extended_stats_funcs.c

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/*-------------------------------------------------------------------------
 *
 * extended_stats_funcs.c
 *    Functions for manipulating extended statistics.
 *
 * This file includes the set of facilities required to support the direct
 * manipulations of extended statistics objects.
 *
 * Portions Copyright (c) 1996-2026, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * IDENTIFICATION
 *    src/backend/statistics/extended_stats_funcs.c
 *
 *-------------------------------------------------------------------------
 */
#include "postgres.h"
 
#include "access/heapam.h"
#include "catalog/indexing.h"
#include "catalog/namespace.h"
#include "catalog/pg_collation_d.h"
#include "catalog/pg_database.h"
#include "catalog/pg_operator.h"
#include "catalog/pg_statistic_ext.h"
#include "catalog/pg_statistic_ext_data.h"
#include "miscadmin.h"
#include "nodes/makefuncs.h"
#include "nodes/nodeFuncs.h"
#include "optimizer/optimizer.h"
#include "statistics/extended_stats_internal.h"
#include "statistics/stat_utils.h"
#include "utils/acl.h"
#include "utils/array.h"
#include "utils/builtins.h"
#include "utils/fmgroids.h"
#include "utils/jsonb.h"
#include "utils/lsyscache.h"
#include "utils/syscache.h"
#include "utils/typcache.h"
 
 
/*
 * Index of the arguments for the SQL functions.
 */
enum extended_stats_argnum
{
    RELSCHEMA_ARG = 0,
    RELNAME_ARG,
    STATSCHEMA_ARG,
    STATNAME_ARG,
    INHERITED_ARG,
    NDISTINCT_ARG,
    DEPENDENCIES_ARG,
    MOST_COMMON_VALS_ARG,
    MOST_COMMON_FREQS_ARG,
    MOST_COMMON_BASE_FREQS_ARG,
    EXPRESSIONS_ARG,
    NUM_EXTENDED_STATS_ARGS,
};
 
/*
 * The argument names and type OIDs of the arguments for the SQL
 * functions.
 */
static struct StatsArgInfo extarginfo[] =
{
    [RELSCHEMA_ARG] = {"schemaname", TEXTOID},
    [RELNAME_ARG] = {"relname", TEXTOID},
    [STATSCHEMA_ARG] = {"statistics_schemaname", TEXTOID},
    [STATNAME_ARG] = {"statistics_name", TEXTOID},
    [INHERITED_ARG] = {"inherited", BOOLOID},
    [NDISTINCT_ARG] = {"n_distinct", PG_NDISTINCTOID},
    [DEPENDENCIES_ARG] = {"dependencies", PG_DEPENDENCIESOID},
    [MOST_COMMON_VALS_ARG] = {"most_common_vals", TEXTARRAYOID},
    [MOST_COMMON_FREQS_ARG] = {"most_common_freqs", FLOAT8ARRAYOID},
    [MOST_COMMON_BASE_FREQS_ARG] = {"most_common_base_freqs", FLOAT8ARRAYOID},
    [EXPRESSIONS_ARG] = {"exprs", JSONBOID},
    [NUM_EXTENDED_STATS_ARGS] = {0},
};
 
/*
 * An index of the elements of a stxdexpr Datum, which repeat for each
 * expression in the extended statistics object.
 */
enum extended_stats_exprs_element
{
    NULL_FRAC_ELEM = 0,
    AVG_WIDTH_ELEM,
    N_DISTINCT_ELEM,
    MOST_COMMON_VALS_ELEM,
    MOST_COMMON_FREQS_ELEM,
    HISTOGRAM_BOUNDS_ELEM,
    CORRELATION_ELEM,
    MOST_COMMON_ELEMS_ELEM,
    MOST_COMMON_ELEM_FREQS_ELEM,
    ELEM_COUNT_HISTOGRAM_ELEM,
    RANGE_LENGTH_HISTOGRAM_ELEM,
    RANGE_EMPTY_FRAC_ELEM,
    RANGE_BOUNDS_HISTOGRAM_ELEM,
    NUM_ATTRIBUTE_STATS_ELEMS
};
 
/*
 * The argument names of the repeating arguments for stxdexpr.
 */
static const char *extexprargname[NUM_ATTRIBUTE_STATS_ELEMS] =
{
    "null_frac",
    "avg_width",
    "n_distinct",
    "most_common_vals",
    "most_common_freqs",
    "histogram_bounds",
    "correlation",
    "most_common_elems",
    "most_common_elem_freqs",
    "elem_count_histogram",
    "range_length_histogram",
    "range_empty_frac",
    "range_bounds_histogram"
};
 
static bool extended_statistics_update(FunctionCallInfo fcinfo);
 
static HeapTuple get_pg_statistic_ext(Relation pg_stext, Oid nspoid,
                                      const char *stxname);
static bool delete_pg_statistic_ext_data(Oid stxoid, bool inherited);
 
/*
 * Track the extended statistics kinds expected for a pg_statistic_ext
 * tuple.
 */
typedef struct
{
    bool        ndistinct;
    bool        dependencies;
    bool        mcv;
    bool        expressions;
} StakindFlags;
 
static void expand_stxkind(HeapTuple tup, StakindFlags *enabled);
static void upsert_pg_statistic_ext_data(const Datum *values,
                                         const bool *nulls,
                                         const bool *replaces);
 
static bool check_mcvlist_array(const ArrayType *arr, int argindex,
                                int required_ndims, int mcv_length);
static Datum import_expressions(Relation pgsd, int numexprs,
                                Oid *atttypids, int32 *atttypmods,
                                Oid *atttypcolls, Jsonb *exprs_jsonb,
                                bool *exprs_is_perfect);
static Datum import_mcv(const ArrayType *mcv_arr,
                        const ArrayType *freqs_arr,
                        const ArrayType *base_freqs_arr,
                        Oid *atttypids, int32 *atttypmods,
                        Oid *atttypcolls, int numattrs,
                        bool *ok);
 
static char *jbv_string_get_cstr(JsonbValue *jval);
static bool jbv_to_infunc_datum(JsonbValue *jval, PGFunction func,
                                AttrNumber exprnum, const char *argname,
                                Datum *datum);
static bool key_in_expr_argnames(JsonbValue *key);
static bool check_all_expr_argnames_valid(JsonbContainer *cont, AttrNumber exprnum);
static Datum array_in_safe(FmgrInfo *array_in, const char *s, Oid typid,
                           int32 typmod, AttrNumber exprnum,
                           const char *element_name, bool *ok);
static Datum import_pg_statistic(Relation pgsd, JsonbContainer *cont,
                                 AttrNumber exprnum, FmgrInfo *array_in_fn,
                                 Oid typid, int32 typmod, Oid typcoll,
                                 bool *pg_statistic_ok);
 
/*
 * Fetch a pg_statistic_ext row by name and namespace OID.
 */
static HeapTuple
get_pg_statistic_ext(Relation pg_stext, Oid nspoid, const char *stxname)
{
    ScanKeyData key[2];
    SysScanDesc scan;
    HeapTuple   tup;
    Oid         stxoid = InvalidOid;
 
    ScanKeyInit(&key[0],
                Anum_pg_statistic_ext_stxname,
                BTEqualStrategyNumber,
                F_NAMEEQ,
                CStringGetDatum(stxname));
    ScanKeyInit(&key[1],
                Anum_pg_statistic_ext_stxnamespace,
                BTEqualStrategyNumber,
                F_OIDEQ,
                ObjectIdGetDatum(nspoid));
 
    /*
     * Try to find matching pg_statistic_ext row.
     */
    scan = systable_beginscan(pg_stext,
                              StatisticExtNameIndexId,
                              true,
                              NULL,
                              2,
                              key);
 
