stat_utils.c

Go to the documentation of this file.

/*-------------------------------------------------------------------------
 * stat_utils.c
 *
 *    PostgreSQL statistics manipulation utilities.
 *
 * Code supporting the direct manipulation of statistics.
 *
 * Portions Copyright (c) 1996-2026, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * IDENTIFICATION
 *       src/backend/statistics/stat_utils.c
 *
 *-------------------------------------------------------------------------
 */
 
#include "postgres.h"
 
#include "access/htup_details.h"
#include "access/relation.h"
#include "catalog/index.h"
#include "catalog/namespace.h"
#include "catalog/pg_class.h"
#include "catalog/pg_collation.h"
#include "catalog/pg_database.h"
#include "catalog/pg_statistic.h"
#include "funcapi.h"
#include "miscadmin.h"
#include "nodes/nodeFuncs.h"
#include "statistics/stat_utils.h"
#include "storage/lmgr.h"
#include "utils/acl.h"
#include "utils/array.h"
#include "utils/builtins.h"
#include "utils/lsyscache.h"
#include "utils/rangetypes.h"
#include "utils/rel.h"
#include "utils/syscache.h"
#include "utils/typcache.h"
 
/* Default values assigned to new pg_statistic tuples. */
#define DEFAULT_STATATT_NULL_FRAC      Float4GetDatum(0.0)  /* stanullfrac */
#define DEFAULT_STATATT_AVG_WIDTH      Int32GetDatum(0) /* stawidth, same as
                                                         * unknown */
#define DEFAULT_STATATT_N_DISTINCT     Float4GetDatum(0.0)  /* stadistinct, same as
                                                             * unknown */
 
static Node *statatt_get_index_expr(Relation rel, int attnum);
 
/*
 * Ensure that a given argument is not null.
 */
void
stats_check_required_arg(FunctionCallInfo fcinfo,
                         struct StatsArgInfo *arginfo,
                         int argnum)
{
    if (PG_ARGISNULL(argnum))
        ereport(ERROR,
                (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                 errmsg("argument \"%s\" must not be null",
                        arginfo[argnum].argname)));
}
 
/*
 * Check that argument is either NULL or a one dimensional array with no
 * NULLs.
 *
 * If a problem is found, emit a WARNING, and return false. Otherwise return
 * true.
 */
bool
stats_check_arg_array(FunctionCallInfo fcinfo,
                      struct StatsArgInfo *arginfo,
                      int argnum)
{
    ArrayType  *arr;
 
    if (PG_ARGISNULL(argnum))
        return true;
 
    arr = DatumGetArrayTypeP(PG_GETARG_DATUM(argnum));
 
    if (ARR_NDIM(arr) != 1)
    {
        ereport(WARNING,
                (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                 errmsg("argument \"%s\" must not be a multidimensional array",
                        arginfo[argnum].argname)));
        return false;
    }
 
    if (array_contains_nulls(arr))
    {
        ereport(WARNING,
                (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                 errmsg("argument \"%s\" array must not contain null values",
                        arginfo[argnum].argname)));
        return false;
    }
 
    return true;
}
 
/*
 * Enforce parameter pairs that must be specified together (or not at all) for
 * a particular stakind, such as most_common_vals and most_common_freqs for
 * STATISTIC_KIND_MCV.
 *
 * If a problem is found, emit a WARNING, and return false. Otherwise return
 * true.
 */
bool
stats_check_arg_pair(FunctionCallInfo fcinfo,
                     struct StatsArgInfo *arginfo,
                     int argnum1, int argnum2)
{
    if (PG_ARGISNULL(argnum1) && PG_ARGISNULL(argnum2))
        return true;
 
    if (PG_ARGISNULL(argnum1) || PG_ARGISNULL(argnum2))
    {
        int         nullarg = PG_ARGISNULL(argnum1) ? argnum1 : argnum2;
        int         otherarg = PG_ARGISNULL(argnum1) ? argnum2 : argnum1;
 
