attribute_stats.c

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/*-------------------------------------------------------------------------
 * attribute_stats.c
 *
 *    PostgreSQL relation attribute statistics manipulation.
 *
 * Code supporting the direct import of relation attribute statistics, similar
 * to what is done by the ANALYZE command.
 *
 * Portions Copyright (c) 1996-2026, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * IDENTIFICATION
 *       src/backend/statistics/attribute_stats.c
 *
 *-------------------------------------------------------------------------
 */
 
#include "postgres.h"
 
#include "access/heapam.h"
#include "catalog/indexing.h"
#include "catalog/namespace.h"
#include "catalog/pg_operator.h"
#include "nodes/makefuncs.h"
#include "statistics/statistics.h"
#include "statistics/stat_utils.h"
#include "utils/array.h"
#include "utils/builtins.h"
#include "utils/fmgroids.h"
#include "utils/lsyscache.h"
#include "utils/syscache.h"
 
/*
 * Positional argument numbers, names, and types for
 * attribute_statistics_update() and pg_restore_attribute_stats().
 */
 
enum attribute_stats_argnum
{
    ATTRELSCHEMA_ARG = 0,
    ATTRELNAME_ARG,
    ATTNAME_ARG,
    ATTNUM_ARG,
    INHERITED_ARG,
    NULL_FRAC_ARG,
    AVG_WIDTH_ARG,
    N_DISTINCT_ARG,
    MOST_COMMON_VALS_ARG,
    MOST_COMMON_FREQS_ARG,
    HISTOGRAM_BOUNDS_ARG,
    CORRELATION_ARG,
    MOST_COMMON_ELEMS_ARG,
    MOST_COMMON_ELEM_FREQS_ARG,
    ELEM_COUNT_HISTOGRAM_ARG,
    RANGE_LENGTH_HISTOGRAM_ARG,
    RANGE_EMPTY_FRAC_ARG,
    RANGE_BOUNDS_HISTOGRAM_ARG,
    NUM_ATTRIBUTE_STATS_ARGS
};
 
static struct StatsArgInfo attarginfo[] =
{
    [ATTRELSCHEMA_ARG] = {"schemaname", TEXTOID},
    [ATTRELNAME_ARG] = {"relname", TEXTOID},
    [ATTNAME_ARG] = {"attname", TEXTOID},
    [ATTNUM_ARG] = {"attnum", INT2OID},
    [INHERITED_ARG] = {"inherited", BOOLOID},
    [NULL_FRAC_ARG] = {"null_frac", FLOAT4OID},
    [AVG_WIDTH_ARG] = {"avg_width", INT4OID},
    [N_DISTINCT_ARG] = {"n_distinct", FLOAT4OID},
    [MOST_COMMON_VALS_ARG] = {"most_common_vals", TEXTOID},
    [MOST_COMMON_FREQS_ARG] = {"most_common_freqs", FLOAT4ARRAYOID},
    [HISTOGRAM_BOUNDS_ARG] = {"histogram_bounds", TEXTOID},
    [CORRELATION_ARG] = {"correlation", FLOAT4OID},
    [MOST_COMMON_ELEMS_ARG] = {"most_common_elems", TEXTOID},
    [MOST_COMMON_ELEM_FREQS_ARG] = {"most_common_elem_freqs", FLOAT4ARRAYOID},
    [ELEM_COUNT_HISTOGRAM_ARG] = {"elem_count_histogram", FLOAT4ARRAYOID},
    [RANGE_LENGTH_HISTOGRAM_ARG] = {"range_length_histogram", TEXTOID},
    [RANGE_EMPTY_FRAC_ARG] = {"range_empty_frac", FLOAT4OID},
    [RANGE_BOUNDS_HISTOGRAM_ARG] = {"range_bounds_histogram", TEXTOID},
    [NUM_ATTRIBUTE_STATS_ARGS] = {0}
};
 