    /* Lookup is based on a unique index, so we get either 0 or 1 tuple. */
    tup = systable_getnext(scan);
 
    if (HeapTupleIsValid(tup))
        stxoid = ((Form_pg_statistic_ext) GETSTRUCT(tup))->oid;
 
    systable_endscan(scan);
 
    if (!OidIsValid(stxoid))
        return NULL;
 
    return SearchSysCacheCopy1(STATEXTOID, ObjectIdGetDatum(stxoid));
}
 
/*
 * Decode the stxkind column so that we know which stats types to expect,
 * returning a StakindFlags set depending on the stats kinds expected by
 * a pg_statistic_ext tuple.
 */
static void
expand_stxkind(HeapTuple tup, StakindFlags *enabled)
{
    Datum       datum;
    ArrayType  *arr;
    char       *kinds;
 
    datum = SysCacheGetAttrNotNull(STATEXTOID,
                                   tup,
                                   Anum_pg_statistic_ext_stxkind);
    arr = DatumGetArrayTypeP(datum);
    if (ARR_NDIM(arr) != 1 || ARR_HASNULL(arr) || ARR_ELEMTYPE(arr) != CHAROID)
        elog(ERROR, "stxkind is not a one-dimension char array");
 
    kinds = (char *) ARR_DATA_PTR(arr);
 
    for (int i = 0; i < ARR_DIMS(arr)[0]; i++)
    {
        switch (kinds[i])
        {
            case STATS_EXT_NDISTINCT:
                enabled->ndistinct = true;
                break;
            case STATS_EXT_DEPENDENCIES:
                enabled->dependencies = true;
                break;
            case STATS_EXT_MCV:
                enabled->mcv = true;
                break;
            case STATS_EXT_EXPRESSIONS:
                enabled->expressions = true;
                break;
            default:
                elog(ERROR, "incorrect stxkind %c found", kinds[i]);
                break;
        }
    }
}
 
/*
 * Perform the actual storage of a pg_statistic_ext_data tuple.
 */
static void
upsert_pg_statistic_ext_data(const Datum *values, const bool *nulls,
                             const bool *replaces)
{
    Relation    pg_stextdata;
    HeapTuple   stxdtup;
    HeapTuple   newtup;
 
    pg_stextdata = table_open(StatisticExtDataRelationId, RowExclusiveLock);
 
    stxdtup = SearchSysCache2(STATEXTDATASTXOID,
                              values[Anum_pg_statistic_ext_data_stxoid - 1],
                              values[Anum_pg_statistic_ext_data_stxdinherit - 1]);
 
    if (HeapTupleIsValid(stxdtup))
    {
        newtup = heap_modify_tuple(stxdtup,
                                   RelationGetDescr(pg_stextdata),
                                   values,
                                   nulls,
                                   replaces);
        CatalogTupleUpdate(pg_stextdata, &newtup->t_self, newtup);
        ReleaseSysCache(stxdtup);
    }
    else
    {
        newtup = heap_form_tuple(RelationGetDescr(pg_stextdata), values, nulls);
        CatalogTupleInsert(pg_stextdata, newtup);
    }
 
    heap_freetuple(newtup);
 
    CommandCounterIncrement();
 
    table_close(pg_stextdata, RowExclusiveLock);
}
 
/*
 * Insert or update an extended statistics object.
 *
 * Major errors, such as the table not existing or permission errors, are
 * reported as ERRORs.  There are a couple of paths that generate a WARNING,
 * like when the statistics object or its schema do not exist, a conversion
 * failure on one statistic kind, or when other statistic kinds may still
 * be updated.
 */
static bool
extended_statistics_update(FunctionCallInfo fcinfo)
{
    char       *relnspname;
    char       *relname;
    Oid         nspoid;
    char       *nspname;
    char       *stxname;
    bool        inherited;
    Relation    pg_stext = NULL;
    HeapTuple   tup = NULL;
 
    StakindFlags enabled = {false, false, false, false};
    StakindFlags has = {false, false, false, false};
 
    Form_pg_statistic_ext stxform;
 
    Datum       values[Natts_pg_statistic_ext_data] = {0};
    bool        nulls[Natts_pg_statistic_ext_data] = {0};
    bool        replaces[Natts_pg_statistic_ext_data] = {0};
    bool        success = true;
    Datum       exprdatum;
    bool        isnull;
    List       *exprs = NIL;
    int         numattnums = 0;
    int         numexprs = 0;
    int         numattrs = 0;
 
    /* arrays of type info, if we need them */
    Oid        *atttypids = NULL;
    int32      *atttypmods = NULL;
    Oid        *atttypcolls = NULL;
    Oid         relid;
    Oid         locked_table = InvalidOid;
 
    /*
     * Fill out the StakindFlags "has" structure based on which parameters
     * were provided to the function.
     *
     * The MCV stats composite value is an array of record type, but this is
     * externally represented as three arrays that must be interleaved into
     * the array of records (pg_stats_ext stores four arrays,
     * most_common_val_nulls is built from the contents of most_common_vals).
     * Therefore, none of the three array values is meaningful unless the
     * other two are also present and in sync in terms of array length.
     */
    has.mcv = (!PG_ARGISNULL(MOST_COMMON_VALS_ARG) &&
               !PG_ARGISNULL(MOST_COMMON_FREQS_ARG) &&
               !PG_ARGISNULL(MOST_COMMON_BASE_FREQS_ARG));
    has.ndistinct = !PG_ARGISNULL(NDISTINCT_ARG);
    has.dependencies = !PG_ARGISNULL(DEPENDENCIES_ARG);
    has.expressions = !PG_ARGISNULL(EXPRESSIONS_ARG);
 
    if (RecoveryInProgress())
    {
        ereport(WARNING,
                errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
                errmsg("recovery is in progress"),
                errhint("Statistics cannot be modified during recovery."));
        return false;
    }
 
    /* relation arguments */
    stats_check_required_arg(fcinfo, extarginfo, RELSCHEMA_ARG);
    relnspname = TextDatumGetCString(PG_GETARG_DATUM(RELSCHEMA_ARG));
    stats_check_required_arg(fcinfo, extarginfo, RELNAME_ARG);
    relname = TextDatumGetCString(PG_GETARG_DATUM(RELNAME_ARG));
 
    /* extended statistics arguments */
    stats_check_required_arg(fcinfo, extarginfo, STATSCHEMA_ARG);
    nspname = TextDatumGetCString(PG_GETARG_DATUM(STATSCHEMA_ARG));
    stats_check_required_arg(fcinfo, extarginfo, STATNAME_ARG);
    stxname = TextDatumGetCString(PG_GETARG_DATUM(STATNAME_ARG));
    stats_check_required_arg(fcinfo, extarginfo, INHERITED_ARG);
    inherited = PG_GETARG_BOOL(INHERITED_ARG);
 
    /*
     * First open the relation where we expect to find the statistics.  This
     * is similar to relation and attribute statistics, so as ACL checks are
     * done before any locks are taken, even before any attempts related to
     * the extended stats object.
     */
    relid = RangeVarGetRelidExtended(makeRangeVar(relnspname, relname, -1),
                                     ShareUpdateExclusiveLock, 0,
                                     RangeVarCallbackForStats, &locked_table);
 
    nspoid = get_namespace_oid(nspname, true);
    if (nspoid == InvalidOid)
    {
        ereport(WARNING,
                errcode(ERRCODE_UNDEFINED_OBJECT),
                errmsg("could not find schema \"%s\"", nspname));
        success = false;
        goto cleanup;
    }
 
    pg_stext = table_open(StatisticExtRelationId, RowExclusiveLock);
    tup = get_pg_statistic_ext(pg_stext, nspoid, stxname);
 
    if (!HeapTupleIsValid(tup))
    {
        ereport(WARNING,
                errcode(ERRCODE_UNDEFINED_OBJECT),
                errmsg("could not find extended statistics object \"%s.%s\"",
                       nspname, stxname));
        success = false;
        goto cleanup;
    }
 
    stxform = (Form_pg_statistic_ext) GETSTRUCT(tup);
 