        ereport(WARNING,
                (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                 errmsg("argument \"%s\" must be specified when argument \"%s\" is specified",
                        arginfo[nullarg].argname,
                        arginfo[otherarg].argname)));
 
        return false;
    }
 
    return true;
}
 
/*
 * A role has privileges to set statistics on the relation if any of the
 * following are true:
 *   - the role owns the current database and the relation is not shared
 *   - the role has the MAINTAIN privilege on the relation
 */
void
RangeVarCallbackForStats(const RangeVar *relation,
                         Oid relId, Oid oldRelId, void *arg)
{
    Oid        *locked_oid = (Oid *) arg;
    Oid         table_oid = relId;
    HeapTuple   tuple;
    Form_pg_class form;
    char        relkind;
 
    /*
     * If we previously locked some other index's heap, and the name we're
     * looking up no longer refers to that relation, release the now-useless
     * lock.
     */
    if (relId != oldRelId && OidIsValid(*locked_oid))
    {
        UnlockRelationOid(*locked_oid, ShareUpdateExclusiveLock);
        *locked_oid = InvalidOid;
    }
 
    /* If the relation does not exist, there's nothing more to do. */
    if (!OidIsValid(relId))
        return;
 
    /* If the relation does exist, check whether it's an index. */
    relkind = get_rel_relkind(relId);
    if (relkind == RELKIND_INDEX ||
        relkind == RELKIND_PARTITIONED_INDEX)
        table_oid = IndexGetRelation(relId, false);
 
    /*
     * If retrying yields the same OID, there are a couple of extremely
     * unlikely scenarios we need to handle.
     */
    if (relId == oldRelId)
    {
        /*
         * If a previous lookup found an index, but the current lookup did
         * not, the index was dropped and the OID was reused for something
         * else between lookups.  In theory, we could simply drop our lock on
         * the index's parent table and proceed, but in the interest of
         * avoiding complexity, we just error.
         */
        if (table_oid == relId && OidIsValid(*locked_oid))
            ereport(ERROR,
                    (errcode(ERRCODE_UNDEFINED_OBJECT),
                     errmsg("index \"%s\" was concurrently dropped",
                            relation->relname)));
 
        /*
         * If the current lookup found an index but a previous lookup either
         * did not find an index or found one with a different parent
         * relation, the relation was dropped and the OID was reused for an
         * index between lookups.  RangeVarGetRelidExtended() will have
         * already locked the index at this point, so we can't just lock the
         * newly discovered parent table OID without risking deadlock.  As
         * above, we just error in this case.
         */
        if (table_oid != relId && table_oid != *locked_oid)
            ereport(ERROR,
                    (errcode(ERRCODE_UNDEFINED_OBJECT),
                     errmsg("index \"%s\" was concurrently created",
                            relation->relname)));
    }
 
    tuple = SearchSysCache1(RELOID, ObjectIdGetDatum(table_oid));
    if (!HeapTupleIsValid(tuple))
        elog(ERROR, "cache lookup failed for OID %u", table_oid);
    form = (Form_pg_class) GETSTRUCT(tuple);
 
    /* the relkinds that can be used with ANALYZE */
    switch (form->relkind)
    {
        case RELKIND_RELATION:
        case RELKIND_MATVIEW:
        case RELKIND_FOREIGN_TABLE:
        case RELKIND_PARTITIONED_TABLE:
            break;
        default:
            ereport(ERROR,
                    (errcode(ERRCODE_WRONG_OBJECT_TYPE),
                     errmsg("cannot modify statistics for relation \"%s\"",
                            NameStr(form->relname)),
                     errdetail_relkind_not_supported(form->relkind)));
    }
 
    if (form->relisshared)
        ereport(ERROR,
                (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                 errmsg("cannot modify statistics for shared relation")));
 
    /* Check permissions */
    if (!object_ownercheck(DatabaseRelationId, MyDatabaseId, GetUserId()))
    {
        AclResult   aclresult = pg_class_aclcheck(table_oid,
                                                  GetUserId(),
                                                  ACL_MAINTAIN);
 
        if (aclresult != ACLCHECK_OK)
            aclcheck_error(aclresult,
                           get_relkind_objtype(form->relkind),
                           NameStr(form->relname));
    }
 
