jsonpath_exec.c

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/*-------------------------------------------------------------------------
 *
 * jsonpath_exec.c
 *   Routines for SQL/JSON path execution.
 *
 * Jsonpath is executed in the global context stored in JsonPathExecContext,
 * which is passed to almost every function involved into execution.  Entry
 * point for jsonpath execution is executeJsonPath() function, which
 * initializes execution context including initial JsonPathItem and JsonbValue,
 * flags, stack for calculation of @ in filters.
 *
 * The result of jsonpath query execution is enum JsonPathExecResult and
 * if succeeded sequence of JsonbValue, written to JsonValueList *found, which
 * is passed through the jsonpath items.  When found == NULL, we're inside
 * exists-query and we're interested only in whether result is empty.  In this
 * case execution is stopped once first result item is found, and the only
 * execution result is JsonPathExecResult.  The values of JsonPathExecResult
 * are following:
 * - jperOk         -- result sequence is not empty
 * - jperNotFound   -- result sequence is empty
 * - jperError      -- error occurred during execution
 *
 * Jsonpath is executed recursively (see executeItem()) starting form the
 * first path item (which in turn might be, for instance, an arithmetic
 * expression evaluated separately).  On each step single JsonbValue obtained
 * from previous path item is processed.  The result of processing is a
 * sequence of JsonbValue (probably empty), which is passed to the next path
 * item one by one.  When there is no next path item, then JsonbValue is added
 * to the 'found' list.  When found == NULL, then execution functions just
 * return jperOk (see executeNextItem()).
 *
 * Many of jsonpath operations require automatic unwrapping of arrays in lax
 * mode.  So, if input value is array, then corresponding operation is
 * processed not on array itself, but on all of its members one by one.
 * executeItemOptUnwrapTarget() function have 'unwrap' argument, which indicates
 * whether unwrapping of array is needed.  When unwrap == true, each of array
 * members is passed to executeItemOptUnwrapTarget() again but with unwrap == false
 * in order to evade subsequent array unwrapping.
 *
 * All boolean expressions (predicates) are evaluated by executeBoolItem()
 * function, which returns tri-state JsonPathBool.  When error is occurred
 * during predicate execution, it returns jpbUnknown.  According to standard
 * predicates can be only inside filters.  But we support their usage as
 * jsonpath expression.  This helps us to implement @@ operator.  In this case
 * resulting JsonPathBool is transformed into jsonb bool or null.
 *
 * Arithmetic and boolean expression are evaluated recursively from expression
 * tree top down to the leaves.  Therefore, for binary arithmetic expressions
 * we calculate operands first.  Then we check that results are numeric
 * singleton lists, calculate the result and pass it to the next path item.
 *
 * Copyright (c) 2019, PostgreSQL Global Development Group
 *
 * IDENTIFICATION
 *  src/backend/utils/adt/jsonpath_exec.c
 *
 *-------------------------------------------------------------------------
 */

#include "postgres.h"

#include "catalog/pg_collation.h"
#include "catalog/pg_type.h"
#include "funcapi.h"
#include "lib/stringinfo.h"
#include "miscadmin.h"
#include "regex/regex.h"
#include "utils/builtins.h"
#include "utils/datum.h"
#include "utils/formatting.h"
#include "utils/float.h"
#include "utils/guc.h"
#include "utils/json.h"
#include "utils/jsonpath.h"
#include "utils/date.h"
#include "utils/timestamp.h"
#include "utils/varlena.h"


/*
 * Represents "base object" and it's "id" for .keyvalue() evaluation.
 */
typedef struct JsonBaseObjectInfo
{
    JsonbContainer *jbc;
    int         id;
} JsonBaseObjectInfo;

/*
 * Context of jsonpath execution.
 */
typedef struct JsonPathExecContext
{
    Jsonb      *vars;           /* variables to substitute into jsonpath */
    JsonbValue *root;           /* for $ evaluation */
    JsonbValue *current;        /* for @ evaluation */
    JsonBaseObjectInfo baseObject;  /* "base object" for .keyvalue()
                                     * evaluation */
    int         lastGeneratedObjectId;  /* "id" counter for .keyvalue()
                                         * evaluation */
    int         innermostArraySize; /* for LAST array index evaluation */
    bool        laxMode;        /* true for "lax" mode, false for "strict"
                                 * mode */
    bool        ignoreStructuralErrors; /* with "true" structural errors such
                                         * as absence of required json item or
                                         * unexpected json item type are
                                         * ignored */
    bool        throwErrors;    /* with "false" all suppressible errors are
                                 * suppressed */
} JsonPathExecContext;

/* Context for LIKE_REGEX execution. */
typedef struct JsonLikeRegexContext
{
    text       *regex;
    int         cflags;
} JsonLikeRegexContext;

/* Result of jsonpath predicate evaluation */
typedef enum JsonPathBool
{
    jpbFalse = 0,
    jpbTrue = 1,
    jpbUnknown = 2
} JsonPathBool;

/* Result of jsonpath expression evaluation */
typedef enum JsonPathExecResult
{
    jperOk = 0,
    jperNotFound = 1,
    jperError = 2
} JsonPathExecResult;

#define jperIsError(jper)           ((jper) == jperError)

/*
 * List of jsonb values with shortcut for single-value list.
 */
typedef struct JsonValueList
{
    JsonbValue *singleton;
    List       *list;
} JsonValueList;

typedef struct JsonValueListIterator
{
    JsonbValue *value;
    List       *list;
    ListCell   *next;
} JsonValueListIterator;

/* strict/lax flags is decomposed into four [un]wrap/error flags */
#define jspStrictAbsenseOfErrors(cxt)   (!(cxt)->laxMode)
#define jspAutoUnwrap(cxt)              ((cxt)->laxMode)
#define jspAutoWrap(cxt)                ((cxt)->laxMode)
#define jspIgnoreStructuralErrors(cxt)  ((cxt)->ignoreStructuralErrors)
#define jspThrowErrors(cxt)             ((cxt)->throwErrors)

/* Convenience macro: return or throw error depending on context */
#define RETURN_ERROR(throw_error) \
do { \
    if (jspThrowErrors(cxt)) \
        throw_error; \
    else \
        return jperError; \
} while (0)

typedef JsonPathBool (*JsonPathPredicateCallback) (JsonPathItem *jsp,
                                                   JsonbValue *larg,
                                                   JsonbValue *rarg,
                                                   void *param);
typedef Numeric (*BinaryArithmFunc) (Numeric num1, Numeric num2, bool *error);

static JsonPathExecResult executeJsonPath(JsonPath *path, Jsonb *vars,
                                          Jsonb *json, bool throwErrors, JsonValueList *result);
static JsonPathExecResult executeItem(JsonPathExecContext *cxt,
                                      JsonPathItem *jsp, JsonbValue *jb, JsonValueList *found);
static JsonPathExecResult executeItemOptUnwrapTarget(JsonPathExecContext *cxt,
                                                     JsonPathItem *jsp, JsonbValue *jb,
                                                     JsonValueList *found, bool unwrap);
static JsonPathExecResult executeItemUnwrapTargetArray(JsonPathExecContext *cxt,
                                                       JsonPathItem *jsp, JsonbValue *jb,
                                                       JsonValueList *found, bool unwrapElements);
static JsonPathExecResult executeNextItem(JsonPathExecContext *cxt,
                                          JsonPathItem *cur, JsonPathItem *next,
                                          JsonbValue *v, JsonValueList *found, bool copy);
static JsonPathExecResult executeItemOptUnwrapResult(JsonPathExecContext *cxt, JsonPathItem *jsp, JsonbValue *jb,
                                                     bool unwrap, JsonValueList *found);
static JsonPathExecResult executeItemOptUnwrapResultNoThrow(JsonPathExecContext *cxt, JsonPathItem *jsp,
                                                            JsonbValue *jb, bool unwrap, JsonValueList *found);
static JsonPathBool executeBoolItem(JsonPathExecContext *cxt,
                                    JsonPathItem *jsp, JsonbValue *jb, bool canHaveNext);
static JsonPathBool executeNestedBoolItem(JsonPathExecContext *cxt,
                                          JsonPathItem *jsp, JsonbValue *jb);
static JsonPathExecResult executeAnyItem(JsonPathExecContext *cxt,
                                         JsonPathItem *jsp, JsonbContainer *jbc, JsonValueList *found,
                                         uint32 level, uint32 first, uint32 last,
                                         bool ignoreStructuralErrors, bool unwrapNext);
static JsonPathBool executePredicate(JsonPathExecContext *cxt,
                                     JsonPathItem *pred, JsonPathItem *larg, JsonPathItem *rarg,
                                     JsonbValue *jb, bool unwrapRightArg,
                                     JsonPathPredicateCallback exec, void *param);
static JsonPathExecResult executeBinaryArithmExpr(JsonPathExecContext *cxt,
                                                  JsonPathItem *jsp, JsonbValue *jb,
                                                  BinaryArithmFunc func, JsonValueList *found);
static JsonPathExecResult executeUnaryArithmExpr(JsonPathExecContext *cxt,
                                                 JsonPathItem *jsp, JsonbValue *jb, PGFunction func,
                                                 JsonValueList *found);
static JsonPathBool executeStartsWith(JsonPathItem *jsp,
                                      JsonbValue *whole, JsonbValue *initial, void *param);
static JsonPathBool executeLikeRegex(JsonPathItem *jsp, JsonbValue *str,
                                     JsonbValue *rarg, void *param);
static JsonPathExecResult executeNumericItemMethod(JsonPathExecContext *cxt,
                                                   JsonPathItem *jsp, JsonbValue *jb, bool unwrap, PGFunction func,
                                                   JsonValueList *found);
static JsonPathExecResult executeKeyValueMethod(JsonPathExecContext *cxt,
                                                JsonPathItem *jsp, JsonbValue *jb, JsonValueList *found);
static JsonPathExecResult appendBoolResult(JsonPathExecContext *cxt,
                                           JsonPathItem *jsp, JsonValueList *found, JsonPathBool res);
static void getJsonPathItem(JsonPathExecContext *cxt, JsonPathItem *item,
                            JsonbValue *value);
static void getJsonPathVariable(JsonPathExecContext *cxt,
                                JsonPathItem *variable, Jsonb *vars, JsonbValue *value);
static int  JsonbArraySize(JsonbValue *jb);
static JsonPathBool executeComparison(JsonPathItem *cmp, JsonbValue *lv,
                                      JsonbValue *rv, void *p);
static JsonPathBool compareItems(int32 op, JsonbValue *jb1, JsonbValue *jb2);
static int  compareNumeric(Numeric a, Numeric b);
static JsonbValue *copyJsonbValue(JsonbValue *src);
static JsonPathExecResult getArrayIndex(JsonPathExecContext *cxt,
                                        JsonPathItem *jsp, JsonbValue *jb, int32 *index);
static JsonBaseObjectInfo setBaseObject(JsonPathExecContext *cxt,
                                        JsonbValue *jbv, int32 id);
static void JsonValueListAppend(JsonValueList *jvl, JsonbValue *jbv);
static int  JsonValueListLength(const JsonValueList *jvl);
static bool JsonValueListIsEmpty(JsonValueList *jvl);
static JsonbValue *JsonValueListHead(JsonValueList *jvl);
static List *JsonValueListGetList(JsonValueList *jvl);
static void JsonValueListInitIterator(const JsonValueList *jvl,
                                      JsonValueListIterator *it);
static JsonbValue *JsonValueListNext(const JsonValueList *jvl,
                                     JsonValueListIterator *it);
static int  JsonbType(JsonbValue *jb);
static JsonbValue *JsonbInitBinary(JsonbValue *jbv, Jsonb *jb);
static int  JsonbType(JsonbValue *jb);
static JsonbValue *getScalar(JsonbValue *scalar, enum jbvType type);
static JsonbValue *wrapItemsInArray(const JsonValueList *items);