/*
 * Positional argument numbers, names, and types for
 * pg_clear_attribute_stats().
 */
 
enum clear_attribute_stats_argnum
{
    C_ATTRELSCHEMA_ARG = 0,
    C_ATTRELNAME_ARG,
    C_ATTNAME_ARG,
    C_INHERITED_ARG,
    C_NUM_ATTRIBUTE_STATS_ARGS
};
 
static struct StatsArgInfo cleararginfo[] =
{
    [C_ATTRELSCHEMA_ARG] = {"relation", TEXTOID},
    [C_ATTRELNAME_ARG] = {"relation", TEXTOID},
    [C_ATTNAME_ARG] = {"attname", TEXTOID},
    [C_INHERITED_ARG] = {"inherited", BOOLOID},
    [C_NUM_ATTRIBUTE_STATS_ARGS] = {0}
};
 
static bool attribute_statistics_update(FunctionCallInfo fcinfo);
static void upsert_pg_statistic(Relation starel, HeapTuple oldtup,
                                const Datum *values, const bool *nulls, const bool *replaces);
static bool delete_pg_statistic(Oid reloid, AttrNumber attnum, bool stainherit);
 
/*
 * Insert or Update Attribute Statistics
 *
 * See pg_statistic.h for an explanation of how each statistic kind is
 * stored. Custom statistics kinds are not supported.
 *
 * Depending on the statistics kind, we need to derive information from the
 * attribute for which we're storing the stats. For instance, the MCVs are
 * stored as an anyarray, and the representation of the array needs to store
 * the correct element type, which must be derived from the attribute.
 *
 * Major errors, such as the table not existing, the attribute not existing,
 * or a permissions failure are always reported at ERROR. Other errors, such
 * as a conversion failure on one statistic kind, are reported as a WARNING
 * and other statistic kinds may still be updated.
 */
static bool
attribute_statistics_update(FunctionCallInfo fcinfo)
{
    char       *nspname;
    char       *relname;
    Oid         reloid;
    char       *attname;
    AttrNumber  attnum;
    bool        inherited;
    Oid         locked_table = InvalidOid;
 
    Relation    starel;
    HeapTuple   statup;
 
    Oid         atttypid = InvalidOid;
    int32       atttypmod;
    char        atttyptype;
    Oid         atttypcoll = InvalidOid;
    Oid         eq_opr = InvalidOid;
    Oid         lt_opr = InvalidOid;
 
    Oid         elemtypid = InvalidOid;
    Oid         elem_eq_opr = InvalidOid;
 
    FmgrInfo    array_in_fn;
 
    bool        do_mcv = !PG_ARGISNULL(MOST_COMMON_FREQS_ARG) &&
        !PG_ARGISNULL(MOST_COMMON_VALS_ARG);
    bool        do_histogram = !PG_ARGISNULL(HISTOGRAM_BOUNDS_ARG);
    bool        do_correlation = !PG_ARGISNULL(CORRELATION_ARG);
    bool        do_mcelem = !PG_ARGISNULL(MOST_COMMON_ELEMS_ARG) &&
        !PG_ARGISNULL(MOST_COMMON_ELEM_FREQS_ARG);
    bool        do_dechist = !PG_ARGISNULL(ELEM_COUNT_HISTOGRAM_ARG);
    bool        do_bounds_histogram = !PG_ARGISNULL(RANGE_BOUNDS_HISTOGRAM_ARG);
    bool        do_range_length_histogram = !PG_ARGISNULL(RANGE_LENGTH_HISTOGRAM_ARG) &&
        !PG_ARGISNULL(RANGE_EMPTY_FRAC_ARG);
 