    ReleaseSysCache(tuple);
 
    /* Lock heap before index to avoid deadlock. */
    if (relId != oldRelId && table_oid != relId)
    {
        LockRelationOid(table_oid, ShareUpdateExclusiveLock);
        *locked_oid = table_oid;
    }
}
 
 
/*
 * Find the argument number for the given argument name, returning -1 if not
 * found.
 */
static int
get_arg_by_name(const char *argname, struct StatsArgInfo *arginfo)
{
    int         argnum;
 
    for (argnum = 0; arginfo[argnum].argname != NULL; argnum++)
        if (pg_strcasecmp(argname, arginfo[argnum].argname) == 0)
            return argnum;
 
    ereport(WARNING,
            (errmsg("unrecognized argument name: \"%s\"", argname)));
 
    return -1;
}
 
/*
 * Ensure that a given argument matched the expected type.
 */
static bool
stats_check_arg_type(const char *argname, Oid argtype, Oid expectedtype)
{
    if (argtype != expectedtype)
    {
        ereport(WARNING,
                (errmsg("argument \"%s\" has type %s, expected type %s",
                        argname, format_type_be(argtype),
                        format_type_be(expectedtype))));
        return false;
    }
 
    return true;
}
 
/*
 * Check if attribute of an index is an expression, then retrieve the
 * expression if is it the case.
 *
 * If the attnum specified is known to be an expression, then we must
 * walk the list attributes up to the specified attnum to get the right
 * expression.
 */
static Node *
statatt_get_index_expr(Relation rel, int attnum)
{
    List       *index_exprs;
    ListCell   *indexpr_item;
 
    /* relation is not an index */
    if (rel->rd_rel->relkind != RELKIND_INDEX &&
        rel->rd_rel->relkind != RELKIND_PARTITIONED_INDEX)
        return NULL;
 
    index_exprs = RelationGetIndexExpressions(rel);
 
    /* index has no expressions to give */
    if (index_exprs == NIL)
        return NULL;
 
    /*
     * The index's attnum points directly to a relation attnum, hence it is
     * not an expression attribute.
     */
    if (rel->rd_index->indkey.values[attnum - 1] != 0)
        return NULL;
 
    indexpr_item = list_head(rel->rd_indexprs);
 
    for (int i = 0; i < attnum - 1; i++)
        if (rel->rd_index->indkey.values[i] == 0)
            indexpr_item = lnext(rel->rd_indexprs, indexpr_item);
 
    if (indexpr_item == NULL)   /* shouldn't happen */
        elog(ERROR, "too few entries in indexprs list");
 
    return (Node *) lfirst(indexpr_item);
}
 
/*
 * Translate variadic argument pairs from 'pairs_fcinfo' into a
 * 'positional_fcinfo' appropriate for calling relation_statistics_update() or
 * attribute_statistics_update() with positional arguments.
 *
 * Caller should have already initialized positional_fcinfo with a size
 * appropriate for calling the intended positional function, and arginfo
 * should also match the intended positional function.
 */
bool
stats_fill_fcinfo_from_arg_pairs(FunctionCallInfo pairs_fcinfo,
                                 FunctionCallInfo positional_fcinfo,
                                 struct StatsArgInfo *arginfo)
{
    Datum      *args;
    bool       *argnulls;
    Oid        *types;
    int         nargs;
    bool        result = true;
 
    /* clear positional args */
    for (int i = 0; arginfo[i].argname != NULL; i++)
    {
        positional_fcinfo->args[i].value = (Datum) 0;
        positional_fcinfo->args[i].isnull = true;
    }
 
    nargs = extract_variadic_args(pairs_fcinfo, 0, true,
                                  &args, &types, &argnulls);
 
    if (nargs % 2 != 0)
        ereport(ERROR,
                errmsg("variadic arguments must be name/value pairs"),
                errhint("Provide an even number of variadic arguments that can be divided into pairs."));
 