/****************** User interface to JsonPath executor ********************/

/*
 * jsonb_path_exists
 *      Returns true if jsonpath returns at least one item for the specified
 *      jsonb value.  This function and jsonb_path_match() are used to
 *      implement @? and @@ operators, which in turn are intended to have an
 *      index support.  Thus, it's desirable to make it easier to achieve
 *      consistency between index scan results and sequential scan results.
 *      So, we throw as less errors as possible.  Regarding this function,
 *      such behavior also matches behavior of JSON_EXISTS() clause of
 *      SQL/JSON.  Regarding jsonb_path_match(), this function doesn't have
 *      an analogy in SQL/JSON, so we define its behavior on our own.
 */
Datum
jsonb_path_exists(PG_FUNCTION_ARGS)
{
    Jsonb      *jb = PG_GETARG_JSONB_P(0);
    JsonPath   *jp = PG_GETARG_JSONPATH_P(1);
    JsonPathExecResult res;
    Jsonb      *vars = NULL;
    bool        silent = true;

    if (PG_NARGS() == 4)
    {
        vars = PG_GETARG_JSONB_P(2);
        silent = PG_GETARG_BOOL(3);
    }

    res = executeJsonPath(jp, vars, jb, !silent, NULL);

    PG_FREE_IF_COPY(jb, 0);
    PG_FREE_IF_COPY(jp, 1);

    if (jperIsError(res))
        PG_RETURN_NULL();

    PG_RETURN_BOOL(res == jperOk);
}

/*
 * jsonb_path_exists_opr
 *      Implementation of operator "jsonb @? jsonpath" (2-argument version of
 *      jsonb_path_exists()).
 */
Datum
jsonb_path_exists_opr(PG_FUNCTION_ARGS)
{
    /* just call the other one -- it can handle both cases */
    return jsonb_path_exists(fcinfo);
}

/*
 * jsonb_path_match
 *      Returns jsonpath predicate result item for the specified jsonb value.
 *      See jsonb_path_exists() comment for details regarding error handling.
 */
Datum
jsonb_path_match(PG_FUNCTION_ARGS)
{
    Jsonb      *jb = PG_GETARG_JSONB_P(0);
    JsonPath   *jp = PG_GETARG_JSONPATH_P(1);
    JsonValueList found = {0};
    Jsonb      *vars = NULL;
    bool        silent = true;

    if (PG_NARGS() == 4)
    {
        vars = PG_GETARG_JSONB_P(2);
        silent = PG_GETARG_BOOL(3);
    }

    (void) executeJsonPath(jp, vars, jb, !silent, &found);

    PG_FREE_IF_COPY(jb, 0);
    PG_FREE_IF_COPY(jp, 1);

    if (JsonValueListLength(&found) == 1)
    {
        JsonbValue *jbv = JsonValueListHead(&found);

        if (jbv->type == jbvBool)
            PG_RETURN_BOOL(jbv->val.boolean);

        if (jbv->type == jbvNull)
            PG_RETURN_NULL();
    }

    if (!silent)
        ereport(ERROR,
                (errcode(ERRCODE_SINGLETON_JSON_ITEM_REQUIRED),
                 errmsg("single boolean result is expected")));

    PG_RETURN_NULL();
}

/*
 * jsonb_path_match_opr
 *      Implementation of operator "jsonb @@ jsonpath" (2-argument version of
 *      jsonb_path_match()).
 */
Datum
jsonb_path_match_opr(PG_FUNCTION_ARGS)
{
    /* just call the other one -- it can handle both cases */
    return jsonb_path_match(fcinfo);
}

/*
 * jsonb_path_query
 *      Executes jsonpath for given jsonb document and returns result as
 *      rowset.
 */
Datum
jsonb_path_query(PG_FUNCTION_ARGS)
{
    FuncCallContext *funcctx;
    List       *found;
    JsonbValue *v;
    ListCell   *c;

    if (SRF_IS_FIRSTCALL())
    {
        JsonPath   *jp;
        Jsonb      *jb;
        MemoryContext oldcontext;
        Jsonb      *vars;
        bool        silent;
        JsonValueList found = {0};

        funcctx = SRF_FIRSTCALL_INIT();
        oldcontext = MemoryContextSwitchTo(funcctx->multi_call_memory_ctx);

        jb = PG_GETARG_JSONB_P_COPY(0);
        jp = PG_GETARG_JSONPATH_P_COPY(1);
        vars = PG_GETARG_JSONB_P_COPY(2);
        silent = PG_GETARG_BOOL(3);

        (void) executeJsonPath(jp, vars, jb, !silent, &found);

        funcctx->user_fctx = JsonValueListGetList(&found);

        MemoryContextSwitchTo(oldcontext);
    }

    funcctx = SRF_PERCALL_SETUP();
    found = funcctx->user_fctx;

    c = list_head(found);

    if (c == NULL)
        SRF_RETURN_DONE(funcctx);

    v = lfirst(c);
    funcctx->user_fctx = list_delete_first(found);

    SRF_RETURN_NEXT(funcctx, JsonbPGetDatum(JsonbValueToJsonb(v)));
}

/*
 * jsonb_path_query_array
 *      Executes jsonpath for given jsonb document and returns result as
 *      jsonb array.
 */
Datum
jsonb_path_query_array(PG_FUNCTION_ARGS)
{
    Jsonb      *jb = PG_GETARG_JSONB_P(0);
    JsonPath   *jp = PG_GETARG_JSONPATH_P(1);
    JsonValueList found = {0};
    Jsonb      *vars = PG_GETARG_JSONB_P(2);
    bool        silent = PG_GETARG_BOOL(3);

    (void) executeJsonPath(jp, vars, jb, !silent, &found);

    PG_RETURN_JSONB_P(JsonbValueToJsonb(wrapItemsInArray(&found)));
}

/*
 * jsonb_path_query_first
 *      Executes jsonpath for given jsonb document and returns first result
 *      item.  If there are no items, NULL returned.
 */
Datum
jsonb_path_query_first(PG_FUNCTION_ARGS)
{
    Jsonb      *jb = PG_GETARG_JSONB_P(0);
    JsonPath   *jp = PG_GETARG_JSONPATH_P(1);
    JsonValueList found = {0};
    Jsonb      *vars = PG_GETARG_JSONB_P(2);
    bool        silent = PG_GETARG_BOOL(3);

    (void) executeJsonPath(jp, vars, jb, !silent, &found);

    if (JsonValueListLength(&found) >= 1)
        PG_RETURN_JSONB_P(JsonbValueToJsonb(JsonValueListHead(&found)));
    else
        PG_RETURN_NULL();
}