    /*
     * The relation tracked by the stats object has to match with the relation
     * we have already locked.
     */
    if (stxform->stxrelid != relid)
    {
        ereport(WARNING,
                errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                errmsg("could not restore extended statistics object \"%s.%s\": incorrect relation \"%s.%s\" specified",
                       nspname, stxname,
                       relnspname, relname));
 
        success = false;
        goto cleanup;
    }
 
    /* Find out what extended statistics kinds we should expect. */
    expand_stxkind(tup, &enabled);
    numattnums = stxform->stxkeys.dim1;
 
    /* decode expression (if any) */
    exprdatum = SysCacheGetAttr(STATEXTOID,
                                tup,
                                Anum_pg_statistic_ext_stxexprs,
                                &isnull);
    if (!isnull)
    {
        char       *s;
 
        s = TextDatumGetCString(exprdatum);
        exprs = (List *) stringToNode(s);
        pfree(s);
 
        /*
         * Run the expressions through eval_const_expressions().  This is not
         * just an optimization, but is necessary, because the planner will be
         * comparing them to similarly-processed qual clauses, and may fail to
         * detect valid matches without this.
         *
         * We must not use canonicalize_qual(), however, since these are not
         * qual expressions.
         */
        exprs = (List *) eval_const_expressions(NULL, (Node *) exprs);
 
        /* May as well fix opfuncids too */
        fix_opfuncids((Node *) exprs);
 
        /* Compute the number of expression, for input validation. */
        numexprs = list_length(exprs);
    }
 
    numattrs = numattnums + numexprs;
 
    /*
     * If the object cannot support ndistinct, we should not have data for it.
     */
    if (has.ndistinct && !enabled.ndistinct)
    {
        ereport(WARNING,
                errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                errmsg("cannot specify parameter \"%s\"",
                       extarginfo[NDISTINCT_ARG].argname),
                errhint("Extended statistics object \"%s.%s\" does not support statistics of this type.",
                        nspname, stxname));
 
        has.ndistinct = false;
        success = false;
    }
 
    /*
     * If the object cannot support dependencies, we should not have data for
     * it.
     */
    if (has.dependencies && !enabled.dependencies)
    {
        ereport(WARNING,
                errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                errmsg("cannot specify parameter \"%s\"",
                       extarginfo[DEPENDENCIES_ARG].argname),
                errhint("Extended statistics object \"%s.%s\" does not support statistics of this type.",
                        nspname, stxname));
        has.dependencies = false;
        success = false;
    }
 
    /*
     * If the object cannot hold an MCV value, but any of the MCV parameters
     * are set, then issue a WARNING and ensure that we do not try to load MCV
     * stats later.  In pg_stats_ext, most_common_val_nulls, most_common_freqs
     * and most_common_base_freqs are NULL if most_common_vals is NULL.
     */
    if (!enabled.mcv)
    {
        if (!PG_ARGISNULL(MOST_COMMON_VALS_ARG) ||
            !PG_ARGISNULL(MOST_COMMON_FREQS_ARG) ||
            !PG_ARGISNULL(MOST_COMMON_BASE_FREQS_ARG))
        {
            ereport(WARNING,
                    errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                    errmsg("cannot specify parameters \"%s\", \"%s\" or \"%s\"",
                           extarginfo[MOST_COMMON_VALS_ARG].argname,
                           extarginfo[MOST_COMMON_FREQS_ARG].argname,
                           extarginfo[MOST_COMMON_BASE_FREQS_ARG].argname),
                    errhint("Extended statistics object \"%s.%s\" does not support statistics of this type.",
                            nspname, stxname));
 
            has.mcv = false;
            success = false;
        }
    }
    else if (!has.mcv)
    {
        /*
         * If we do not have all of the MCV arrays set while the extended
         * statistics object expects something, something is wrong.  This
         * issues a WARNING if a partial input has been provided.
         */
        if (!PG_ARGISNULL(MOST_COMMON_VALS_ARG) ||
            !PG_ARGISNULL(MOST_COMMON_FREQS_ARG) ||
            !PG_ARGISNULL(MOST_COMMON_BASE_FREQS_ARG))
        {
            ereport(WARNING,
                    errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                    errmsg("could not use \"%s\", \"%s\" and \"%s\": missing one or more parameters",
                           extarginfo[MOST_COMMON_VALS_ARG].argname,
                           extarginfo[MOST_COMMON_FREQS_ARG].argname,
                           extarginfo[MOST_COMMON_BASE_FREQS_ARG].argname));
            success = false;
        }
    }
 
    /*
     * If the object cannot support expressions, we should not have data for
     * them.
     */
    if (has.expressions && !enabled.expressions)
    {
        ereport(WARNING,
                errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                errmsg("cannot specify parameter \"%s\"",
                       extarginfo[EXPRESSIONS_ARG].argname),
                errhint("Extended statistics object \"%s.%s\" does not support statistics of this type.",
                        nspname, stxname));
 
        has.expressions = false;
        success = false;
    }
 
    /*
     * Either of these statistic types requires that we supply a semi-filled
     * VacAttrStatsP array.
     *
     * It is not possible to use the existing lookup_var_attr_stats() and
     * examine_attribute() because these functions will skip attributes where
     * attstattarget is 0, and we may have statistics data to import for those
     * attributes.
     */
    if (has.mcv || has.expressions)
    {
        atttypids = palloc0_array(Oid, numattrs);
        atttypmods = palloc0_array(int32, numattrs);
        atttypcolls = palloc0_array(Oid, numattrs);
 
        /*
         * The leading stxkeys are attribute numbers up through numattnums.
         * These keys must be in ascending AttrNumber order, but we do not
         * rely on that.
         */
        for (int i = 0; i < numattnums; i++)
        {
            AttrNumber  attnum = stxform->stxkeys.values[i];
            HeapTuple   atup = SearchSysCache2(ATTNUM,
                                               ObjectIdGetDatum(relid),
                                               Int16GetDatum(attnum));
 
            Form_pg_attribute attr;
 
            /* Attribute not found */
            if (!HeapTupleIsValid(atup))
                elog(ERROR, "stxkeys references nonexistent attnum %d", attnum);
 
            attr = (Form_pg_attribute) GETSTRUCT(atup);
 
            if (attr->attisdropped)
                elog(ERROR, "stxkeys references dropped attnum %d", attnum);
 
            atttypids[i] = attr->atttypid;
            atttypmods[i] = attr->atttypmod;
            atttypcolls[i] = attr->attcollation;
            ReleaseSysCache(atup);
        }
 
        /*
         * After all the positive number attnums in stxkeys come the negative
         * numbers (if any) which represent expressions in the order that they
         * appear in stxdexpr.  Because the expressions are always
         * monotonically decreasing from -1, there is no point in looking at
         * the values in stxkeys, it's enough to know how many of them there
         * are.
         */
        for (int i = numattnums; i < numattrs; i++)
        {
            Node       *expr = list_nth(exprs, i - numattnums);
 
            atttypids[i] = exprType(expr);
            atttypmods[i] = exprTypmod(expr);
            atttypcolls[i] = exprCollation(expr);
        }
    }
 
    /*
     * Populate the pg_statistic_ext_data result tuple.
     */
 
    /* Primary Key: cannot be NULL or replaced. */
    values[Anum_pg_statistic_ext_data_stxoid - 1] = ObjectIdGetDatum(stxform->oid);
    nulls[Anum_pg_statistic_ext_data_stxoid - 1] = false;
    values[Anum_pg_statistic_ext_data_stxdinherit - 1] = BoolGetDatum(inherited);
    nulls[Anum_pg_statistic_ext_data_stxdinherit - 1] = false;
 
    /* All unspecified parameters will be left unmodified */
    nulls[Anum_pg_statistic_ext_data_stxdndistinct - 1] = true;
    nulls[Anum_pg_statistic_ext_data_stxddependencies - 1] = true;
    nulls[Anum_pg_statistic_ext_data_stxdmcv - 1] = true;
    nulls[Anum_pg_statistic_ext_data_stxdexpr - 1] = true;
 