    /*
     * For each argument name/value pair, find corresponding positional
     * argument for the argument name, and assign the argument value to
     * positional_fcinfo.
     */
    for (int i = 0; i < nargs; i += 2)
    {
        int         argnum;
        char       *argname;
 
        if (argnulls[i])
            ereport(ERROR,
                    (errmsg("name at variadic position %d is null", i + 1)));
 
        if (types[i] != TEXTOID)
            ereport(ERROR,
                    (errmsg("name at variadic position %d has type %s, expected type %s",
                            i + 1, format_type_be(types[i]),
                            format_type_be(TEXTOID))));
 
        if (argnulls[i + 1])
            continue;
 
        argname = TextDatumGetCString(args[i]);
 
        /*
         * The 'version' argument is a special case, not handled by arginfo
         * because it's not a valid positional argument.
         *
         * For now, 'version' is accepted but ignored. In the future it can be
         * used to interpret older statistics properly.
         */
        if (pg_strcasecmp(argname, "version") == 0)
            continue;
 
        argnum = get_arg_by_name(argname, arginfo);
 
        if (argnum < 0 || !stats_check_arg_type(argname, types[i + 1],
                                                arginfo[argnum].argtype))
        {
            result = false;
            continue;
        }
 
        positional_fcinfo->args[argnum].value = args[i + 1];
        positional_fcinfo->args[argnum].isnull = false;
    }
 
    return result;
}
 
/*
 * Derive type information from a relation attribute.
 *
 * This is needed for setting most slot statistics for all data types.
 *
 * This duplicates the logic in examine_attribute() but it will not skip the
 * attribute if the attstattarget is 0.
 *
 * This information, retrieved from pg_attribute and pg_type with some
 * specific handling for index expressions, is a prerequisite to calling
 * any of the other statatt_*() functions.
 */
void
statatt_get_type(Oid reloid, AttrNumber attnum,
                 Oid *atttypid, int32 *atttypmod,
                 char *atttyptype, Oid *atttypcoll,
                 Oid *eq_opr, Oid *lt_opr)
{
    Relation    rel = relation_open(reloid, AccessShareLock);
    Form_pg_attribute attr;
    HeapTuple   atup;
    Node       *expr;
    TypeCacheEntry *typcache;
 
    atup = SearchSysCache2(ATTNUM, ObjectIdGetDatum(reloid),
                           Int16GetDatum(attnum));
 
    /* Attribute not found */
    if (!HeapTupleIsValid(atup))
        ereport(ERROR,
                (errcode(ERRCODE_UNDEFINED_COLUMN),
                 errmsg("column %d of relation \"%s\" does not exist",
                        attnum, RelationGetRelationName(rel))));
 
    attr = (Form_pg_attribute) GETSTRUCT(atup);
 
    if (attr->attisdropped)
        ereport(ERROR,
                (errcode(ERRCODE_UNDEFINED_COLUMN),
                 errmsg("column %d of relation \"%s\" does not exist",
                        attnum, RelationGetRelationName(rel))));
 
    expr = statatt_get_index_expr(rel, attr->attnum);
 
    /*
     * When analyzing an expression index, believe the expression tree's type
     * not the column datatype --- the latter might be the opckeytype storage
     * type of the opclass, which is not interesting for our purposes.  This
     * mimics the behavior of examine_attribute().
     */
    if (expr == NULL)
    {
        *atttypid = attr->atttypid;
        *atttypmod = attr->atttypmod;
        *atttypcoll = attr->attcollation;
    }
    else
    {
        *atttypid = exprType(expr);
        *atttypmod = exprTypmod(expr);
 
        if (OidIsValid(attr->attcollation))
            *atttypcoll = attr->attcollation;
        else
            *atttypcoll = exprCollation(expr);
    }
    ReleaseSysCache(atup);
 
    /*
     * If it's a multirange, step down to the range type, as is done by
     * multirange_typanalyze().
     */
    if (type_is_multirange(*atttypid))
        *atttypid = get_multirange_range(*atttypid);
 