    Datum       values[Natts_pg_statistic] = {0};
    bool        nulls[Natts_pg_statistic] = {0};
    bool        replaces[Natts_pg_statistic] = {0};
 
    bool        result = true;
 
    stats_check_required_arg(fcinfo, attarginfo, ATTRELSCHEMA_ARG);
    stats_check_required_arg(fcinfo, attarginfo, ATTRELNAME_ARG);
 
    nspname = TextDatumGetCString(PG_GETARG_DATUM(ATTRELSCHEMA_ARG));
    relname = TextDatumGetCString(PG_GETARG_DATUM(ATTRELNAME_ARG));
 
    if (RecoveryInProgress())
        ereport(ERROR,
                (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
                 errmsg("recovery is in progress"),
                 errhint("Statistics cannot be modified during recovery.")));
 
    /* lock before looking up attribute */
    reloid = RangeVarGetRelidExtended(makeRangeVar(nspname, relname, -1),
                                      ShareUpdateExclusiveLock, 0,
                                      RangeVarCallbackForStats, &locked_table);
 
    /* user can specify either attname or attnum, but not both */
    if (!PG_ARGISNULL(ATTNAME_ARG))
    {
        if (!PG_ARGISNULL(ATTNUM_ARG))
            ereport(ERROR,
                    (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                     errmsg("cannot specify both \"%s\" and \"%s\"", "attname", "attnum")));
        attname = TextDatumGetCString(PG_GETARG_DATUM(ATTNAME_ARG));
        attnum = get_attnum(reloid, attname);
        /* note that this test covers attisdropped cases too: */
        if (attnum == InvalidAttrNumber)
            ereport(ERROR,
                    (errcode(ERRCODE_UNDEFINED_COLUMN),
                     errmsg("column \"%s\" of relation \"%s\" does not exist",
                            attname, relname)));
    }
    else if (!PG_ARGISNULL(ATTNUM_ARG))
    {
        attnum = PG_GETARG_INT16(ATTNUM_ARG);
        attname = get_attname(reloid, attnum, true);
        /* annoyingly, get_attname doesn't check attisdropped */
        if (attname == NULL ||
            !SearchSysCacheExistsAttName(reloid, attname))
            ereport(ERROR,
                    (errcode(ERRCODE_UNDEFINED_COLUMN),
                     errmsg("column %d of relation \"%s\" does not exist",
                            attnum, relname)));
    }
    else
    {
        ereport(ERROR,
                (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                 errmsg("must specify either \"%s\" or \"%s\"", "attname", "attnum")));
        attname = NULL;         /* keep compiler quiet */
        attnum = 0;
    }
 
    if (attnum < 0)
        ereport(ERROR,
                (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                 errmsg("cannot modify statistics on system column \"%s\"",
                        attname)));
 
    stats_check_required_arg(fcinfo, attarginfo, INHERITED_ARG);
    inherited = PG_GETARG_BOOL(INHERITED_ARG);
 
    /*
     * Check argument sanity. If some arguments are unusable, emit a WARNING
     * and set the corresponding argument to NULL in fcinfo.
     */
 
    if (!stats_check_arg_array(fcinfo, attarginfo, MOST_COMMON_FREQS_ARG))
    {
        do_mcv = false;
        result = false;
    }
 
    if (!stats_check_arg_array(fcinfo, attarginfo, MOST_COMMON_ELEM_FREQS_ARG))
    {
        do_mcelem = false;
        result = false;
    }
    if (!stats_check_arg_array(fcinfo, attarginfo, ELEM_COUNT_HISTOGRAM_ARG))
    {
        do_dechist = false;
        result = false;
    }
 
    if (!stats_check_arg_pair(fcinfo, attarginfo,
                              MOST_COMMON_VALS_ARG, MOST_COMMON_FREQS_ARG))
    {
        do_mcv = false;
        result = false;
    }
 
    if (!stats_check_arg_pair(fcinfo, attarginfo,
                              MOST_COMMON_ELEMS_ARG,
                              MOST_COMMON_ELEM_FREQS_ARG))
    {
        do_mcelem = false;
        result = false;
    }
 
    if (!stats_check_arg_pair(fcinfo, attarginfo,
                              RANGE_LENGTH_HISTOGRAM_ARG,
                              RANGE_EMPTY_FRAC_ARG))
    {
        do_range_length_histogram = false;
        result = false;
    }
 