    /*
     * For each stats kind, deserialize the data at hand and perform a round
     * of validation.  The resulting tuple is filled with a set of updated
     * values.
     */
 
    if (has.ndistinct)
    {
        Datum       ndistinct_datum = PG_GETARG_DATUM(NDISTINCT_ARG);
        bytea      *data = DatumGetByteaPP(ndistinct_datum);
        MVNDistinct *ndistinct = statext_ndistinct_deserialize(data);
 
        if (statext_ndistinct_validate(ndistinct, &stxform->stxkeys,
                                       numexprs, WARNING))
        {
            values[Anum_pg_statistic_ext_data_stxdndistinct - 1] = ndistinct_datum;
            nulls[Anum_pg_statistic_ext_data_stxdndistinct - 1] = false;
            replaces[Anum_pg_statistic_ext_data_stxdndistinct - 1] = true;
        }
        else
            success = false;
 
        statext_ndistinct_free(ndistinct);
    }
 
    if (has.dependencies)
    {
        Datum       dependencies_datum = PG_GETARG_DATUM(DEPENDENCIES_ARG);
        bytea      *data = DatumGetByteaPP(dependencies_datum);
        MVDependencies *dependencies = statext_dependencies_deserialize(data);
 
        if (statext_dependencies_validate(dependencies, &stxform->stxkeys,
                                          numexprs, WARNING))
        {
            values[Anum_pg_statistic_ext_data_stxddependencies - 1] = dependencies_datum;
            nulls[Anum_pg_statistic_ext_data_stxddependencies - 1] = false;
            replaces[Anum_pg_statistic_ext_data_stxddependencies - 1] = true;
        }
        else
            success = false;
 
        statext_dependencies_free(dependencies);
    }
 
    if (has.mcv)
    {
        Datum       datum;
        bool        val_ok = false;
 
        datum = import_mcv(PG_GETARG_ARRAYTYPE_P(MOST_COMMON_VALS_ARG),
                           PG_GETARG_ARRAYTYPE_P(MOST_COMMON_FREQS_ARG),
                           PG_GETARG_ARRAYTYPE_P(MOST_COMMON_BASE_FREQS_ARG),
                           atttypids, atttypmods, atttypcolls, numattrs,
                           &val_ok);
 
        if (val_ok)
        {
            Assert(datum != (Datum) 0);
            values[Anum_pg_statistic_ext_data_stxdmcv - 1] = datum;
            nulls[Anum_pg_statistic_ext_data_stxdmcv - 1] = false;
            replaces[Anum_pg_statistic_ext_data_stxdmcv - 1] = true;
        }
        else
            success = false;
    }
 
    if (has.expressions)
    {
        Datum       datum;
        Relation    pgsd;
        bool        ok = false;
 
        pgsd = table_open(StatisticRelationId, RowExclusiveLock);
 
        /*
         * Generate the expressions array.
         *
         * The atttypids, atttypmods, and atttypcolls arrays have all the
         * regular attributes listed first, so we can pass those arrays with a
         * start point after the last regular attribute.  There are numexprs
         * elements remaining.
         */
        datum = import_expressions(pgsd, numexprs,
                                   &atttypids[numattnums],
                                   &atttypmods[numattnums],
                                   &atttypcolls[numattnums],
                                   PG_GETARG_JSONB_P(EXPRESSIONS_ARG),
                                   &ok);
 
        table_close(pgsd, RowExclusiveLock);
 
        if (ok)
        {
            Assert(datum != (Datum) 0);
            values[Anum_pg_statistic_ext_data_stxdexpr - 1] = datum;
            replaces[Anum_pg_statistic_ext_data_stxdexpr - 1] = true;
            nulls[Anum_pg_statistic_ext_data_stxdexpr - 1] = false;
        }
        else
            success = false;
    }
 
    upsert_pg_statistic_ext_data(values, nulls, replaces);
 
cleanup:
    if (HeapTupleIsValid(tup))
        heap_freetuple(tup);
    if (pg_stext != NULL)
        table_close(pg_stext, RowExclusiveLock);
    if (atttypids != NULL)
        pfree(atttypids);
    if (atttypmods != NULL)
        pfree(atttypmods);
    if (atttypcolls != NULL)
        pfree(atttypcolls);
    return success;
}
 
/*
 * Consistency checks to ensure that other mcvlist arrays are in alignment
 * with the mcv array.
 */
static bool
check_mcvlist_array(const ArrayType *arr, int argindex, int required_ndims,
                    int mcv_length)
{
    if (ARR_NDIM(arr) != required_ndims)
    {
        ereport(WARNING,
                errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                errmsg("could not parse array \"%s\": incorrect number of dimensions (%d required)",
                       extarginfo[argindex].argname, required_ndims));
        return false;
    }
 
    if (array_contains_nulls(arr))
    {
        ereport(WARNING,
                errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                errmsg("could not parse array \"%s\": NULL value found",
                       extarginfo[argindex].argname));
        return false;
    }
 
    if (ARR_DIMS(arr)[0] != mcv_length)
    {
        ereport(WARNING,
                errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                errmsg("could not parse array \"%s\": incorrect number of elements (same as \"%s\" required)",
                       extarginfo[argindex].argname,
                       extarginfo[MOST_COMMON_VALS_ARG].argname));
        return false;
    }
 
    return true;
}
 
/*
 * Create the stxdmcv datum from the equal-sized arrays of most common values,
 * their null flags, and the frequency and base frequency associated with
 * each value.
 */
static Datum
import_mcv(const ArrayType *mcv_arr, const ArrayType *freqs_arr,
           const ArrayType *base_freqs_arr, Oid *atttypids, int32 *atttypmods,
           Oid *atttypcolls, int numattrs, bool *ok)
{
    int         nitems;
    Datum      *mcv_elems;
    bool       *mcv_nulls;
    int         check_nummcv;
    Datum       mcv = (Datum) 0;
 
    *ok = false;
 
    /*
     * mcv_arr is an array of arrays.  Each inner array must have the same
     * number of elements "numattrs".
     */
    if (ARR_NDIM(mcv_arr) != 2)
    {
        ereport(WARNING,
                errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                errmsg("could not parse array \"%s\": incorrect number of dimensions (%d required)",
                       extarginfo[MOST_COMMON_VALS_ARG].argname, 2));
        goto mcv_error;
    }
 
    if (ARR_DIMS(mcv_arr)[1] != numattrs)
    {
        ereport(WARNING,
                errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                errmsg("could not parse array \"%s\": found %d attributes but expected %d",
                       extarginfo[MOST_COMMON_VALS_ARG].argname,
                       ARR_DIMS(mcv_arr)[1], numattrs));
        goto mcv_error;
    }
 
    /*
     * "most_common_freqs" and "most_common_base_freqs" arrays must be of the
     * same length, one-dimension and cannot contain NULLs.  We use mcv_arr as
     * the reference array for determining their length.
     */
    nitems = ARR_DIMS(mcv_arr)[0];
    if (!check_mcvlist_array(freqs_arr, MOST_COMMON_FREQS_ARG, 1, nitems) ||
        !check_mcvlist_array(base_freqs_arr, MOST_COMMON_BASE_FREQS_ARG, 1, nitems))
    {
        /* inconsistent input arrays found */
        goto mcv_error;
    }
 
    /*
     * This part builds the contents for "most_common_val_nulls", based on the
     * values from "most_common_vals".
     */
    deconstruct_array_builtin(mcv_arr, TEXTOID, &mcv_elems,
                              &mcv_nulls, &check_nummcv);
 
    mcv = statext_mcv_import(WARNING, numattrs,
                             atttypids, atttypmods, atttypcolls,
                             nitems, mcv_elems, mcv_nulls,
                             (float8 *) ARR_DATA_PTR(freqs_arr),
                             (float8 *) ARR_DATA_PTR(base_freqs_arr));
 