/********************Execute functions for JsonPath**************************/

/*
 * Interface to jsonpath executor
 *
 * 'path' - jsonpath to be executed
 * 'vars' - variables to be substituted to jsonpath
 * 'json' - target document for jsonpath evaluation
 * 'throwErrors' - whether we should throw suppressible errors
 * 'result' - list to store result items into
 *
 * Returns an error if a recoverable error happens during processing, or NULL
 * on no error.
 *
 * Note, jsonb and jsonpath values should be available and untoasted during
 * work because JsonPathItem, JsonbValue and result item could have pointers
 * into input values.  If caller needs to just check if document matches
 * jsonpath, then it doesn't provide a result arg.  In this case executor
 * works till first positive result and does not check the rest if possible.
 * In other case it tries to find all the satisfied result items.
 */
static JsonPathExecResult
executeJsonPath(JsonPath *path, Jsonb *vars, Jsonb *json, bool throwErrors,
                JsonValueList *result)
{
    JsonPathExecContext cxt;
    JsonPathExecResult res;
    JsonPathItem jsp;
    JsonbValue  jbv;

    jspInit(&jsp, path);

    if (!JsonbExtractScalar(&json->root, &jbv))
        JsonbInitBinary(&jbv, json);

    if (vars && !JsonContainerIsObject(&vars->root))
    {
        ereport(ERROR,
                (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                 errmsg("\"vars\" argument is not an object"),
                 errdetail("Jsonpath parameters should be encoded as key-value pairs of \"vars\" object.")));
    }

    cxt.vars = vars;
    cxt.laxMode = (path->header & JSONPATH_LAX) != 0;
    cxt.ignoreStructuralErrors = cxt.laxMode;
    cxt.root = &jbv;
    cxt.current = &jbv;
    cxt.baseObject.jbc = NULL;
    cxt.baseObject.id = 0;
    cxt.lastGeneratedObjectId = vars ? 2 : 1;
    cxt.innermostArraySize = -1;
    cxt.throwErrors = throwErrors;

    if (jspStrictAbsenseOfErrors(&cxt) && !result)
    {
        /*
         * In strict mode we must get a complete list of values to check that
         * there are no errors at all.
         */
        JsonValueList vals = {0};

        res = executeItem(&cxt, &jsp, &jbv, &vals);

        if (jperIsError(res))
            return res;

        return JsonValueListIsEmpty(&vals) ? jperNotFound : jperOk;
    }

    res = executeItem(&cxt, &jsp, &jbv, result);

    Assert(!throwErrors || !jperIsError(res));

    return res;
}

/*
 * Execute jsonpath with automatic unwrapping of current item in lax mode.
 */
static JsonPathExecResult
executeItem(JsonPathExecContext *cxt, JsonPathItem *jsp,
            JsonbValue *jb, JsonValueList *found)
{
    return executeItemOptUnwrapTarget(cxt, jsp, jb, found, jspAutoUnwrap(cxt));
}

/*
 * Main jsonpath executor function: walks on jsonpath structure, finds
 * relevant parts of jsonb and evaluates expressions over them.
 * When 'unwrap' is true current SQL/JSON item is unwrapped if it is an array.
 */
static JsonPathExecResult
executeItemOptUnwrapTarget(JsonPathExecContext *cxt, JsonPathItem *jsp,
                           JsonbValue *jb, JsonValueList *found, bool unwrap)
{
    JsonPathItem elem;
    JsonPathExecResult res = jperNotFound;
    JsonBaseObjectInfo baseObject;

    check_stack_depth();
    CHECK_FOR_INTERRUPTS();

    switch (jsp->type)
    {
            /* all boolean item types: */
        case jpiAnd:
        case jpiOr:
        case jpiNot:
        case jpiIsUnknown:
        case jpiEqual:
        case jpiNotEqual:
        case jpiLess:
        case jpiGreater:
        case jpiLessOrEqual:
        case jpiGreaterOrEqual:
        case jpiExists:
        case jpiStartsWith:
        case jpiLikeRegex:
            {
                JsonPathBool st = executeBoolItem(cxt, jsp, jb, true);

                res = appendBoolResult(cxt, jsp, found, st);
                break;
            }

        case jpiKey:
            if (JsonbType(jb) == jbvObject)
            {
                JsonbValue *v;
                JsonbValue  key;

                key.type = jbvString;
                key.val.string.val = jspGetString(jsp, &key.val.string.len);

                v = findJsonbValueFromContainer(jb->val.binary.data,
                                                JB_FOBJECT, &key);

                if (v != NULL)
                {
                    res = executeNextItem(cxt, jsp, NULL,
                                          v, found, false);

                    /* free value if it was not added to found list */
                    if (jspHasNext(jsp) || !found)
                        pfree(v);
                }
                else if (!jspIgnoreStructuralErrors(cxt))
                {
                    Assert(found);

                    if (!jspThrowErrors(cxt))
                        return jperError;

                    ereport(ERROR,
                            (errcode(ERRCODE_JSON_MEMBER_NOT_FOUND), \
                             errmsg("JSON object does not contain key \"%s\"",
                                    pnstrdup(key.val.string.val,
                                             key.val.string.len))));
                }
            }
            else if (unwrap && JsonbType(jb) == jbvArray)
                return executeItemUnwrapTargetArray(cxt, jsp, jb, found, false);
            else if (!jspIgnoreStructuralErrors(cxt))
            {
                Assert(found);
                RETURN_ERROR(ereport(ERROR,
                                     (errcode(ERRCODE_JSON_MEMBER_NOT_FOUND),
                                      errmsg("jsonpath member accessor can only be applied to an object"))));
            }
            break;

        case jpiRoot:
            jb = cxt->root;
            baseObject = setBaseObject(cxt, jb, 0);
            res = executeNextItem(cxt, jsp, NULL, jb, found, true);
            cxt->baseObject = baseObject;
            break;

        case jpiCurrent:
            res = executeNextItem(cxt, jsp, NULL, cxt->current,
                                  found, true);
            break;

        case jpiAnyArray:
            if (JsonbType(jb) == jbvArray)
            {
                bool        hasNext = jspGetNext(jsp, &elem);

                res = executeItemUnwrapTargetArray(cxt, hasNext ? &elem : NULL,
                                                   jb, found, jspAutoUnwrap(cxt));
            }
            else if (jspAutoWrap(cxt))
                res = executeNextItem(cxt, jsp, NULL, jb, found, true);
            else if (!jspIgnoreStructuralErrors(cxt))
                RETURN_ERROR(ereport(ERROR,
                                     (errcode(ERRCODE_JSON_ARRAY_NOT_FOUND),
                                      errmsg("jsonpath wildcard array accessor can only be applied to an array"))));
            break;

        case jpiIndexArray:
            if (JsonbType(jb) == jbvArray || jspAutoWrap(cxt))
            {
                int         innermostArraySize = cxt->innermostArraySize;
                int         i;
                int         size = JsonbArraySize(jb);
                bool        singleton = size < 0;
                bool        hasNext = jspGetNext(jsp, &elem);

                if (singleton)
                    size = 1;

                cxt->innermostArraySize = size; /* for LAST evaluation */

                for (i = 0; i < jsp->content.array.nelems; i++)
                {
                    JsonPathItem from;
                    JsonPathItem to;
                    int32       index;
                    int32       index_from;
                    int32       index_to;
                    bool        range = jspGetArraySubscript(jsp, &from,
                                                             &to, i);

                    res = getArrayIndex(cxt, &from, jb, &index_from);

                    if (jperIsError(res))
                        break;

                    if (range)
                    {
                        res = getArrayIndex(cxt, &to, jb, &index_to);

                        if (jperIsError(res))
                            break;
                    }
                    else
                        index_to = index_from;

                    if (!jspIgnoreStructuralErrors(cxt) &&
                        (index_from < 0 ||
                         index_from > index_to ||
                         index_to >= size))
                        RETURN_ERROR(ereport(ERROR,
                                             (errcode(ERRCODE_INVALID_JSON_SUBSCRIPT),
                                              errmsg("jsonpath array subscript is out of bounds"))));

                    if (index_from < 0)
                        index_from = 0;

                    if (index_to >= size)
                        index_to = size - 1;

                    res = jperNotFound;

                    for (index = index_from; index <= index_to; index++)
                    {
                        JsonbValue *v;
                        bool        copy;

                        if (singleton)
                        {
                            v = jb;
                            copy = true;
                        }
                        else
                        {
                            v = getIthJsonbValueFromContainer(jb->val.binary.data,
                                                              (uint32) index);

                            if (v == NULL)
                                continue;

                            copy = false;
                        }

                        if (!hasNext && !found)
                            return jperOk;

                        res = executeNextItem(cxt, jsp, &elem, v, found,
                                              copy);

                        if (jperIsError(res))
                            break;