    /* derive information from attribute */
    statatt_get_type(reloid, attnum,
                     &atttypid, &atttypmod,
                     &atttyptype, &atttypcoll,
                     &eq_opr, &lt_opr);
 
    /* if needed, derive element type */
    if (do_mcelem || do_dechist)
    {
        if (!statatt_get_elem_type(atttypid, atttyptype,
                                   &elemtypid, &elem_eq_opr))
        {
            ereport(WARNING,
                    (errmsg("could not determine element type of column \"%s\"", attname),
                     errdetail("Cannot set %s or %s.",
                               "STATISTIC_KIND_MCELEM", "STATISTIC_KIND_DECHIST")));
            elemtypid = InvalidOid;
            elem_eq_opr = InvalidOid;
 
            do_mcelem = false;
            do_dechist = false;
            result = false;
        }
    }
 
    /* histogram and correlation require less-than operator */
    if ((do_histogram || do_correlation) && !OidIsValid(lt_opr))
    {
        ereport(WARNING,
                (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                 errmsg("could not determine less-than operator for column \"%s\"", attname),
                 errdetail("Cannot set %s or %s.",
                           "STATISTIC_KIND_HISTOGRAM", "STATISTIC_KIND_CORRELATION")));
 
        do_histogram = false;
        do_correlation = false;
        result = false;
    }
 
    /* only range types can have range stats */
    if ((do_range_length_histogram || do_bounds_histogram) &&
        !(atttyptype == TYPTYPE_RANGE || atttyptype == TYPTYPE_MULTIRANGE))
    {
        ereport(WARNING,
                (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                 errmsg("column \"%s\" is not a range type", attname),
                 errdetail("Cannot set %s or %s.",
                           "STATISTIC_KIND_RANGE_LENGTH_HISTOGRAM", "STATISTIC_KIND_BOUNDS_HISTOGRAM")));
 
        do_bounds_histogram = false;
        do_range_length_histogram = false;
        result = false;
    }
 
    fmgr_info(F_ARRAY_IN, &array_in_fn);
 
    starel = table_open(StatisticRelationId, RowExclusiveLock);
 
    statup = SearchSysCache3(STATRELATTINH, ObjectIdGetDatum(reloid), Int16GetDatum(attnum), BoolGetDatum(inherited));
 
    /* initialize from existing tuple if exists */
    if (HeapTupleIsValid(statup))
        heap_deform_tuple(statup, RelationGetDescr(starel), values, nulls);
    else
        statatt_init_empty_tuple(reloid, attnum, inherited, values, nulls,
                                 replaces);
 
    /* if specified, set to argument values */
    if (!PG_ARGISNULL(NULL_FRAC_ARG))
    {
        values[Anum_pg_statistic_stanullfrac - 1] = PG_GETARG_DATUM(NULL_FRAC_ARG);
        replaces[Anum_pg_statistic_stanullfrac - 1] = true;
    }
    if (!PG_ARGISNULL(AVG_WIDTH_ARG))
    {
        values[Anum_pg_statistic_stawidth - 1] = PG_GETARG_DATUM(AVG_WIDTH_ARG);
        replaces[Anum_pg_statistic_stawidth - 1] = true;
    }
    if (!PG_ARGISNULL(N_DISTINCT_ARG))
    {
        values[Anum_pg_statistic_stadistinct - 1] = PG_GETARG_DATUM(N_DISTINCT_ARG);
        replaces[Anum_pg_statistic_stadistinct - 1] = true;
    }
 