    *ok = (mcv != (Datum) 0);
 
mcv_error:
    return mcv;
}
 
/*
 * Check if key is found in the list of expression argnames.
 */
static bool
key_in_expr_argnames(JsonbValue *key)
{
    Assert(key->type == jbvString);
    for (int i = 0; i < NUM_ATTRIBUTE_STATS_ELEMS; i++)
    {
        if (strncmp(extexprargname[i], key->val.string.val, key->val.string.len) == 0)
            return true;
    }
    return false;
}
 
/*
 * Verify that all of the keys in the object are valid argnames.
 */
static bool
check_all_expr_argnames_valid(JsonbContainer *cont, AttrNumber exprnum)
{
    bool        all_keys_valid = true;
 
    JsonbIterator *jbit;
    JsonbIteratorToken jitok;
    JsonbValue  jkey;
 
    Assert(JsonContainerIsObject(cont));
 
    jbit = JsonbIteratorInit(cont);
 
    /* We always start off with a BEGIN OBJECT */
    jitok = JsonbIteratorNext(&jbit, &jkey, false);
    Assert(jitok == WJB_BEGIN_OBJECT);
 
    while (true)
    {
        JsonbValue  jval;
 
        jitok = JsonbIteratorNext(&jbit, &jkey, false);
 
        /*
         * We have run of keys. This is the only condition where it is
         * memory-safe to break out of the loop.
         */
        if (jitok == WJB_END_OBJECT)
            break;
 
        /* We can only find keys inside an object */
        Assert(jitok == WJB_KEY);
        Assert(jkey.type == jbvString);
 
        /* A value must follow the key */
        jitok = JsonbIteratorNext(&jbit, &jval, false);
        Assert(jitok == WJB_VALUE);
 
        /*
         * If we have already found an invalid key, there is no point in
         * looking for more, because additional WARNINGs are just clutter. We
         * must continue iterating over the json to ensure that we clean up
         * all allocated memory.
         */
        if (!all_keys_valid)
            continue;
 
        if (!key_in_expr_argnames(&jkey))
        {
            char       *bad_element_name = jbv_string_get_cstr(&jkey);
 
            ereport(WARNING,
                    errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                    errmsg("could not import element in expression %d: invalid key name",
                           exprnum));
 
            pfree(bad_element_name);
            all_keys_valid = false;
        }
    }
    return all_keys_valid;
}
 
/*
 * Simple conversion of jbvString to cstring
 */
static char *
jbv_string_get_cstr(JsonbValue *jval)
{
    char       *s;
 
    Assert(jval->type == jbvString);
 
    s = palloc0(jval->val.string.len + 1);
    memcpy(s, jval->val.string.val, jval->val.string.len);
 
    return s;
}
 
/*
 * Apply a jbvString value to a safe scalar input function.
 */
static bool
jbv_to_infunc_datum(JsonbValue *jval, PGFunction func, AttrNumber exprnum,
                    const char *argname, Datum *datum)
{
    ErrorSaveContext escontext = {
        .type = T_ErrorSaveContext,
        .details_wanted = true
    };
 
    char       *s = jbv_string_get_cstr(jval);
    bool        ok;
 
    ok = DirectInputFunctionCallSafe(func, s, InvalidOid, -1,
                                     (Node *) &escontext, datum);
 
    /*
     * If we got a type import error, use the report generated and add an
     * error hint before throwing a warning.
     */
    if (!ok)
    {
        StringInfoData hint_str;
 
        initStringInfo(&hint_str);
        appendStringInfo(&hint_str,
                         "Element \"%s\" in expression %d could not be parsed.",
                         argname, exprnum);
 
        escontext.error_data->elevel = WARNING;
        escontext.error_data->hint = hint_str.data;
 
        ThrowErrorData(escontext.error_data);
        pfree(hint_str.data);
    }
 
    pfree(s);
    return ok;
}
 
/*
 * Build an array datum with element type elemtypid from a text datum, used as
 * value of an attribute in a pg_statistic tuple.
 *
 * If an error is encountered, capture it, and reduce the elevel to WARNING.
 *
 * This is an adaptation of statatt_build_stavalues().
 */
static Datum
array_in_safe(FmgrInfo *array_in, const char *s, Oid typid, int32 typmod,
              AttrNumber exprnum, const char *element_name, bool *ok)
{
    LOCAL_FCINFO(fcinfo, 3);
    Datum       result;
 
    ErrorSaveContext escontext = {
        .type = T_ErrorSaveContext,
        .details_wanted = true
    };
 
    *ok = false;
    InitFunctionCallInfoData(*fcinfo, array_in, 3, InvalidOid,
                             (Node *) &escontext, NULL);
 
    fcinfo->args[0].value = CStringGetDatum(s);
    fcinfo->args[0].isnull = false;
    fcinfo->args[1].value = ObjectIdGetDatum(typid);
    fcinfo->args[1].isnull = false;
    fcinfo->args[2].value = Int32GetDatum(typmod);
    fcinfo->args[2].isnull = false;
 
    result = FunctionCallInvoke(fcinfo);
 
    /*
     * If the array_in function returned an error, we will want to report that
     * ERROR as a WARNING, and add some location context to the error message.
     * Overwriting the existing hint (if any) is not ideal, and an error
     * context would only work for level >= ERROR.
     */
    if (escontext.error_occurred)
    {
        StringInfoData hint_str;
 
        initStringInfo(&hint_str);
        appendStringInfo(&hint_str,
                         "Element \"%s\" in expression %d could not be parsed.",
                         element_name, exprnum);
        escontext.error_data->elevel = WARNING;
        escontext.error_data->hint = hint_str.data;
        ThrowErrorData(escontext.error_data);
        pfree(hint_str.data);
        return (Datum) 0;
    }
 
    if (array_contains_nulls(DatumGetArrayTypeP(result)))
    {
        ereport(WARNING,
                errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                errmsg("could not import element \"%s\" in expression %d: null value found",
                       element_name, exprnum));
        return (Datum) 0;
    }
 
    *ok = true;
    return result;
}
 
/*
 * Create a pg_statistic tuple from an expression JSONB container.
 *
 * The pg_statistic tuple is pre-populated with acceptable defaults, therefore
 * even if there is an issue with all of the keys in the container, we can
 * still return a legit tuple datum.
 *
 * Set pg_statistic_ok to true if all of the values found in the container
 * were imported without issue.  pg_statistic_ok is switched to "true" once
 * the full pg_statistic tuple has been built and validated.
 */
static Datum
import_pg_statistic(Relation pgsd, JsonbContainer *cont,
                    AttrNumber exprnum, FmgrInfo *array_in_fn,
                    Oid typid, int32 typmod, Oid typcoll,
                    bool *pg_statistic_ok)
{
    const char *argname = extarginfo[EXPRESSIONS_ARG].argname;
    TypeCacheEntry *typcache;
    Datum       values[Natts_pg_statistic];
    bool        nulls[Natts_pg_statistic];
    bool        replaces[Natts_pg_statistic];
    HeapTuple   pgstup = NULL;
    Datum       pgstdat = (Datum) 0;
    Oid         elemtypid = InvalidOid;
    Oid         elemeqopr = InvalidOid;
    bool        found[NUM_ATTRIBUTE_STATS_ELEMS] = {0};
    JsonbValue  val[NUM_ATTRIBUTE_STATS_ELEMS] = {0};
 
    /* Assume the worst by default. */
    *pg_statistic_ok = false;
 
    if (!JsonContainerIsObject(cont))
    {
        ereport(WARNING,
                errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                errmsg("could not parse \"%s\": invalid element in expression %d",
                       argname, exprnum));
        goto pg_statistic_error;
    }
 
    /*
     * Loop through all keys that we need to look up.  If any value found is
     * neither a string nor a NULL, there is not much we can do, so just give
     * on the entire tuple for this expression.
     */
    for (int i = 0; i < NUM_ATTRIBUTE_STATS_ELEMS; i++)
    {
        const char *s = extexprargname[i];
        int         len = strlen(s);
 
        if (getKeyJsonValueFromContainer(cont, s, len, &val[i]) == NULL)
            continue;
 
        switch (val[i].type)
        {
            case jbvString:
                found[i] = true;
                break;
 
            case jbvNull:
                break;
 
            default:
                ereport(WARNING,
                        errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                        errmsg("could not parse \"%s\": invalid element in expression %d", argname, exprnum),
                        errhint("Value of element \"%s\" must be type a null or a string.", s));
                goto pg_statistic_error;
        }
    }
 