                        if (res == jperOk && !found)
                            break;
                    }

                    if (jperIsError(res))
                        break;

                    if (res == jperOk && !found)
                        break;
                }

                cxt->innermostArraySize = innermostArraySize;
            }
            else if (!jspIgnoreStructuralErrors(cxt))
            {
                RETURN_ERROR(ereport(ERROR,
                                     (errcode(ERRCODE_JSON_ARRAY_NOT_FOUND),
                                      errmsg("jsonpath array accessor can only be applied to an array"))));
            }
            break;

        case jpiLast:
            {
                JsonbValue  tmpjbv;
                JsonbValue *lastjbv;
                int         last;
                bool        hasNext = jspGetNext(jsp, &elem);

                if (cxt->innermostArraySize < 0)
                    elog(ERROR, "evaluating jsonpath LAST outside of array subscript");

                if (!hasNext && !found)
                {
                    res = jperOk;
                    break;
                }

                last = cxt->innermostArraySize - 1;

                lastjbv = hasNext ? &tmpjbv : palloc(sizeof(*lastjbv));

                lastjbv->type = jbvNumeric;
                lastjbv->val.numeric =
                    DatumGetNumeric(DirectFunctionCall1(int4_numeric,
                                                        Int32GetDatum(last)));

                res = executeNextItem(cxt, jsp, &elem,
                                      lastjbv, found, hasNext);
            }
            break;

        case jpiAnyKey:
            if (JsonbType(jb) == jbvObject)
            {
                bool        hasNext = jspGetNext(jsp, &elem);

                if (jb->type != jbvBinary)
                    elog(ERROR, "invalid jsonb object type: %d", jb->type);

                return executeAnyItem
                    (cxt, hasNext ? &elem : NULL,
                     jb->val.binary.data, found, 1, 1, 1,
                     false, jspAutoUnwrap(cxt));
            }
            else if (unwrap && JsonbType(jb) == jbvArray)
                return executeItemUnwrapTargetArray(cxt, jsp, jb, found, false);
            else if (!jspIgnoreStructuralErrors(cxt))
            {
                Assert(found);
                RETURN_ERROR(ereport(ERROR,
                                     (errcode(ERRCODE_JSON_OBJECT_NOT_FOUND),
                                      errmsg("jsonpath wildcard member accessor can only be applied to an object"))));
            }
            break;

        case jpiAdd:
            return executeBinaryArithmExpr(cxt, jsp, jb,
                                           numeric_add_opt_error, found);

        case jpiSub:
            return executeBinaryArithmExpr(cxt, jsp, jb,
                                           numeric_sub_opt_error, found);

        case jpiMul:
            return executeBinaryArithmExpr(cxt, jsp, jb,
                                           numeric_mul_opt_error, found);

        case jpiDiv:
            return executeBinaryArithmExpr(cxt, jsp, jb,
                                           numeric_div_opt_error, found);

        case jpiMod:
            return executeBinaryArithmExpr(cxt, jsp, jb,
                                           numeric_mod_opt_error, found);

        case jpiPlus:
            return executeUnaryArithmExpr(cxt, jsp, jb, NULL, found);

        case jpiMinus:
            return executeUnaryArithmExpr(cxt, jsp, jb, numeric_uminus,
                                          found);

        case jpiFilter:
            {
                JsonPathBool st;

                if (unwrap && JsonbType(jb) == jbvArray)
                    return executeItemUnwrapTargetArray(cxt, jsp, jb, found,
                                                        false);

                jspGetArg(jsp, &elem);
                st = executeNestedBoolItem(cxt, &elem, jb);
                if (st != jpbTrue)
                    res = jperNotFound;
                else
                    res = executeNextItem(cxt, jsp, NULL,
                                          jb, found, true);
                break;
            }

        case jpiAny:
            {
                bool        hasNext = jspGetNext(jsp, &elem);

                /* first try without any intermediate steps */
                if (jsp->content.anybounds.first == 0)
                {
                    bool        savedIgnoreStructuralErrors;

                    savedIgnoreStructuralErrors = cxt->ignoreStructuralErrors;
                    cxt->ignoreStructuralErrors = true;
                    res = executeNextItem(cxt, jsp, &elem,
                                          jb, found, true);
                    cxt->ignoreStructuralErrors = savedIgnoreStructuralErrors;

                    if (res == jperOk && !found)
                        break;
                }

                if (jb->type == jbvBinary)
                    res = executeAnyItem
                        (cxt, hasNext ? &elem : NULL,
                         jb->val.binary.data, found,
                         1,
                         jsp->content.anybounds.first,
                         jsp->content.anybounds.last,
                         true, jspAutoUnwrap(cxt));
                break;
            }

        case jpiNull:
        case jpiBool:
        case jpiNumeric:
        case jpiString:
        case jpiVariable:
            {
                JsonbValue  vbuf;
                JsonbValue *v;
                bool        hasNext = jspGetNext(jsp, &elem);

                if (!hasNext && !found)
                {
                    res = jperOk;   /* skip evaluation */
                    break;
                }

                v = hasNext ? &vbuf : palloc(sizeof(*v));

                baseObject = cxt->baseObject;
                getJsonPathItem(cxt, jsp, v);

                res = executeNextItem(cxt, jsp, &elem,
                                      v, found, hasNext);
                cxt->baseObject = baseObject;
            }
            break;

        case jpiType:
            {
                JsonbValue *jbv = palloc(sizeof(*jbv));

                jbv->type = jbvString;
                jbv->val.string.val = pstrdup(JsonbTypeName(jb));
                jbv->val.string.len = strlen(jbv->val.string.val);

                res = executeNextItem(cxt, jsp, NULL, jbv,
                                      found, false);
            }
            break;

        case jpiSize:
            {
                int         size = JsonbArraySize(jb);

                if (size < 0)
                {
                    if (!jspAutoWrap(cxt))
                    {
                        if (!jspIgnoreStructuralErrors(cxt))
                            RETURN_ERROR(ereport(ERROR,
                                                 (errcode(ERRCODE_JSON_ARRAY_NOT_FOUND),
                                                  errmsg("jsonpath item method .%s() can only be applied to an array",
                                                         jspOperationName(jsp->type)))));
                        break;
                    }

                    size = 1;
                }

                jb = palloc(sizeof(*jb));

                jb->type = jbvNumeric;
                jb->val.numeric =
                    DatumGetNumeric(DirectFunctionCall1(int4_numeric,
                                                        Int32GetDatum(size)));

                res = executeNextItem(cxt, jsp, NULL, jb, found, false);
            }
            break;

        case jpiAbs:
            return executeNumericItemMethod(cxt, jsp, jb, unwrap, numeric_abs,
                                            found);

        case jpiFloor:
            return executeNumericItemMethod(cxt, jsp, jb, unwrap, numeric_floor,
                                            found);

        case jpiCeiling:
            return executeNumericItemMethod(cxt, jsp, jb, unwrap, numeric_ceil,
                                            found);

        case jpiDouble:
            {
                JsonbValue  jbv;

                if (unwrap && JsonbType(jb) == jbvArray)
                    return executeItemUnwrapTargetArray(cxt, jsp, jb, found,
                                                        false);

                if (jb->type == jbvNumeric)
                {
                    char       *tmp = DatumGetCString(DirectFunctionCall1(numeric_out,
                                                                          NumericGetDatum(jb->val.numeric)));
                    bool        have_error = false;

                    (void) float8in_internal_opt_error(tmp,
                                                       NULL,
                                                       "double precision",
                                                       tmp,
                                                       &have_error);

                    if (have_error)
                        RETURN_ERROR(ereport(ERROR,
                                             (errcode(ERRCODE_NON_NUMERIC_JSON_ITEM),
                                              errmsg("jsonpath item method .%s() can only be applied to a numeric value",
                                                     jspOperationName(jsp->type)))));
                    res = jperOk;
                }
                else if (jb->type == jbvString)
                {
                    /* cast string as double */
                    double      val;
                    char       *tmp = pnstrdup(jb->val.string.val,
                                               jb->val.string.len);
                    bool        have_error = false;

                    val = float8in_internal_opt_error(tmp,
                                                      NULL,
                                                      "double precision",
                                                      tmp,
                                                      &have_error);

                    if (have_error || isinf(val))
                        RETURN_ERROR(ereport(ERROR,
                                             (errcode(ERRCODE_NON_NUMERIC_JSON_ITEM),
                                              errmsg("jsonpath item method .%s() can only be applied to a numeric value",
                                                     jspOperationName(jsp->type)))));

                    jb = &jbv;
                    jb->type = jbvNumeric;
                    jb->val.numeric = DatumGetNumeric(DirectFunctionCall1(float8_numeric,
                                                                          Float8GetDatum(val)));
                    res = jperOk;
                }

                if (res == jperNotFound)
                    RETURN_ERROR(ereport(ERROR,
                                         (errcode(ERRCODE_NON_NUMERIC_JSON_ITEM),
                                          errmsg("jsonpath item method .%s() can only be applied to a string or numeric value",
                                                 jspOperationName(jsp->type)))));

                res = executeNextItem(cxt, jsp, NULL, jb, found, true);
            }
            break;

        case jpiKeyValue:
            if (unwrap && JsonbType(jb) == jbvArray)
                return executeItemUnwrapTargetArray(cxt, jsp, jb, found, false);

            return executeKeyValueMethod(cxt, jsp, jb, found);

        default:
            elog(ERROR, "unrecognized jsonpath item type: %d", jsp->type);
    }

    return res;
}

/*
 * Unwrap current array item and execute jsonpath for each of its elements.
 */
static JsonPathExecResult
executeItemUnwrapTargetArray(JsonPathExecContext *cxt, JsonPathItem *jsp,
                             JsonbValue *jb, JsonValueList *found,
                             bool unwrapElements)
{
    if (jb->type != jbvBinary)
    {
        Assert(jb->type != jbvArray);
        elog(ERROR, "invalid jsonb array value type: %d", jb->type);
    }

    return executeAnyItem
        (cxt, jsp, jb->val.binary.data, found, 1, 1, 1,
         false, unwrapElements);
}

/*
 * Execute next jsonpath item if exists.  Otherwise put "v" to the "found"
 * list if provided.
 */
static JsonPathExecResult
executeNextItem(JsonPathExecContext *cxt,
                JsonPathItem *cur, JsonPathItem *next,
                JsonbValue *v, JsonValueList *found, bool copy)
{
    JsonPathItem elem;
    bool        hasNext;

    if (!cur)
        hasNext = next != NULL;
    else if (next)
        hasNext = jspHasNext(cur);
    else
    {
        next = &elem;
        hasNext = jspGetNext(cur, next);
    }

    if (hasNext)
        return executeItem(cxt, next, v, found);

    if (found)
        JsonValueListAppend(found, copy ? copyJsonbValue(v) : v);

    return jperOk;
}

/*
 * Same as executeItem(), but when "unwrap == true" automatically unwraps
 * each array item from the resulting sequence in lax mode.
 */
static JsonPathExecResult
executeItemOptUnwrapResult(JsonPathExecContext *cxt, JsonPathItem *jsp,
                           JsonbValue *jb, bool unwrap,
                           JsonValueList *found)
{
    if (unwrap && jspAutoUnwrap(cxt))
    {
        JsonValueList seq = {0};
        JsonValueListIterator it;
        JsonPathExecResult res = executeItem(cxt, jsp, jb, &seq);
        JsonbValue *item;

        if (jperIsError(res))
            return res;