    /* finds the right operators even if atttypid is a domain */
    typcache = lookup_type_cache(*atttypid, TYPECACHE_LT_OPR | TYPECACHE_EQ_OPR);
    *atttyptype = typcache->typtype;
    *eq_opr = typcache->eq_opr;
    *lt_opr = typcache->lt_opr;
 
    /*
     * Special case: collation for tsvector is DEFAULT_COLLATION_OID. See
     * compute_tsvector_stats().
     */
    if (*atttypid == TSVECTOROID)
        *atttypcoll = DEFAULT_COLLATION_OID;
 
    relation_close(rel, NoLock);
}
 
/*
 * Derive element type information from the attribute type.  This information
 * is needed when the given type is one that contains elements of other types.
 *
 * The atttypid and atttyptype should be derived from a previous call to
 * statatt_get_type().
 */
bool
statatt_get_elem_type(Oid atttypid, char atttyptype,
                      Oid *elemtypid, Oid *elem_eq_opr)
{
    TypeCacheEntry *elemtypcache;
 
    if (atttypid == TSVECTOROID)
    {
        /*
         * Special case: element type for tsvector is text. See
         * compute_tsvector_stats().
         */
        *elemtypid = TEXTOID;
    }
    else
    {
        /* find underlying element type through any domain */
        *elemtypid = get_base_element_type(atttypid);
    }
 
    if (!OidIsValid(*elemtypid))
        return false;
 
    /* finds the right operator even if elemtypid is a domain */
    elemtypcache = lookup_type_cache(*elemtypid, TYPECACHE_EQ_OPR);
    if (!OidIsValid(elemtypcache->eq_opr))
        return false;
 
    *elem_eq_opr = elemtypcache->eq_opr;
 
    return true;
}
 
/*
 * Build an array with element type typid from a text datum, used as
 * value of an attribute in a tuple to-be-inserted into pg_statistic.
 *
 * The typid and typmod should be derived from a previous call to
 * statatt_get_type().
 *
 * If an error is encountered, capture it and throw a WARNING, with "ok" set
 * to false.  If the resulting array contains NULLs, raise a WARNING and
 * set "ok" to false.  When the operation succeeds, set "ok" to true.
 */
Datum
statatt_build_stavalues(const char *staname, FmgrInfo *array_in, Datum d, Oid typid,
                        int32 typmod, bool *ok)
{
    char       *s;
    Datum       result;
    ErrorSaveContext escontext = {T_ErrorSaveContext};
 
    escontext.details_wanted = true;
 
    s = TextDatumGetCString(d);
 
    if (!InputFunctionCallSafe(array_in, s, typid, typmod,
                               (Node *) &escontext, &result))
    {
        pfree(s);
        escontext.error_data->elevel = WARNING;
        ThrowErrorData(escontext.error_data);
        *ok = false;
        return (Datum) 0;
    }
 
    pfree(s);
 
    if (ARR_NDIM(DatumGetArrayTypeP(result)) != 1)
    {
        ereport(WARNING,
                (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                 errmsg("\"%s\" must be a one-dimensional array", staname)));
        *ok = false;
        return (Datum) 0;
    }
 
    if (array_contains_nulls(DatumGetArrayTypeP(result)))
    {
        ereport(WARNING,
                (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                 errmsg("\"%s\" array must not contain null values", staname)));
        *ok = false;
        return (Datum) 0;
    }
 
    *ok = true;
 
    return result;
}
 
/*
 * Find and update the slot of a stakind, or use the first empty slot.
 *
 * Core statistics types expect the stakind value to be one of the
 * STATISTIC_KIND_* constants defined in pg_statistic.h, but types defined
 * by extensions are not restricted to those values.
 *
 * In the case of core statistics, the required staop is determined by the
 * stakind given and will either be a hardcoded oid, or the eq/lt operator
 * derived from statatt_get_type().  Likewise, types defined by extensions
 * have no such restriction.
 *
 * The stacoll value should be either the atttypcoll derived from
 * statatt_get_type(), or a hardcoded value required by that particular
 * stakind.
 *
 * The value/null pairs for stanumbers and stavalues should be calculated
 * based on the stakind, using statatt_build_stavalues() or constructed arrays.
 */
void
statatt_set_slot(Datum *values, bool *nulls, bool *replaces,
                 int16 stakind, Oid staop, Oid stacoll,
                 Datum stanumbers, bool stanumbers_isnull,
                 Datum stavalues, bool stavalues_isnull)
{
    int         slotidx;
    int         first_empty = -1;
    AttrNumber  stakind_attnum;
    AttrNumber  staop_attnum;
    AttrNumber  stacoll_attnum;
 