    /* Look for invalid keys */
    if (!check_all_expr_argnames_valid(cont, exprnum))
        goto pg_statistic_error;
 
    /*
     * There are two arg pairs, MCV+MCF and MCEV+MCEF.  Both values must
     * either be found or not be found.  Any disagreement is a warning.  Once
     * we have ruled out disagreeing pairs, we can use either found flag as a
     * proxy for the other.
     */
    if (found[MOST_COMMON_VALS_ELEM] != found[MOST_COMMON_FREQS_ELEM])
    {
        ereport(WARNING,
                errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                errmsg("could not parse \"%s\": invalid element in expression %d",
                       argname, exprnum),
                errhint("\"%s\" and \"%s\" must be both either strings or nulls.",
                        extexprargname[MOST_COMMON_VALS_ELEM],
                        extexprargname[MOST_COMMON_FREQS_ELEM]));
        goto pg_statistic_error;
    }
    if (found[MOST_COMMON_ELEMS_ELEM] != found[MOST_COMMON_ELEM_FREQS_ELEM])
    {
        ereport(WARNING,
                errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                errmsg("could not parse \"%s\": invalid element in expression %d",
                       argname, exprnum),
                errhint("\"%s\" and \"%s\" must be both either strings or nulls.",
                        extexprargname[MOST_COMMON_ELEMS_ELEM],
                        extexprargname[MOST_COMMON_ELEM_FREQS_ELEM]));
        goto pg_statistic_error;
    }
 
    /*
     * Range types may expect three values to be set.  All three of them must
     * either be found or not be found.  Any disagreement is a warning.
     */
    if (found[RANGE_LENGTH_HISTOGRAM_ELEM] != found[RANGE_EMPTY_FRAC_ELEM] ||
        found[RANGE_LENGTH_HISTOGRAM_ELEM] != found[RANGE_BOUNDS_HISTOGRAM_ELEM])
    {
        ereport(WARNING,
                errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                errmsg("could not parse \"%s\": invalid element in expression %d",
                       argname, exprnum),
                errhint("\"%s\", \"%s\", and \"%s\" must be all either strings or all nulls.",
                        extexprargname[RANGE_LENGTH_HISTOGRAM_ELEM],
                        extexprargname[RANGE_EMPTY_FRAC_ELEM],
                        extexprargname[RANGE_BOUNDS_HISTOGRAM_ELEM]));
        goto pg_statistic_error;
    }
 
    /* This finds the right operators even if atttypid is a domain */
    typcache = lookup_type_cache(typid, TYPECACHE_LT_OPR | TYPECACHE_EQ_OPR);
 
    statatt_init_empty_tuple(InvalidOid, InvalidAttrNumber, false,
                             values, nulls, replaces);
 
    /*
     * Special case: collation for tsvector is DEFAULT_COLLATION_OID. See
     * compute_tsvector_stats().
     */
    if (typid == TSVECTOROID)
        typcoll = DEFAULT_COLLATION_OID;
 
    /*
     * We only need to fetch element type and eq operator if we have a stat of
     * type MCELEM or DECHIST, otherwise the values are unnecessary and not
     * meaningful.
     */
    if (found[MOST_COMMON_ELEMS_ELEM] || found[ELEM_COUNT_HISTOGRAM_ELEM])
    {
        if (!statatt_get_elem_type(typid, typcache->typtype,
                                   &elemtypid, &elemeqopr))
        {
            ereport(WARNING,
                    errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                    errmsg("could not parse \"%s\": invalid element type in expression %d",
                           argname, exprnum));
            goto pg_statistic_error;
        }
    }
 
    /*
     * These three fields can only be set if dealing with a range or
     * multi-range type.
     */
    if (found[RANGE_LENGTH_HISTOGRAM_ELEM] ||
        found[RANGE_EMPTY_FRAC_ELEM] ||
        found[RANGE_BOUNDS_HISTOGRAM_ELEM])
    {
        if (typcache->typtype != TYPTYPE_RANGE &&
            typcache->typtype != TYPTYPE_MULTIRANGE)
        {
            ereport(WARNING,
                    errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                    errmsg("could not parse \"%s\": invalid data in expression %d",
                           argname, exprnum),
                    errhint("\"%s\", \"%s\", and \"%s\" can only be set for a range type.",
                            extexprargname[RANGE_LENGTH_HISTOGRAM_ELEM],
                            extexprargname[RANGE_EMPTY_FRAC_ELEM],
                            extexprargname[RANGE_BOUNDS_HISTOGRAM_ELEM]));
            goto pg_statistic_error;
        }
    }
 
    /* null_frac */
    if (found[NULL_FRAC_ELEM])
    {
        Datum       datum;
 
        if (jbv_to_infunc_datum(&val[NULL_FRAC_ELEM], float4in, exprnum,
                                extexprargname[NULL_FRAC_ELEM], &datum))
            values[Anum_pg_statistic_stanullfrac - 1] = datum;
        else
            goto pg_statistic_error;
    }
 
    /* avg_width */
    if (found[AVG_WIDTH_ELEM])
    {
        Datum       datum;
 
        if (jbv_to_infunc_datum(&val[AVG_WIDTH_ELEM], int4in, exprnum,
                                extexprargname[AVG_WIDTH_ELEM], &datum))
            values[Anum_pg_statistic_stawidth - 1] = datum;
        else
            goto pg_statistic_error;
    }
 
    /* n_distinct */
    if (found[N_DISTINCT_ELEM])
    {
        Datum       datum;
 
        if (jbv_to_infunc_datum(&val[N_DISTINCT_ELEM], float4in, exprnum,
                                extexprargname[N_DISTINCT_ELEM], &datum))
            values[Anum_pg_statistic_stadistinct - 1] = datum;
        else
            goto pg_statistic_error;
    }
 
    /*
     * The STAKIND statistics are the same as the ones found in attribute
     * stats.  However, these are all derived from json strings, whereas the
     * ones derived for attribute stats are a mix of datatypes.  This limits
     * the opportunities for code sharing between the two.
     *
     * Some statistic kinds have both a stanumbers and a stavalues components.
     * In those cases, both values must either be NOT NULL or both NULL, and
     * if they aren't then we need to reject that stakind completely.
     * Currently we go a step further and reject the expression array
     * completely.
     */
 
    if (found[MOST_COMMON_VALS_ELEM])
    {
        Datum       stavalues;
        Datum       stanumbers;
        bool        val_ok = false;
        bool        num_ok = false;
        char       *s;
 
        s = jbv_string_get_cstr(&val[MOST_COMMON_VALS_ELEM]);
        stavalues = array_in_safe(array_in_fn, s, typid, typmod, exprnum,
                                  extexprargname[MOST_COMMON_VALS_ELEM],
                                  &val_ok);
 
        pfree(s);
 
        s = jbv_string_get_cstr(&val[MOST_COMMON_FREQS_ELEM]);
        stanumbers = array_in_safe(array_in_fn, s, FLOAT4OID, -1, exprnum,
                                   extexprargname[MOST_COMMON_FREQS_ELEM],
                                   &num_ok);
        pfree(s);
 
        /* Only set the slot if both datums have been built */
        if (val_ok && num_ok)
            statatt_set_slot(values, nulls, replaces,
                             STATISTIC_KIND_MCV,
                             typcache->eq_opr, typcoll,
                             stanumbers, false, stavalues, false);
        else
            goto pg_statistic_error;
    }
 