        JsonValueListInitIterator(&seq, &it);
        while ((item = JsonValueListNext(&seq, &it)))
        {
            Assert(item->type != jbvArray);

            if (JsonbType(item) == jbvArray)
                executeItemUnwrapTargetArray(cxt, NULL, item, found, false);
            else
                JsonValueListAppend(found, item);
        }

        return jperOk;
    }

    return executeItem(cxt, jsp, jb, found);
}

/*
 * Same as executeItemOptUnwrapResult(), but with error suppression.
 */
static JsonPathExecResult
executeItemOptUnwrapResultNoThrow(JsonPathExecContext *cxt,
                                  JsonPathItem *jsp,
                                  JsonbValue *jb, bool unwrap,
                                  JsonValueList *found)
{
    JsonPathExecResult res;
    bool        throwErrors = cxt->throwErrors;

    cxt->throwErrors = false;
    res = executeItemOptUnwrapResult(cxt, jsp, jb, unwrap, found);
    cxt->throwErrors = throwErrors;

    return res;
}

/* Execute boolean-valued jsonpath expression. */
static JsonPathBool
executeBoolItem(JsonPathExecContext *cxt, JsonPathItem *jsp,
                JsonbValue *jb, bool canHaveNext)
{
    JsonPathItem larg;
    JsonPathItem rarg;
    JsonPathBool res;
    JsonPathBool res2;

    if (!canHaveNext && jspHasNext(jsp))
        elog(ERROR, "boolean jsonpath item cannot have next item");

    switch (jsp->type)
    {
        case jpiAnd:
            jspGetLeftArg(jsp, &larg);
            res = executeBoolItem(cxt, &larg, jb, false);

            if (res == jpbFalse)
                return jpbFalse;

            /*
             * SQL/JSON says that we should check second arg in case of
             * jperError
             */

            jspGetRightArg(jsp, &rarg);
            res2 = executeBoolItem(cxt, &rarg, jb, false);

            return res2 == jpbTrue ? res : res2;

        case jpiOr:
            jspGetLeftArg(jsp, &larg);
            res = executeBoolItem(cxt, &larg, jb, false);

            if (res == jpbTrue)
                return jpbTrue;

            jspGetRightArg(jsp, &rarg);
            res2 = executeBoolItem(cxt, &rarg, jb, false);

            return res2 == jpbFalse ? res : res2;

        case jpiNot:
            jspGetArg(jsp, &larg);

            res = executeBoolItem(cxt, &larg, jb, false);

            if (res == jpbUnknown)
                return jpbUnknown;

            return res == jpbTrue ? jpbFalse : jpbTrue;

        case jpiIsUnknown:
            jspGetArg(jsp, &larg);
            res = executeBoolItem(cxt, &larg, jb, false);
            return res == jpbUnknown ? jpbTrue : jpbFalse;

        case jpiEqual:
        case jpiNotEqual:
        case jpiLess:
        case jpiGreater:
        case jpiLessOrEqual:
        case jpiGreaterOrEqual:
            jspGetLeftArg(jsp, &larg);
            jspGetRightArg(jsp, &rarg);
            return executePredicate(cxt, jsp, &larg, &rarg, jb, true,
                                    executeComparison, NULL);

        case jpiStartsWith:     /* 'whole STARTS WITH initial' */
            jspGetLeftArg(jsp, &larg);  /* 'whole' */
            jspGetRightArg(jsp, &rarg); /* 'initial' */
            return executePredicate(cxt, jsp, &larg, &rarg, jb, false,
                                    executeStartsWith, NULL);

        case jpiLikeRegex:      /* 'expr LIKE_REGEX pattern FLAGS flags' */
            {
                /*
                 * 'expr' is a sequence-returning expression.  'pattern' is a
                 * regex string literal.  SQL/JSON standard requires XQuery
                 * regexes, but we use Postgres regexes here.  'flags' is a
                 * string literal converted to integer flags at compile-time.
                 */
                JsonLikeRegexContext lrcxt = {0};

                jspInitByBuffer(&larg, jsp->base,
                                jsp->content.like_regex.expr);

                return executePredicate(cxt, jsp, &larg, NULL, jb, false,
                                        executeLikeRegex, &lrcxt);
            }

        case jpiExists:
            jspGetArg(jsp, &larg);

            if (jspStrictAbsenseOfErrors(cxt))
            {
                /*
                 * In strict mode we must get a complete list of values to
                 * check that there are no errors at all.
                 */
                JsonValueList vals = {0};
                JsonPathExecResult res =
                executeItemOptUnwrapResultNoThrow(cxt, &larg, jb,
                                                  false, &vals);

                if (jperIsError(res))
                    return jpbUnknown;

                return JsonValueListIsEmpty(&vals) ? jpbFalse : jpbTrue;
            }
            else
            {
                JsonPathExecResult res =
                executeItemOptUnwrapResultNoThrow(cxt, &larg, jb,
                                                  false, NULL);

                if (jperIsError(res))
                    return jpbUnknown;

                return res == jperOk ? jpbTrue : jpbFalse;
            }

        default:
            elog(ERROR, "invalid boolean jsonpath item type: %d", jsp->type);
            return jpbUnknown;
    }
}

/*
 * Execute nested (filters etc.) boolean expression pushing current SQL/JSON
 * item onto the stack.
 */
static JsonPathBool
executeNestedBoolItem(JsonPathExecContext *cxt, JsonPathItem *jsp,
                      JsonbValue *jb)
{
    JsonbValue *prev;
    JsonPathBool res;

    prev = cxt->current;
    cxt->current = jb;
    res = executeBoolItem(cxt, jsp, jb, false);
    cxt->current = prev;

    return res;
}

/*
 * Implementation of several jsonpath nodes:
 *  - jpiAny (.** accessor),
 *  - jpiAnyKey (.* accessor),
 *  - jpiAnyArray ([*] accessor)
 */
static JsonPathExecResult
executeAnyItem(JsonPathExecContext *cxt, JsonPathItem *jsp, JsonbContainer *jbc,
               JsonValueList *found, uint32 level, uint32 first, uint32 last,
               bool ignoreStructuralErrors, bool unwrapNext)
{
    JsonPathExecResult res = jperNotFound;
    JsonbIterator *it;
    int32       r;
    JsonbValue  v;

    check_stack_depth();

    if (level > last)
        return res;

    it = JsonbIteratorInit(jbc);

    /*
     * Recursively iterate over jsonb objects/arrays
     */
    while ((r = JsonbIteratorNext(&it, &v, true)) != WJB_DONE)
    {
        if (r == WJB_KEY)
        {
            r = JsonbIteratorNext(&it, &v, true);
            Assert(r == WJB_VALUE);
        }

        if (r == WJB_VALUE || r == WJB_ELEM)
        {

            if (level >= first ||
                (first == PG_UINT32_MAX && last == PG_UINT32_MAX &&
                 v.type != jbvBinary))  /* leaves only requested */
            {
                /* check expression */
                if (jsp)
                {
                    if (ignoreStructuralErrors)
                    {
                        bool        savedIgnoreStructuralErrors;

                        savedIgnoreStructuralErrors = cxt->ignoreStructuralErrors;
                        cxt->ignoreStructuralErrors = true;
                        res = executeItemOptUnwrapTarget(cxt, jsp, &v, found, unwrapNext);
                        cxt->ignoreStructuralErrors = savedIgnoreStructuralErrors;
                    }
                    else
                        res = executeItemOptUnwrapTarget(cxt, jsp, &v, found, unwrapNext);

                    if (jperIsError(res))
                        break;

                    if (res == jperOk && !found)
                        break;
                }
                else if (found)
                    JsonValueListAppend(found, copyJsonbValue(&v));
                else
                    return jperOk;
            }

            if (level < last && v.type == jbvBinary)
            {
                res = executeAnyItem
                    (cxt, jsp, v.val.binary.data, found,
                     level + 1, first, last,
                     ignoreStructuralErrors, unwrapNext);

                if (jperIsError(res))
                    break;

                if (res == jperOk && found == NULL)
                    break;
            }
        }
    }

    return res;
}

/*
 * Execute unary or binary predicate.
 *
 * Predicates have existence semantics, because their operands are item
 * sequences.  Pairs of items from the left and right operand's sequences are
 * checked.  TRUE returned only if any pair satisfying the condition is found.
 * In strict mode, even if the desired pair has already been found, all pairs
 * still need to be examined to check the absence of errors.  If any error
 * occurs, UNKNOWN (analogous to SQL NULL) is returned.
 */
static JsonPathBool
executePredicate(JsonPathExecContext *cxt, JsonPathItem *pred,
                 JsonPathItem *larg, JsonPathItem *rarg, JsonbValue *jb,
                 bool unwrapRightArg, JsonPathPredicateCallback exec,
                 void *param)
{
    JsonPathExecResult res;
    JsonValueListIterator lseqit;
    JsonValueList lseq = {0};
    JsonValueList rseq = {0};
    JsonbValue *lval;
    bool        error = false;
    bool        found = false;