    /* STATISTIC_KIND_MCV */
    if (do_mcv)
    {
        bool        converted;
        Datum       stanumbers = PG_GETARG_DATUM(MOST_COMMON_FREQS_ARG);
        Datum       stavalues = statatt_build_stavalues("most_common_vals",
                                                        &array_in_fn,
                                                        PG_GETARG_DATUM(MOST_COMMON_VALS_ARG),
                                                        atttypid, atttypmod,
                                                        &converted);
 
        if (converted)
        {
            ArrayType  *vals_arr = DatumGetArrayTypeP(stavalues);
            ArrayType  *nums_arr = DatumGetArrayTypeP(stanumbers);
            int         nvals = ARR_DIMS(vals_arr)[0];
            int         nnums = ARR_DIMS(nums_arr)[0];
 
            if (nvals != nnums)
            {
                ereport(WARNING,
                        (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
                         errmsg("could not parse \"%s\": incorrect number of elements (same as \"%s\" required)",
                                "most_common_vals",
                                "most_common_freqs")));
                result = false;
            }
            else
            {
                statatt_set_slot(values, nulls, replaces,
                                 STATISTIC_KIND_MCV,
                                 eq_opr, atttypcoll,
                                 stanumbers, false, stavalues, false);
            }
        }
        else
            result = false;
    }
 
    /* STATISTIC_KIND_HISTOGRAM */
    if (do_histogram)
    {
        Datum       stavalues;
        bool        converted = false;
 
        stavalues = statatt_build_stavalues("histogram_bounds",
                                            &array_in_fn,
                                            PG_GETARG_DATUM(HISTOGRAM_BOUNDS_ARG),
                                            atttypid, atttypmod,
                                            &converted);
 
        if (converted)
        {
            statatt_set_slot(values, nulls, replaces,
                             STATISTIC_KIND_HISTOGRAM,
                             lt_opr, atttypcoll,
                             0, true, stavalues, false);
        }
        else
            result = false;
    }
 
    /* STATISTIC_KIND_CORRELATION */
    if (do_correlation)
    {
        Datum       elems[] = {PG_GETARG_DATUM(CORRELATION_ARG)};
        ArrayType  *arry = construct_array_builtin(elems, 1, FLOAT4OID);
        Datum       stanumbers = PointerGetDatum(arry);
 
        statatt_set_slot(values, nulls, replaces,
                         STATISTIC_KIND_CORRELATION,
                         lt_opr, atttypcoll,
                         stanumbers, false, 0, true);
    }
 
    /* STATISTIC_KIND_MCELEM */
    if (do_mcelem)
    {
        Datum       stanumbers = PG_GETARG_DATUM(MOST_COMMON_ELEM_FREQS_ARG);
        bool        converted = false;
        Datum       stavalues;
 
        stavalues = statatt_build_stavalues("most_common_elems",
                                            &array_in_fn,
                                            PG_GETARG_DATUM(MOST_COMMON_ELEMS_ARG),
                                            elemtypid, atttypmod,
                                            &converted);
 
        if (converted)
        {
            statatt_set_slot(values, nulls, replaces,
                             STATISTIC_KIND_MCELEM,
                             elem_eq_opr, atttypcoll,
                             stanumbers, false, stavalues, false);
        }
        else
            result = false;
    }
 
    /* STATISTIC_KIND_DECHIST */
    if (do_dechist)
    {
        Datum       stanumbers = PG_GETARG_DATUM(ELEM_COUNT_HISTOGRAM_ARG);
 
        statatt_set_slot(values, nulls, replaces,
                         STATISTIC_KIND_DECHIST,
                         elem_eq_opr, atttypcoll,
                         stanumbers, false, 0, true);
    }
 