    /* STATISTIC_KIND_HISTOGRAM */
    if (found[HISTOGRAM_BOUNDS_ELEM])
    {
        Datum       stavalues;
        bool        val_ok = false;
        char       *s = jbv_string_get_cstr(&val[HISTOGRAM_BOUNDS_ELEM]);
 
        stavalues = array_in_safe(array_in_fn, s, typid, typmod, exprnum,
                                  extexprargname[HISTOGRAM_BOUNDS_ELEM],
                                  &val_ok);
        pfree(s);
 
        if (val_ok)
            statatt_set_slot(values, nulls, replaces,
                             STATISTIC_KIND_HISTOGRAM,
                             typcache->lt_opr, typcoll,
                             0, true, stavalues, false);
        else
            goto pg_statistic_error;
    }
 
    /* STATISTIC_KIND_CORRELATION */
    if (found[CORRELATION_ELEM])
    {
        Datum       corr[] = {(Datum) 0};
 
        if (jbv_to_infunc_datum(&val[CORRELATION_ELEM], float4in, exprnum,
                                extexprargname[CORRELATION_ELEM], &corr[0]))
        {
            ArrayType  *arry = construct_array_builtin(corr, 1, FLOAT4OID);
            Datum       stanumbers = PointerGetDatum(arry);
 
            statatt_set_slot(values, nulls, replaces,
                             STATISTIC_KIND_CORRELATION,
                             typcache->lt_opr, typcoll,
                             stanumbers, false, 0, true);
        }
        else
            goto pg_statistic_error;
    }
 
    /* STATISTIC_KIND_MCELEM */
    if (found[MOST_COMMON_ELEMS_ELEM])
    {
        Datum       stavalues;
        Datum       stanumbers;
        bool        val_ok = false;
        bool        num_ok = false;
        char       *s;
 
        s = jbv_string_get_cstr(&val[MOST_COMMON_ELEMS_ELEM]);
        stavalues = array_in_safe(array_in_fn, s, elemtypid, typmod, exprnum,
                                  extexprargname[MOST_COMMON_ELEMS_ELEM],
                                  &val_ok);
        pfree(s);
 
 
        s = jbv_string_get_cstr(&val[MOST_COMMON_ELEM_FREQS_ELEM]);
        stanumbers = array_in_safe(array_in_fn, s, FLOAT4OID, -1, exprnum,
                                   extexprargname[MOST_COMMON_ELEM_FREQS_ELEM],
                                   &num_ok);
        pfree(s);
 
        /* Only set the slot if both datums have been built */
        if (val_ok && num_ok)
            statatt_set_slot(values, nulls, replaces,
                             STATISTIC_KIND_MCELEM,
                             elemeqopr, typcoll,
                             stanumbers, false, stavalues, false);
        else
            goto pg_statistic_error;
    }
 
    /* STATISTIC_KIND_DECHIST */
    if (found[ELEM_COUNT_HISTOGRAM_ELEM])
    {
        Datum       stanumbers;
        bool        num_ok = false;
        char       *s;
 
        s = jbv_string_get_cstr(&val[ELEM_COUNT_HISTOGRAM_ELEM]);
        stanumbers = array_in_safe(array_in_fn, s, FLOAT4OID, -1, exprnum,
                                   extexprargname[ELEM_COUNT_HISTOGRAM_ELEM],
                                   &num_ok);
        pfree(s);
 
        if (num_ok)
            statatt_set_slot(values, nulls, replaces, STATISTIC_KIND_DECHIST,
                             elemeqopr, typcoll, stanumbers, false, 0, true);
        else
            goto pg_statistic_error;
    }
 
    /*
     * STATISTIC_KIND_BOUNDS_HISTOGRAM
     *
     * This stakind appears before STATISTIC_KIND_RANGE_LENGTH_HISTOGRAM even
     * though it is numerically greater, and all other stakinds appear in
     * numerical order.
     */
    if (found[RANGE_BOUNDS_HISTOGRAM_ELEM])
    {
        Datum       stavalues;
        bool        val_ok = false;
        char       *s;
        Oid         rtypid = typid;
 
        /*
         * If it's a multirange, step down to the range type, as is done by
         * multirange_typanalyze().
         */
        if (type_is_multirange(typid))
            rtypid = get_multirange_range(typid);
 
        s = jbv_string_get_cstr(&val[RANGE_BOUNDS_HISTOGRAM_ELEM]);
 
        stavalues = array_in_safe(array_in_fn, s, rtypid, typmod, exprnum,
                                  extexprargname[RANGE_BOUNDS_HISTOGRAM_ELEM],
                                  &val_ok);
 
        if (val_ok)
            statatt_set_slot(values, nulls, replaces,
                             STATISTIC_KIND_BOUNDS_HISTOGRAM,
                             InvalidOid, InvalidOid,
                             0, true, stavalues, false);
        else
            goto pg_statistic_error;
    }
 
    /* STATISTIC_KIND_RANGE_LENGTH_HISTOGRAM */
    if (found[RANGE_LENGTH_HISTOGRAM_ELEM])
    {
        Datum       empty_frac[] = {(Datum) 0};
        Datum       stavalues;
        Datum       stanumbers;
        bool        val_ok = false;
        char       *s;
 
        if (jbv_to_infunc_datum(&val[RANGE_EMPTY_FRAC_ELEM], float4in, exprnum,
                                extexprargname[RANGE_EMPTY_FRAC_ELEM], &empty_frac[0]))
        {
            ArrayType  *arry = construct_array_builtin(empty_frac, 1, FLOAT4OID);
 
            stanumbers = PointerGetDatum(arry);
        }
        else
            goto pg_statistic_error;
 
        s = jbv_string_get_cstr(&val[RANGE_LENGTH_HISTOGRAM_ELEM]);
        stavalues = array_in_safe(array_in_fn, s, FLOAT8OID, -1, exprnum,
                                  extexprargname[RANGE_LENGTH_HISTOGRAM_ELEM],
                                  &val_ok);
 
        if (val_ok)
            statatt_set_slot(values, nulls, replaces,
                             STATISTIC_KIND_RANGE_LENGTH_HISTOGRAM,
                             Float8LessOperator, InvalidOid,
                             stanumbers, false, stavalues, false);
        else
            goto pg_statistic_error;
    }
 
    pgstup = heap_form_tuple(RelationGetDescr(pgsd), values, nulls);
    pgstdat = heap_copy_tuple_as_datum(pgstup, RelationGetDescr(pgsd));
 
    heap_freetuple(pgstup);
 
    *pg_statistic_ok = true;
 
    return pgstdat;
 
pg_statistic_error:
    return (Datum) 0;
}
 
/*
 * Create the stxdexpr datum, which is an array of pg_statistic rows with all
 * of the object identification fields left at defaults, using the json array
 * of objects/nulls referenced against the datatypes for the expressions.
 *
 * The exprs_is_perfect will be set to true if all pg_statistic rows were
 * imported cleanly.  If any of them experienced a problem (and thus were
 * set as if they were null), then the expression is kept but exprs_is_perfect
 * will be marked as false.
 *
 * This datum is needed to fill out a complete pg_statistic_ext_data tuple.
 */
static Datum
import_expressions(Relation pgsd, int numexprs,
                   Oid *atttypids, int32 *atttypmods,
                   Oid *atttypcolls, Jsonb *exprs_jsonb,
                   bool *exprs_is_perfect)
{
    const char *argname = extarginfo[EXPRESSIONS_ARG].argname;
    Oid         pgstypoid = get_rel_type_id(StatisticRelationId);
    ArrayBuildState *astate = NULL;
    Datum       result = (Datum) 0;
    int         num_import_ok = 0;
    JsonbContainer *root;
    int         num_root_elements;
 
    FmgrInfo    array_in_fn;
 
    *exprs_is_perfect = false;
 
    /* Json schema must be [{expr},...] */
    if (!JB_ROOT_IS_ARRAY(exprs_jsonb))
    {
        ereport(WARNING,
                errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                errmsg("could not parse \"%s\": root-level array required", argname));
        goto exprs_error;
    }
 
    root = &exprs_jsonb->root;
 