    /* Left argument is always auto-unwrapped. */
    res = executeItemOptUnwrapResultNoThrow(cxt, larg, jb, true, &lseq);
    if (jperIsError(res))
        return jpbUnknown;

    if (rarg)
    {
        /* Right argument is conditionally auto-unwrapped. */
        res = executeItemOptUnwrapResultNoThrow(cxt, rarg, jb,
                                                unwrapRightArg, &rseq);
        if (jperIsError(res))
            return jpbUnknown;
    }

    JsonValueListInitIterator(&lseq, &lseqit);
    while ((lval = JsonValueListNext(&lseq, &lseqit)))
    {
        JsonValueListIterator rseqit;
        JsonbValue *rval;
        bool        first = true;

        JsonValueListInitIterator(&rseq, &rseqit);
        if (rarg)
            rval = JsonValueListNext(&rseq, &rseqit);
        else
            rval = NULL;

        /* Loop over right arg sequence or do single pass otherwise */
        while (rarg ? (rval != NULL) : first)
        {
            JsonPathBool res = exec(pred, lval, rval, param);

            if (res == jpbUnknown)
            {
                if (jspStrictAbsenseOfErrors(cxt))
                    return jpbUnknown;

                error = true;
            }
            else if (res == jpbTrue)
            {
                if (!jspStrictAbsenseOfErrors(cxt))
                    return jpbTrue;

                found = true;
            }

            first = false;
            if (rarg)
                rval = JsonValueListNext(&rseq, &rseqit);
        }
    }

    if (found)                  /* possible only in strict mode */
        return jpbTrue;

    if (error)                  /* possible only in lax mode */
        return jpbUnknown;

    return jpbFalse;
}

/*
 * Execute binary arithmetic expression on singleton numeric operands.
 * Array operands are automatically unwrapped in lax mode.
 */
static JsonPathExecResult
executeBinaryArithmExpr(JsonPathExecContext *cxt, JsonPathItem *jsp,
                        JsonbValue *jb, BinaryArithmFunc func,
                        JsonValueList *found)
{
    JsonPathExecResult jper;
    JsonPathItem elem;
    JsonValueList lseq = {0};
    JsonValueList rseq = {0};
    JsonbValue *lval;
    JsonbValue *rval;
    Numeric     res;

    jspGetLeftArg(jsp, &elem);

    /*
     * XXX: By standard only operands of multiplicative expressions are
     * unwrapped.  We extend it to other binary arithmetic expressions too.
     */
    jper = executeItemOptUnwrapResult(cxt, &elem, jb, true, &lseq);
    if (jperIsError(jper))
        return jper;

    jspGetRightArg(jsp, &elem);

    jper = executeItemOptUnwrapResult(cxt, &elem, jb, true, &rseq);
    if (jperIsError(jper))
        return jper;

    if (JsonValueListLength(&lseq) != 1 ||
        !(lval = getScalar(JsonValueListHead(&lseq), jbvNumeric)))
        RETURN_ERROR(ereport(ERROR,
                             (errcode(ERRCODE_SINGLETON_JSON_ITEM_REQUIRED),
                              errmsg("left operand of jsonpath operator %s is not a single numeric value",
                                     jspOperationName(jsp->type)))));

    if (JsonValueListLength(&rseq) != 1 ||
        !(rval = getScalar(JsonValueListHead(&rseq), jbvNumeric)))
        RETURN_ERROR(ereport(ERROR,
                             (errcode(ERRCODE_SINGLETON_JSON_ITEM_REQUIRED),
                              errmsg("right operand of jsonpath operator %s is not a single numeric value",
                                     jspOperationName(jsp->type)))));

    if (jspThrowErrors(cxt))
    {
        res = func(lval->val.numeric, rval->val.numeric, NULL);
    }
    else
    {
        bool        error = false;

        res = func(lval->val.numeric, rval->val.numeric, &error);

        if (error)
            return jperError;
    }

    if (!jspGetNext(jsp, &elem) && !found)
        return jperOk;

    lval = palloc(sizeof(*lval));
    lval->type = jbvNumeric;
    lval->val.numeric = res;

    return executeNextItem(cxt, jsp, &elem, lval, found, false);
}

/*
 * Execute unary arithmetic expression for each numeric item in its operand's
 * sequence.  Array operand is automatically unwrapped in lax mode.
 */
static JsonPathExecResult
executeUnaryArithmExpr(JsonPathExecContext *cxt, JsonPathItem *jsp,
                       JsonbValue *jb, PGFunction func, JsonValueList *found)
{
    JsonPathExecResult jper;
    JsonPathExecResult jper2;
    JsonPathItem elem;
    JsonValueList seq = {0};
    JsonValueListIterator it;
    JsonbValue *val;
    bool        hasNext;

    jspGetArg(jsp, &elem);
    jper = executeItemOptUnwrapResult(cxt, &elem, jb, true, &seq);

    if (jperIsError(jper))
        return jper;

    jper = jperNotFound;

    hasNext = jspGetNext(jsp, &elem);

    JsonValueListInitIterator(&seq, &it);
    while ((val = JsonValueListNext(&seq, &it)))
    {
        if ((val = getScalar(val, jbvNumeric)))
        {
            if (!found && !hasNext)
                return jperOk;
        }
        else
        {
            if (!found && !hasNext)
                continue;       /* skip non-numerics processing */

            RETURN_ERROR(ereport(ERROR,
                                 (errcode(ERRCODE_JSON_NUMBER_NOT_FOUND),
                                  errmsg("operand of unary jsonpath operator %s is not a numeric value",
                                         jspOperationName(jsp->type)))));
        }

        if (func)
            val->val.numeric =
                DatumGetNumeric(DirectFunctionCall1(func,
                                                    NumericGetDatum(val->val.numeric)));

        jper2 = executeNextItem(cxt, jsp, &elem, val, found, false);

        if (jperIsError(jper2))
            return jper2;

        if (jper2 == jperOk)
        {
            if (!found)
                return jperOk;
            jper = jperOk;
        }
    }

    return jper;
}

/*
 * STARTS_WITH predicate callback.
 *
 * Check if the 'whole' string starts from 'initial' string.
 */
static JsonPathBool
executeStartsWith(JsonPathItem *jsp, JsonbValue *whole, JsonbValue *initial,
                  void *param)
{
    if (!(whole = getScalar(whole, jbvString)))
        return jpbUnknown;      /* error */

    if (!(initial = getScalar(initial, jbvString)))
        return jpbUnknown;      /* error */

    if (whole->val.string.len >= initial->val.string.len &&
        !memcmp(whole->val.string.val,
                initial->val.string.val,
                initial->val.string.len))
        return jpbTrue;

    return jpbFalse;
}

/*
 * LIKE_REGEX predicate callback.
 *
 * Check if the string matches regex pattern.
 */
static JsonPathBool
executeLikeRegex(JsonPathItem *jsp, JsonbValue *str, JsonbValue *rarg,
                 void *param)
{
    JsonLikeRegexContext *cxt = param;

    if (!(str = getScalar(str, jbvString)))
        return jpbUnknown;

    /* Cache regex text and converted flags. */
    if (!cxt->regex)
    {
        uint32      flags = jsp->content.like_regex.flags;

        cxt->regex =
            cstring_to_text_with_len(jsp->content.like_regex.pattern,
                                     jsp->content.like_regex.patternlen);

        /* Convert regex flags. */
        cxt->cflags = REG_ADVANCED;

        if (flags & JSP_REGEX_ICASE)
            cxt->cflags |= REG_ICASE;
        if (flags & JSP_REGEX_MLINE)
            cxt->cflags |= REG_NEWLINE;
        if (flags & JSP_REGEX_SLINE)
            cxt->cflags &= ~REG_NEWLINE;
        if (flags & JSP_REGEX_WSPACE)
            cxt->cflags |= REG_EXPANDED;

        /*
         * 'q' flag can work together only with 'i'.  When other is specified,
         * then 'q' has no effect.
         */
        if ((flags & JSP_REGEX_QUOTE) &&
            !(flags & (JSP_REGEX_MLINE | JSP_REGEX_SLINE | JSP_REGEX_WSPACE)))
        {
            cxt->cflags &= ~REG_ADVANCED;
            cxt->cflags |= REG_QUOTE;
        }
    }

    if (RE_compile_and_execute(cxt->regex, str->val.string.val,
                               str->val.string.len,
                               cxt->cflags, DEFAULT_COLLATION_OID, 0, NULL))
        return jpbTrue;

    return jpbFalse;
}

/*
 * Execute numeric item methods (.abs(), .floor(), .ceil()) using the specified
 * user function 'func'.
 */
static JsonPathExecResult
executeNumericItemMethod(JsonPathExecContext *cxt, JsonPathItem *jsp,
                         JsonbValue *jb, bool unwrap, PGFunction func,
                         JsonValueList *found)
{
    JsonPathItem next;
    Datum       datum;

    if (unwrap && JsonbType(jb) == jbvArray)
        return executeItemUnwrapTargetArray(cxt, jsp, jb, found, false);

    if (!(jb = getScalar(jb, jbvNumeric)))
        RETURN_ERROR(ereport(ERROR,
                             (errcode(ERRCODE_NON_NUMERIC_JSON_ITEM),
                              errmsg("jsonpath item method .%s() can only be applied to a numeric value",
                                     jspOperationName(jsp->type)))));

    datum = DirectFunctionCall1(func, NumericGetDatum(jb->val.numeric));

    if (!jspGetNext(jsp, &next) && !found)
        return jperOk;

    jb = palloc(sizeof(*jb));
    jb->type = jbvNumeric;
    jb->val.numeric = DatumGetNumeric(datum);