    /* find existing slot with given stakind */
    for (slotidx = 0; slotidx < STATISTIC_NUM_SLOTS; slotidx++)
    {
        stakind_attnum = Anum_pg_statistic_stakind1 - 1 + slotidx;
 
        if (first_empty < 0 &&
            DatumGetInt16(values[stakind_attnum]) == 0)
            first_empty = slotidx;
        if (DatumGetInt16(values[stakind_attnum]) == stakind)
            break;
    }
 
    if (slotidx >= STATISTIC_NUM_SLOTS && first_empty >= 0)
        slotidx = first_empty;
 
    if (slotidx >= STATISTIC_NUM_SLOTS)
        ereport(ERROR,
                (errmsg("maximum number of statistics slots exceeded: %d",
                        slotidx + 1)));
 
    stakind_attnum = Anum_pg_statistic_stakind1 - 1 + slotidx;
    staop_attnum = Anum_pg_statistic_staop1 - 1 + slotidx;
    stacoll_attnum = Anum_pg_statistic_stacoll1 - 1 + slotidx;
 
    if (DatumGetInt16(values[stakind_attnum]) != stakind)
    {
        values[stakind_attnum] = Int16GetDatum(stakind);
        replaces[stakind_attnum] = true;
    }
    if (DatumGetObjectId(values[staop_attnum]) != staop)
    {
        values[staop_attnum] = ObjectIdGetDatum(staop);
        replaces[staop_attnum] = true;
    }
    if (DatumGetObjectId(values[stacoll_attnum]) != stacoll)
    {
        values[stacoll_attnum] = ObjectIdGetDatum(stacoll);
        replaces[stacoll_attnum] = true;
    }
    if (!stanumbers_isnull)
    {
        values[Anum_pg_statistic_stanumbers1 - 1 + slotidx] = stanumbers;
        nulls[Anum_pg_statistic_stanumbers1 - 1 + slotidx] = false;
        replaces[Anum_pg_statistic_stanumbers1 - 1 + slotidx] = true;
    }
    if (!stavalues_isnull)
    {
        values[Anum_pg_statistic_stavalues1 - 1 + slotidx] = stavalues;
        nulls[Anum_pg_statistic_stavalues1 - 1 + slotidx] = false;
        replaces[Anum_pg_statistic_stavalues1 - 1 + slotidx] = true;
    }
}
 
/*
 * Initialize values and nulls for a new pg_statistic tuple.
 *
 * The caller is responsible for allocating the arrays where the results are
 * stored, which should be of size Natts_pg_statistic.
 *
 * When using this routine for a tuple inserted into pg_statistic, reloid,
 * attnum and inherited flags should all be set.
 *
 * When using this routine for a tuple that is an element of a stxdexpr
 * array inserted into pg_statistic_ext_data, reloid, attnum and inherited
 * should be respectively set to InvalidOid, InvalidAttrNumber and false.
 */
void
statatt_init_empty_tuple(Oid reloid, int16 attnum, bool inherited,
                         Datum *values, bool *nulls, bool *replaces)
{
    memset(nulls, true, sizeof(bool) * Natts_pg_statistic);
    memset(replaces, true, sizeof(bool) * Natts_pg_statistic);
 
