = &val->val.array.elems[i];
        int         len;
        JEntry      meta;

        /*
         * Convert element, producing a JEntry and appending its
         * variable-length data to buffer
         */
        convertJsonbValue(buffer, &meta, elem, level + 1);

        len = JBE_OFFLENFLD(meta);
        totallen += len;

        /*
         * Bail out if total variable-length data exceeds what will fit in a
         * JEntry length field.  We check this in each iteration, not just
         * once at the end, to forestall possible integer overflow.
         */
        if (totallen > JENTRY_OFFLENMASK)
            ereport(ERROR,
                    (errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
                     errmsg("total size of jsonb array elements exceeds the maximum of %u bytes",
                            JENTRY_OFFLENMASK)));

        /*
         * Convert each JB_OFFSET_STRIDE'th length to an offset.
         */
        if ((i % JB_OFFSET_STRIDE) == 0)
            meta = (meta & JENTRY_TYPEMASK) | totallen | JENTRY_HAS_OFF;

        copyToBuffer(buffer, jentry_offset, (char *) &meta, sizeof(JEntry));
        jentry_offset += sizeof(JEntry);
    }

    /* Total data size is everything we've appended to buffer */
    totallen = buffer->len - base_offset;

    /* Check length again, since we didn't include the metadata above */
    if (totallen > JENTRY_OFFLENMASK)
        ereport(ERROR,
                (errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
                 errmsg("total size of jsonb array elements exceeds the maximum of %u bytes",
                        JENTRY_OFFLENMASK)));

    /* Initialize the header of this node in the container's JEntry array */
    *pheader = JENTRY_ISCONTAINER | totallen;
}

static void
convertJsonbObject(StringInfo buffer, JEntry *pheader, JsonbValue *val, int level)
{
    int         base_offset;
    int         jentry_offset;
    int         i;
    int         totallen;
    uint32      header;
    int         nPairs = val->val.object.nPairs;

    /* Remember where in the buffer this object starts. */
    base_offset = buffer->len;

    /* Align to 4-byte boundary (any padding counts as part of my data) */
    padBufferToInt(buffer);

    /*
     * Construct the header Jentry and store it in the beginning of the
     * variable-length payload.
     */
    header = nPairs | JB_FOBJECT;
    appendToBuffer(buffer, (char *) &header, sizeof(uint32));

    /* Reserve space for the JEntries of the keys and values. */
    jentry_offset = reserveFromBuffer(buffer, sizeof(JEntry) * nPairs * 2);

    /*
     * Iterate over the keys, then over the values, since that is the ordering
     * we want in the on-disk representation.
     */
    totallen = 0;
    for (i = 0; i < nPairs; i++)
    {
        JsonbPair  *pair = &val->val.object.pairs[i];
        int         len;
        JEntry      meta;

        /*
         * Convert key, producing a JEntry and appending its variable-length
         * data to buffer
         */
        convertJsonbScalar(buffer, &meta, &pair->key);

        len = JBE_OFFLENFLD(meta);
        totallen += len;

        /*
         * Bail out if total variable-length data exceeds what will fit in a
         * JEntry length field.  We check this in each iteration, not just
         * once at the end, to forestall possible integer overflow.
         */
        if (totallen > JENTRY_OFFLENMASK)
            ereport(ERROR,
                    (errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
                     errmsg("total size of jsonb object elements exceeds the maximum of %u bytes",
                            JENTRY_OFFLENMASK)));

        /*
         * Convert each JB_OFFSET_STRIDE'th length to an offset.
         */
        if ((i % JB_OFFSET_STRIDE) == 0)
            meta = (meta & JENTRY_TYPEMASK) | totallen | JENTRY_HAS_OFF;

        copyToBuffer(buffer, jentry_offset, (char *) &meta, sizeof(JEntry));
        jentry_offset += sizeof(JEntry);
    }
    for (i = 0; i < nPairs; i++)
    {
        JsonbPair  *pair = &val->val.object.pairs[i];
        int         len;
        JEntry      meta;

        /*
         * Convert value, producing a JEntry and appending its variable-length
         * data to buffer
         */
        convertJsonbValue(buffer, &meta, &pair->value, level + 1);

        len = JBE_OFFLENFLD(meta);
        totallen += len;

        /*
         * Bail out if total variable-length data exceeds what will fit in a
         * JEntry length field.  We check this in each iteration, not just
         * once at the end, to forestall possible integer overflow.
         */
        if (totallen > JENTRY_OFFLENMASK)
            ereport(ERROR,
                    (errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
                     errmsg("total size of jsonb object elements exceeds the maximum of %u bytes",
                            JENTRY_OFFLENMASK)));