    return executeNextItem(cxt, jsp, &next, jb, found, false);
}

/*
 * Implementation of .keyvalue() method.
 *
 * .keyvalue() method returns a sequence of object's key-value pairs in the
 * following format: '{ "key": key, "value": value, "id": id }'.
 *
 * "id" field is an object identifier which is constructed from the two parts:
 * base object id and its binary offset in base object's jsonb:
 * id = 10000000000 * base_object_id + obj_offset_in_base_object
 *
 * 10000000000 (10^10) -- is a first round decimal number greater than 2^32
 * (maximal offset in jsonb).  Decimal multiplier is used here to improve the
 * readability of identifiers.
 *
 * Base object is usually a root object of the path: context item '$' or path
 * variable '$var', literals can't produce objects for now.  But if the path
 * contains generated objects (.keyvalue() itself, for example), then they
 * become base object for the subsequent .keyvalue().
 *
 * Id of '$' is 0. Id of '$var' is its ordinal (positive) number in the list
 * of variables (see getJsonPathVariable()).  Ids for generated objects
 * are assigned using global counter JsonPathExecContext.lastGeneratedObjectId.
 */
static JsonPathExecResult
executeKeyValueMethod(JsonPathExecContext *cxt, JsonPathItem *jsp,
                      JsonbValue *jb, JsonValueList *found)
{
    JsonPathExecResult res = jperNotFound;
    JsonPathItem next;
    JsonbContainer *jbc;
    JsonbValue  key;
    JsonbValue  val;
    JsonbValue  idval;
    JsonbValue  keystr;
    JsonbValue  valstr;
    JsonbValue  idstr;
    JsonbIterator *it;
    JsonbIteratorToken tok;
    int64       id;
    bool        hasNext;

    if (JsonbType(jb) != jbvObject || jb->type != jbvBinary)
        RETURN_ERROR(ereport(ERROR,
                             (errcode(ERRCODE_JSON_OBJECT_NOT_FOUND),
                              errmsg("jsonpath item method .%s() can only be applied to an object",
                                     jspOperationName(jsp->type)))));

    jbc = jb->val.binary.data;

    if (!JsonContainerSize(jbc))
        return jperNotFound;    /* no key-value pairs */

    hasNext = jspGetNext(jsp, &next);

    keystr.type = jbvString;
    keystr.val.string.val = "key";
    keystr.val.string.len = 3;

    valstr.type = jbvString;
    valstr.val.string.val = "value";
    valstr.val.string.len = 5;

    idstr.type = jbvString;
    idstr.val.string.val = "id";
    idstr.val.string.len = 2;

    /* construct object id from its base object and offset inside that */
    id = jb->type != jbvBinary ? 0 :
        (int64) ((char *) jbc - (char *) cxt->baseObject.jbc);
    id += (int64) cxt->baseObject.id * INT64CONST(10000000000);

    idval.type = jbvNumeric;
    idval.val.numeric = DatumGetNumeric(DirectFunctionCall1(int8_numeric,
                                                            Int64GetDatum(id)));

    it = JsonbIteratorInit(jbc);

    while ((tok = JsonbIteratorNext(&it, &key, true)) != WJB_DONE)
    {
        JsonBaseObjectInfo baseObject;
        JsonbValue  obj;
        JsonbParseState *ps;
        JsonbValue *keyval;
        Jsonb      *jsonb;

        if (tok != WJB_KEY)
            continue;

        res = jperOk;

        if (!hasNext && !found)
            break;

        tok = JsonbIteratorNext(&it, &val, true);
        Assert(tok == WJB_VALUE);

        ps = NULL;
        pushJsonbValue(&ps, WJB_BEGIN_OBJECT, NULL);

        pushJsonbValue(&ps, WJB_KEY, &keystr);
        pushJsonbValue(&ps, WJB_VALUE, &key);

        pushJsonbValue(&ps, WJB_KEY, &valstr);
        pushJsonbValue(&ps, WJB_VALUE, &val);

        pushJsonbValue(&ps, WJB_KEY, &idstr);
        pushJsonbValue(&ps, WJB_VALUE, &idval);

        keyval = pushJsonbValue(&ps, WJB_END_OBJECT, NULL);

        jsonb = JsonbValueToJsonb(keyval);

        JsonbInitBinary(&obj, jsonb);

        baseObject = setBaseObject(cxt, &obj, cxt->lastGeneratedObjectId++);

        res = executeNextItem(cxt, jsp, &next, &obj, found, true);

        cxt->baseObject = baseObject;

        if (jperIsError(res))
            return res;

        if (res == jperOk && !found)
            break;
    }

    return res;
}

/*
 * Convert boolean execution status 'res' to a boolean JSON item and execute
 * next jsonpath.
 */
static JsonPathExecResult
appendBoolResult(JsonPathExecContext *cxt, JsonPathItem *jsp,
                 JsonValueList *found, JsonPathBool res)
{
    JsonPathItem next;
    JsonbValue  jbv;

    if (!jspGetNext(jsp, &next) && !found)
        return jperOk;          /* found singleton boolean value */

    if (res == jpbUnknown)
    {
        jbv.type = jbvNull;
    }
    else
    {
        jbv.type = jbvBool;
        jbv.val.boolean = res == jpbTrue;
    }

    return executeNextItem(cxt, jsp, &next, &jbv, found, true);
}

/*
 * Convert jsonpath's scalar or variable node to actual jsonb value.
 *
 * If node is a variable then its id returned, otherwise 0 returned.
 */
static void
getJsonPathItem(JsonPathExecContext *cxt, JsonPathItem *item,
                JsonbValue *value)
{
    switch (item->type)
    {
        case jpiNull:
            value->type = jbvNull;
            break;
        case jpiBool:
            value->type = jbvBool;
            value->val.boolean = jspGetBool(item);
            break;
        case jpiNumeric:
            value->type = jbvNumeric;
            value->val.numeric = jspGetNumeric(item);
            break;
        case jpiString:
            value->type = jbvString;
            value->val.string.val = jspGetString(item,
                                                 &value->val.string.len);
            break;
        case jpiVariable:
            getJsonPathVariable(cxt, item, cxt->vars, value);
            return;
        default:
            elog(ERROR, "unexpected jsonpath item type");
    }
}

/*
 * Get the value of variable passed to jsonpath executor
 */
static void
getJsonPathVariable(JsonPathExecContext *cxt, JsonPathItem *variable,
                    Jsonb *vars, JsonbValue *value)
{
    char       *varName;
    int         varNameLength;
    JsonbValue  tmp;
    JsonbValue *v;

    if (!vars)
    {
        value->type = jbvNull;
        return;
    }

    Assert(variable->type == jpiVariable);
    varName = jspGetString(variable, &varNameLength);
    tmp.type = jbvString;
    tmp.val.string.val = varName;
    tmp.val.string.len = varNameLength;

    v = findJsonbValueFromContainer(&vars->root, JB_FOBJECT, &tmp);

    if (v)
    {
        *value = *v;
        pfree(v);
    }
    else
    {
        ereport(ERROR,
                (errcode(ERRCODE_UNDEFINED_OBJECT),
                 errmsg("could not find jsonpath variable \"%s\"",
                        pnstrdup(varName, varNameLength))));
    }

    JsonbInitBinary(&tmp, vars);
    setBaseObject(cxt, &tmp, 1);
}

/**************** Support functions for JsonPath execution *****************/

/*
 * Returns the size of an array item, or -1 if item is not an array.
 */
static int
JsonbArraySize(JsonbValue *jb)
{
    Assert(jb->type != jbvArray);

    if (jb->type == jbvBinary)
    {
        JsonbContainer *jbc = jb->val.binary.data;

        if (JsonContainerIsArray(jbc) && !JsonContainerIsScalar(jbc))
            return JsonContainerSize(jbc);
    }

    return -1;
}

/* Comparison predicate callback. */
static JsonPathBool
executeComparison(JsonPathItem *cmp, JsonbValue *lv, JsonbValue *rv, void *p)
{
    return compareItems(cmp->type, lv, rv);
}

/*
 * Perform per-byte comparison of two strings.
 */
static int
binaryCompareStrings(const char *s1, int len1,
                     const char *s2, int len2)
{
    int         cmp;

    cmp = memcmp(s1, s2, Min(len1, len2));

    if (cmp != 0)
        return cmp;

    if (len1 == len2)
        return 0;

    return len1 < len2 ? -1 : 1;
}

/*
 * Compare two strings in the current server encoding using Unicode codepoint
 * collation.
 */
static int
compareStrings(const char *mbstr1, int mblen1,
               const char *mbstr2, int mblen2)
{
    if (GetDatabaseEncoding() == PG_SQL_ASCII ||
        GetDatabaseEncoding() == PG_UTF8)
    {
        /*
         * It's known property of UTF-8 strings that their per-byte comparison
         * result matches codepoints comparison result.  ASCII can be
         * considered as special case of UTF-8.
         */
        return binaryCompareStrings(mbstr1, mblen1, mbstr2, mblen2);
    }
    else
    {
        char       *utf8str1,
                   *utf8str2;
        int         cmp,
                    utf8len1,
                    utf8len2;

        /*
         * We have to convert other encodings to UTF-8 first, then compare.
         * Input strings may be not null-terminated and pg_server_to_any() may
         * return them "as is".  So, use strlen() only if there is real
         * conversion.
         */
        utf8str1 = pg_server_to_any(mbstr1, mblen1, PG_UTF8);
        utf8str2 = pg_server_to_any(mbstr2, mblen2, PG_UTF8);
        utf8len1 = (mbstr1 == utf8str1) ? mblen1 : strlen(utf8str1);
        utf8len2 = (mbstr2 == utf8str2) ? mblen2 : strlen(utf8str2);

        cmp = binaryCompareStrings(utf8str1, utf8len1, utf8str2, utf8len2);