    /* This must initialize non-NULL attributes */
    values[Anum_pg_statistic_starelid - 1] = ObjectIdGetDatum(reloid);
    nulls[Anum_pg_statistic_starelid - 1] = false;
    values[Anum_pg_statistic_staattnum - 1] = Int16GetDatum(attnum);
    nulls[Anum_pg_statistic_staattnum - 1] = false;
    values[Anum_pg_statistic_stainherit - 1] = BoolGetDatum(inherited);
    nulls[Anum_pg_statistic_stainherit - 1] = false;
 
    values[Anum_pg_statistic_stanullfrac - 1] = DEFAULT_STATATT_NULL_FRAC;
    nulls[Anum_pg_statistic_stanullfrac - 1] = false;
    values[Anum_pg_statistic_stawidth - 1] = DEFAULT_STATATT_AVG_WIDTH;
    nulls[Anum_pg_statistic_stawidth - 1] = false;
    values[Anum_pg_statistic_stadistinct - 1] = DEFAULT_STATATT_N_DISTINCT;
    nulls[Anum_pg_statistic_stadistinct - 1] = false;
 
    /* initialize stakind, staop, and stacoll slots */
    for (int slotnum = 0; slotnum < STATISTIC_NUM_SLOTS; slotnum++)
    {
        values[Anum_pg_statistic_stakind1 + slotnum - 1] = (Datum) 0;
        nulls[Anum_pg_statistic_stakind1 + slotnum - 1] = false;
        values[Anum_pg_statistic_staop1 + slotnum - 1] = ObjectIdGetDatum(InvalidOid);
        nulls[Anum_pg_statistic_staop1 + slotnum - 1] = false;
        values[Anum_pg_statistic_stacoll1 + slotnum - 1] = ObjectIdGetDatum(InvalidOid);
        nulls[Anum_pg_statistic_stacoll1 + slotnum - 1] = false;
    }
}
 
/*
 * Check that an imported bounds histogram (STATISTIC_KIND_BOUNDS_HISTOGRAM)
 * is shaped the same way ANALYZE builds it in compute_range_stats().
 *
 * For both range-typed and multirange-typed columns the histogram is an array
 * of ranges, so we take the range type from the array's element type.
 */
bool
statatt_check_bounds_histogram(Datum arrayval)
{
    ArrayType  *arr = DatumGetArrayTypeP(arrayval);
    Oid         rngtypid = ARR_ELEMTYPE(arr);
    TypeCacheEntry *typcache;
    int16       elmlen;
    bool        elmbyval;
    char        elmalign;
    Datum      *elems;
    bool       *nulls;
    int         nelems;
    RangeBound  prev_lower = {0};
    RangeBound  prev_upper = {0};
 
    typcache = lookup_type_cache(rngtypid, TYPECACHE_RANGE_INFO);
 
    /*
     * The element type should always be a range type here.  This is
     * defensive. If it isn't, the bounds histogram is never consulted by the
     * range estimator, and there is nothing to verify.
     */
    if (typcache->rngelemtype == NULL)
        return true;
 
    get_typlenbyvalalign(rngtypid, &elmlen, &elmbyval, &elmalign);
    deconstruct_array(arr, rngtypid, elmlen, elmbyval, elmalign,
                      &elems, &nulls, &nelems);
 
    for (int i = 0; i < nelems; i++)
    {
        RangeBound  lower,
                    upper;
        bool        empty;
 
        /*
         * NULL elements are already rejected by statatt_build_stavalues() and
         * array_in_safe().
         */
        range_deserialize(typcache, DatumGetRangeTypeP(elems[i]),
                          &lower, &upper, &empty);
 
        if (empty)
        {
            ereport(WARNING,
                    (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                     errmsg("\"%s\" must not contain empty ranges",
                            "range_bounds_histogram")));
            return false;
        }
 
        if (i > 0 &&
            (range_cmp_bounds(typcache, &lower, &prev_lower) < 0 ||
             range_cmp_bounds(typcache, &upper, &prev_upper) < 0))
        {
            ereport(WARNING,
                    (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                     errmsg("\"%s\" must have its lower and upper bounds sorted in ascending order",
                            "range_bounds_histogram")));
            return false;
        }
 
        prev_lower = lower;
        prev_upper = upper;
    }
 
    return true;
}