    /*
     * The number of elements in the array must match the number of
     * expressions in the stats object definition.
     */
    num_root_elements = JsonContainerSize(root);
    if (numexprs != num_root_elements)
    {
        ereport(WARNING,
                errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                errmsg("could not parse \"%s\": incorrect number of elements (%d required)",
                       argname, num_root_elements));
        goto exprs_error;
    }
 
    fmgr_info(F_ARRAY_IN, &array_in_fn);
 
    /*
     * Iterate over each expected expression object in the array.  Some of
     * them could be null.  If the element is a completely wrong data type,
     * give a WARNING and then treat the element like a NULL element in the
     * result array.
     *
     * Each expression *MUST* have a value appended in the result pg_statistic
     * array.
     */
    for (int i = 0; i < numexprs; i++)
    {
        Datum       pgstdat = (Datum) 0;
        bool        isnull = false;
        AttrNumber  exprattnum = -1 - i;
 
        JsonbValue *elem = getIthJsonbValueFromContainer(root, i);
 
        switch (elem->type)
        {
            case jbvBinary:
                {
                    bool        sta_ok = false;
 
                    /* a real stats object */
                    pgstdat = import_pg_statistic(pgsd, elem->val.binary.data,
                                                  exprattnum, &array_in_fn,
                                                  atttypids[i], atttypmods[i],
                                                  atttypcolls[i], &sta_ok);
 
                    /*
                     * If some incorrect data has been found, assign NULL for
                     * this expression as a mean to give up.
                     */
                    if (sta_ok)
                        num_import_ok++;
                    else
                    {
                        isnull = true;
                        pgstdat = (Datum) 0;
                    }
                }
                break;
 
            case jbvNull:
                /* NULL placeholder for invalid data, still fine */
                isnull = true;
                num_import_ok++;
                break;
 
            default:
                /* cannot possibly be valid */
                ereport(WARNING,
                        errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                        errmsg("could not parse \"%s\": invalid element in expression %d",
                               argname, exprattnum));
                goto exprs_error;
        }
 
        astate = accumArrayResult(astate, pgstdat, isnull, pgstypoid,
                                  CurrentMemoryContext);
    }
 
    /*
     * The expressions datum is perfect *if and only if* all of the
     * pg_statistic elements were also ok, for a number of elements equal to
     * the number of expressions.  Anything else means a failure in restoring
     * the data of this statistics object.
     */
    *exprs_is_perfect = (num_import_ok == numexprs);
 
    if (astate != NULL)
        result = makeArrayResult(astate, CurrentMemoryContext);
 
    return result;
 
exprs_error:
    if (astate != NULL)
        pfree(astate);
    return (Datum) 0;
};
 
/*
 * Remove an existing pg_statistic_ext_data row for a given pg_statistic_ext
 * row and "inherited" pair.
 */
static bool
delete_pg_statistic_ext_data(Oid stxoid, bool inherited)
{
    Relation    sed = table_open(StatisticExtDataRelationId, RowExclusiveLock);
    HeapTuple   oldtup;
    bool        result = false;
 
    /* Is there already a pg_statistic_ext_data tuple for this attribute? */
    oldtup = SearchSysCache2(STATEXTDATASTXOID,
                             ObjectIdGetDatum(stxoid),
                             BoolGetDatum(inherited));
 
    if (HeapTupleIsValid(oldtup))
    {
        CatalogTupleDelete(sed, &oldtup->t_self);
        ReleaseSysCache(oldtup);
        result = true;
    }
 
    table_close(sed, RowExclusiveLock);
 
    CommandCounterIncrement();
 
    return result;
}
 
/*
 * Restore (insert or replace) statistics for the given statistics object.
 *
 * This function accepts variadic arguments in key-value pairs, which are
 * given to stats_fill_fcinfo_from_arg_pairs to be mapped into positional
 * arguments.
 */
Datum
pg_restore_extended_stats(PG_FUNCTION_ARGS)
{
    LOCAL_FCINFO(positional_fcinfo, NUM_EXTENDED_STATS_ARGS);
    bool        result = true;
 
    InitFunctionCallInfoData(*positional_fcinfo, NULL, NUM_EXTENDED_STATS_ARGS,
                             InvalidOid, NULL, NULL);
 
    if (!stats_fill_fcinfo_from_arg_pairs(fcinfo, positional_fcinfo, extarginfo))
        result = false;
 
    if (!extended_statistics_update(positional_fcinfo))
        result = false;
 
    PG_RETURN_BOOL(result);
}
 
/*
 * Delete statistics for the given statistics object.
 */
Datum
pg_clear_extended_stats(PG_FUNCTION_ARGS)
{
    char       *relnspname;
    char       *relname;
    char       *nspname;
    Oid         nspoid;
    Oid         relid;
    char       *stxname;
    bool        inherited;
    Relation    pg_stext;
    HeapTuple   tup;
    Form_pg_statistic_ext stxform;
    Oid         locked_table = InvalidOid;
 
    /* relation arguments */
    stats_check_required_arg(fcinfo, extarginfo, RELSCHEMA_ARG);
    relnspname = TextDatumGetCString(PG_GETARG_DATUM(RELSCHEMA_ARG));
    stats_check_required_arg(fcinfo, extarginfo, RELNAME_ARG);
    relname = TextDatumGetCString(PG_GETARG_DATUM(RELNAME_ARG));
 
    /* extended statistics arguments */
    stats_check_required_arg(fcinfo, extarginfo, STATSCHEMA_ARG);
    nspname = TextDatumGetCString(PG_GETARG_DATUM(STATSCHEMA_ARG));
    stats_check_required_arg(fcinfo, extarginfo, STATNAME_ARG);
    stxname = TextDatumGetCString(PG_GETARG_DATUM(STATNAME_ARG));
    stats_check_required_arg(fcinfo, extarginfo, INHERITED_ARG);
    inherited = PG_GETARG_BOOL(INHERITED_ARG);
 
    if (RecoveryInProgress())
    {
        ereport(WARNING,
                errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
                errmsg("recovery is in progress"),
                errhint("Statistics cannot be modified during recovery."));
        PG_RETURN_VOID();
    }
 
    /*
     * First open the relation where we expect to find the statistics.  This
     * is similar to relation and attribute statistics, so as ACL checks are
     * done before any locks are taken, even before any attempts related to
     * the extended stats object.
     */
    relid = RangeVarGetRelidExtended(makeRangeVar(relnspname, relname, -1),
                                     ShareUpdateExclusiveLock, 0,
                                     RangeVarCallbackForStats, &locked_table);
 
    /* Now check if the namespace of the stats object exists. */
    nspoid = get_namespace_oid(nspname, true);
    if (nspoid == InvalidOid)
    {
        ereport(WARNING,
                errcode(ERRCODE_UNDEFINED_OBJECT),
                errmsg("could not find schema \"%s\"", nspname));
        PG_RETURN_VOID();
    }
 
    pg_stext = table_open(StatisticExtRelationId, RowExclusiveLock);
    tup = get_pg_statistic_ext(pg_stext, nspoid, stxname);
 
    if (!HeapTupleIsValid(tup))
    {
        table_close(pg_stext, RowExclusiveLock);
        ereport(WARNING,
                errcode(ERRCODE_UNDEFINED_OBJECT),
                errmsg("could not find extended statistics object \"%s.%s\"",
                       nspname, stxname));
        PG_RETURN_VOID();
    }
 
    stxform = (Form_pg_statistic_ext) GETSTRUCT(tup);
 
    /*
     * This should be consistent, based on the lock taken on the table when we
     * started.
     */
    if (stxform->stxrelid != relid)
    {
        table_close(pg_stext, RowExclusiveLock);
        ereport(WARNING,
                errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                errmsg("could not clear extended statistics object \"%s.%s\": incorrect relation \"%s.%s\" specified",
                       get_namespace_name(nspoid), stxname,
                       relnspname, relname));
        PG_RETURN_VOID();
    }
 
    delete_pg_statistic_ext_data(stxform->oid, inherited);
    heap_freetuple(tup);
 
    table_close(pg_stext, RowExclusiveLock);
 
    PG_RETURN_VOID();
}