        /*
         * Convert each JB_OFFSET_STRIDE'th length to an offset.
         */
        if (((i + nPairs) % JB_OFFSET_STRIDE) == 0)
            meta = (meta & JENTRY_TYPEMASK) | totallen | JENTRY_HAS_OFF;

        copyToBuffer(buffer, jentry_offset, (char *) &meta, sizeof(JEntry));
        jentry_offset += sizeof(JEntry);
    }

    /* Total data size is everything we've appended to buffer */
    totallen = buffer->len - base_offset;

    /* Check length again, since we didn't include the metadata above */
    if (totallen > JENTRY_OFFLENMASK)
        ereport(ERROR,
                (errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED),
                 errmsg("total size of jsonb object elements exceeds the maximum of %u bytes",
                        JENTRY_OFFLENMASK)));

    /* Initialize the header of this node in the container's JEntry array */
    *pheader = JENTRY_ISCONTAINER | totallen;
}

static void
convertJsonbScalar(StringInfo buffer, JEntry *jentry, JsonbValue *scalarVal)
{
    int         numlen;
    short       padlen;

    switch (scalarVal->type)
    {
        case jbvNull:
            *jentry = JENTRY_ISNULL;
            break;

        case jbvString:
            appendToBuffer(buffer, scalarVal->val.string.val, scalarVal->val.string.len);

            *jentry = scalarVal->val.string.len;
            break;

        case jbvNumeric:
            numlen = VARSIZE_ANY(scalarVal->val.numeric);
            padlen = padBufferToInt(buffer);

            appendToBuffer(buffer, (char *) scalarVal->val.numeric, numlen);

            *jentry = JENTRY_ISNUMERIC | (padlen + numlen);
            break;

        case jbvBool:
            *jentry = (scalarVal->val.boolean) ?
                JENTRY_ISBOOL_TRUE : JENTRY_ISBOOL_FALSE;
            break;

        default:
            elog(ERROR, "invalid jsonb scalar type");
    }
}

/*
 * Compare two jbvString JsonbValue values, a and b.
 *
 * This is a special qsort() comparator used to sort strings in certain
 * internal contexts where it is sufficient to have a well-defined sort order.
 * In particular, object pair keys are sorted according to this criteria to
 * facilitate cheap binary searches where we don't care about lexical sort
 * order.
 *
 * a and b are first sorted based on their length.  If a tie-breaker is
 * required, only then do we consider string binary equality.
 */
static int
lengthCompareJsonbStringValue(const void *a, const void *b)
{
    const JsonbValue *va = (const JsonbValue *) a;
    const JsonbValue *vb = (const JsonbValue *) b;
    int         res;

    Assert(va->type == jbvString);
    Assert(vb->type == jbvString);

    if (va->val.string.len == vb->val.string.len)
    {
        res = memcmp(va->val.string.val, vb->val.string.val, va->val.string.len);
    }
    else
    {
        res = (va->val.string.len > vb->val.string.len) ? 1 : -1;
    }

    return res;
}

/*
 * qsort_arg() comparator to compare JsonbPair values.
 *
 * Third argument 'binequal' may point to a bool. If it's set, *binequal is set
 * to true iff a and b have full binary equality, since some callers have an
 * interest in whether the two values are equal or merely equivalent.
 *
 * N.B: String comparisons here are "length-wise"
 *
 * Pairs with equals keys are ordered such that the order field is respected.
 */
static int
lengthCompareJsonbPair(const void *a, const void *b, void *binequal)
{
    const JsonbPair *pa = (const JsonbPair *) a;
    const JsonbPair *pb = (const JsonbPair *) b;
    int         res;

    res = lengthCompareJsonbStringValue(&pa->key, &pb->key);
    if (res == 0 && binequal)
        *((bool *) binequal) = true;

    /*
     * Guarantee keeping order of equal pair.  Unique algorithm will prefer
     * first element as value.
     */
    if (res == 0)
        res = (pa->order > pb->order) ? -1 : 1;

    return res;
}

/*
 * Sort and unique-ify pairs in JsonbValue object
 */
static void
uniqueifyJsonbObject(JsonbValue *object)
{
    bool        hasNonUniq = false;

    Assert(object->type == jbvObject);

    if (object->val.object.nPairs > 1)
        qsort_arg(object->val.object.pairs, object->val.object.nPairs, sizeof(JsonbPair),
                  lengthCompareJsonbPair, &hasNonUniq);

    if (hasNonUniq)
    {
        JsonbPair  *ptr = object->val.object.pairs + 1,
                   *res = object->val.object.pairs;

        while (ptr - object->val.object.pairs < object->val.object.nPairs)
        {
            /* Avoid copying over duplicate */
            if (lengthCompareJsonbStringValue(ptr, res) != 0)
            {
                res++;
                if (ptr != res)
                    memcpy(res, ptr, sizeof(JsonbPair));
            }
            ptr++;
        }

        object->val.object.nPairs = res + 1 - object->val.object.pairs;
    }
}