        /*
         * If pg_server_to_any() did no real conversion, then we actually
         * compared original strings.  So, we already done.
         */
        if (mbstr1 == utf8str1 && mbstr2 == utf8str2)
            return cmp;

        /* Free memory if needed */
        if (mbstr1 != utf8str1)
            pfree(utf8str1);
        if (mbstr2 != utf8str2)
            pfree(utf8str2);

        /*
         * When all Unicode codepoints are equal, return result of binary
         * comparison.  In some edge cases, same characters may have different
         * representations in encoding.  Then our behavior could diverge from
         * standard.  However, that allow us to do simple binary comparison
         * for "==" operator, which is performance critical in typical cases.
         * In future to implement strict standard conformance, we can do
         * normalization of input JSON strings.
         */
        if (cmp == 0)
            return binaryCompareStrings(mbstr1, mblen1, mbstr2, mblen2);
        else
            return cmp;
    }
}

/*
 * Compare two SQL/JSON items using comparison operation 'op'.
 */
static JsonPathBool
compareItems(int32 op, JsonbValue *jb1, JsonbValue *jb2)
{
    int         cmp;
    bool        res;

    if (jb1->type != jb2->type)
    {
        if (jb1->type == jbvNull || jb2->type == jbvNull)

            /*
             * Equality and order comparison of nulls to non-nulls returns
             * always false, but inequality comparison returns true.
             */
            return op == jpiNotEqual ? jpbTrue : jpbFalse;

        /* Non-null items of different types are not comparable. */
        return jpbUnknown;
    }

    switch (jb1->type)
    {
        case jbvNull:
            cmp = 0;
            break;
        case jbvBool:
            cmp = jb1->val.boolean == jb2->val.boolean ? 0 :
                jb1->val.boolean ? 1 : -1;
            break;
        case jbvNumeric:
            cmp = compareNumeric(jb1->val.numeric, jb2->val.numeric);
            break;
        case jbvString:
            if (op == jpiEqual)
                return jb1->val.string.len != jb2->val.string.len ||
                    memcmp(jb1->val.string.val,
                           jb2->val.string.val,
                           jb1->val.string.len) ? jpbFalse : jpbTrue;

            cmp = compareStrings(jb1->val.string.val, jb1->val.string.len,
                                 jb2->val.string.val, jb2->val.string.len);
            break;

        case jbvBinary:
        case jbvArray:
        case jbvObject:
            return jpbUnknown;  /* non-scalars are not comparable */

        default:
            elog(ERROR, "invalid jsonb value type %d", jb1->type);
    }

    switch (op)
    {
        case jpiEqual:
            res = (cmp == 0);
            break;
        case jpiNotEqual:
            res = (cmp != 0);
            break;
        case jpiLess:
            res = (cmp < 0);
            break;
        case jpiGreater:
            res = (cmp > 0);
            break;
        case jpiLessOrEqual:
            res = (cmp <= 0);
            break;
        case jpiGreaterOrEqual:
            res = (cmp >= 0);
            break;
        default:
            elog(ERROR, "unrecognized jsonpath operation: %d", op);
            return jpbUnknown;
    }

    return res ? jpbTrue : jpbFalse;
}

/* Compare two numerics */
static int
compareNumeric(Numeric a, Numeric b)
{
    return DatumGetInt32(DirectFunctionCall2(numeric_cmp,
                                             NumericGetDatum(a),
                                             NumericGetDatum(b)));
}

static JsonbValue *
copyJsonbValue(JsonbValue *src)
{
    JsonbValue *dst = palloc(sizeof(*dst));

    *dst = *src;

    return dst;
}

/*
 * Execute array subscript expression and convert resulting numeric item to
 * the integer type with truncation.
 */
static JsonPathExecResult
getArrayIndex(JsonPathExecContext *cxt, JsonPathItem *jsp, JsonbValue *jb,
              int32 *index)
{
    JsonbValue *jbv;
    JsonValueList found = {0};
    JsonPathExecResult res = executeItem(cxt, jsp, jb, &found);
    Datum       numeric_index;
    bool        have_error = false;

    if (jperIsError(res))
        return res;

    if (JsonValueListLength(&found) != 1 ||
        !(jbv = getScalar(JsonValueListHead(&found), jbvNumeric)))
        RETURN_ERROR(ereport(ERROR,
                             (errcode(ERRCODE_INVALID_JSON_SUBSCRIPT),
                              errmsg("jsonpath array subscript is not a single numeric value"))));

    numeric_index = DirectFunctionCall2(numeric_trunc,
                                        NumericGetDatum(jbv->val.numeric),
                                        Int32GetDatum(0));

    *index = numeric_int4_opt_error(DatumGetNumeric(numeric_index),
                                    &have_error);

    if (have_error)
        RETURN_ERROR(ereport(ERROR,
                             (errcode(ERRCODE_INVALID_JSON_SUBSCRIPT),
                              errmsg("jsonpath array subscript is out of integer range"))));

    return jperOk;
}

/* Save base object and its id needed for the execution of .keyvalue(). */
static JsonBaseObjectInfo
setBaseObject(JsonPathExecContext *cxt, JsonbValue *jbv, int32 id)
{
    JsonBaseObjectInfo baseObject = cxt->baseObject;

    cxt->baseObject.jbc = jbv->type != jbvBinary ? NULL :
        (JsonbContainer *) jbv->val.binary.data;
    cxt->baseObject.id = id;

    return baseObject;
}

static void
JsonValueListAppend(JsonValueList *jvl, JsonbValue *jbv)
{
    if (jvl->singleton)
    {
        jvl->list = list_make2(jvl->singleton, jbv);
        jvl->singleton = NULL;
    }
    else if (!jvl->list)
        jvl->singleton = jbv;
    else
        jvl->list = lappend(jvl->list, jbv);
}

static int
JsonValueListLength(const JsonValueList *jvl)
{
    return jvl->singleton ? 1 : list_length(jvl->list);
}

static bool
JsonValueListIsEmpty(JsonValueList *jvl)
{
    return !jvl->singleton && list_length(jvl->list) <= 0;
}

static JsonbValue *
JsonValueListHead(JsonValueList *jvl)
{
    return jvl->singleton ? jvl->singleton : linitial(jvl->list);
}

static List *
JsonValueListGetList(JsonValueList *jvl)
{
    if (jvl->singleton)
        return list_make1(jvl->singleton);

    return jvl->list;
}

static void
JsonValueListInitIterator(const JsonValueList *jvl, JsonValueListIterator *it)
{
    if (jvl->singleton)
    {
        it->value = jvl->singleton;
        it->list = NIL;
        it->next = NULL;
    }
    else if (jvl->list != NIL)
    {
        it->value = (JsonbValue *) linitial(jvl->list);
        it->list = jvl->list;
        it->next = list_second_cell(jvl->list);
    }
    else
    {
        it->value = NULL;
        it->list = NIL;
        it->next = NULL;
    }
}

/*
 * Get the next item from the sequence advancing iterator.
 */
static JsonbValue *
JsonValueListNext(const JsonValueList *jvl, JsonValueListIterator *it)
{
    JsonbValue *result = it->value;

    if (it->next)
    {
        it->value = lfirst(it->next);
        it->next = lnext(it->list, it->next);
    }
    else
    {
        it->value = NULL;
    }

    return result;
}

/*
 * Initialize a binary JsonbValue with the given jsonb container.
 */
static JsonbValue *
JsonbInitBinary(JsonbValue *jbv, Jsonb *jb)
{
    jbv->type = jbvBinary;
    jbv->val.binary.data = &jb->root;
    jbv->val.binary.len = VARSIZE_ANY_EXHDR(jb);

    return jbv;
}

/*
 * Returns jbv* type of of JsonbValue. Note, it never returns jbvBinary as is.
 */
static int
JsonbType(JsonbValue *jb)
{
    int         type = jb->type;

    if (jb->type == jbvBinary)
    {
        JsonbContainer *jbc = (void *) jb->val.binary.data;

        /* Scalars should be always extracted during jsonpath execution. */
        Assert(!JsonContainerIsScalar(jbc));

        if (JsonContainerIsObject(jbc))
            type = jbvObject;
        else if (JsonContainerIsArray(jbc))
            type = jbvArray;
        else
            elog(ERROR, "invalid jsonb container type: 0x%08x", jbc->header);
    }

    return type;
}

/* Get scalar of given type or NULL on type mismatch */
static JsonbValue *
getScalar(JsonbValue *scalar, enum jbvType type)
{
    /* Scalars should be always extracted during jsonpath execution. */
    Assert(scalar->type != jbvBinary ||
           !JsonContainerIsScalar(scalar->val.binary.data));

    return scalar->type == type ? scalar : NULL;
}

/* Construct a JSON array from the item list */
static JsonbValue *
wrapItemsInArray(const JsonValueList *items)
{
    JsonbParseState *ps = NULL;
    JsonValueListIterator it;
    JsonbValue *jbv;

    pushJsonbValue(&ps, WJB_BEGIN_ARRAY, NULL);

    JsonValueListInitIterator(items, &it);
    while ((jbv = JsonValueListNext(items, &it)))
        pushJsonbValue(&ps, WJB_ELEM, jbv);

    return pushJsonbValue(&ps, WJB_END_ARRAY, NULL);
}