    /*
     * 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. We duplicate this quirk for consistency.
     */
    if (do_bounds_histogram)
    {
        bool        converted = false;
        Datum       stavalues;
 
        stavalues = statatt_build_stavalues("range_bounds_histogram",
                                            &array_in_fn,
                                            PG_GETARG_DATUM(RANGE_BOUNDS_HISTOGRAM_ARG),
                                            atttypid, atttypmod,
                                            &converted);
 
        if (converted)
        {
            statatt_set_slot(values, nulls, replaces,
                             STATISTIC_KIND_BOUNDS_HISTOGRAM,
                             InvalidOid, InvalidOid,
                             0, true, stavalues, false);
        }
        else
            result = false;
    }
 
    /* STATISTIC_KIND_RANGE_LENGTH_HISTOGRAM */
    if (do_range_length_histogram)
    {
        /* The anyarray is always a float8[] for this stakind */
        Datum       elems[] = {PG_GETARG_DATUM(RANGE_EMPTY_FRAC_ARG)};
        ArrayType  *arry = construct_array_builtin(elems, 1, FLOAT4OID);
        Datum       stanumbers = PointerGetDatum(arry);
 
        bool        converted = false;
        Datum       stavalues;
 
        stavalues = statatt_build_stavalues("range_length_histogram",
                                            &array_in_fn,
                                            PG_GETARG_DATUM(RANGE_LENGTH_HISTOGRAM_ARG),
                                            FLOAT8OID, 0, &converted);
 
        if (converted)
        {
            statatt_set_slot(values, nulls, replaces,
                             STATISTIC_KIND_RANGE_LENGTH_HISTOGRAM,
                             Float8LessOperator, InvalidOid,
                             stanumbers, false, stavalues, false);
        }
        else
            result = false;
    }
 
    upsert_pg_statistic(starel, statup, values, nulls, replaces);
 
    if (HeapTupleIsValid(statup))
        ReleaseSysCache(statup);
    table_close(starel, RowExclusiveLock);
 
    return result;
}
 
/*
 * Upsert the pg_statistic record.
 */
static void
upsert_pg_statistic(Relation starel, HeapTuple oldtup,
                    const Datum *values, const bool *nulls, const bool *replaces)
{
    HeapTuple   newtup;
 
    if (HeapTupleIsValid(oldtup))
    {
        newtup = heap_modify_tuple(oldtup, RelationGetDescr(starel),
                                   values, nulls, replaces);
        CatalogTupleUpdate(starel, &newtup->t_self, newtup);
    }
    else
    {
        newtup = heap_form_tuple(RelationGetDescr(starel), values, nulls);
        CatalogTupleInsert(starel, newtup);
    }
 
    heap_freetuple(newtup);
 
    CommandCounterIncrement();
}
 
/*
 * Delete pg_statistic record.
 */
static bool
delete_pg_statistic(Oid reloid, AttrNumber attnum, bool stainherit)
{
    Relation    sd = table_open(StatisticRelationId, RowExclusiveLock);
    HeapTuple   oldtup;
    bool        result = false;
 
    /* Is there already a pg_statistic tuple for this attribute? */
    oldtup = SearchSysCache3(STATRELATTINH,
                             ObjectIdGetDatum(reloid),
                             Int16GetDatum(attnum),
                             BoolGetDatum(stainherit));
 
    if (HeapTupleIsValid(oldtup))
    {
        CatalogTupleDelete(sd, &oldtup->t_self);
        ReleaseSysCache(oldtup);
        result = true;
    }
 
    table_close(sd, RowExclusiveLock);
 
    CommandCounterIncrement();
 
    return result;
}
 
/*
 * Delete statistics for the given attribute.
 */
Datum
pg_clear_attribute_stats(PG_FUNCTION_ARGS)
{
    char       *nspname;
    char       *relname;
    Oid         reloid;
    char       *attname;
    AttrNumber  attnum;
    bool        inherited;
    Oid         locked_table = InvalidOid;
 
    stats_check_required_arg(fcinfo, cleararginfo, C_ATTRELSCHEMA_ARG);
    stats_check_required_arg(fcinfo, cleararginfo, C_ATTRELNAME_ARG);
    stats_check_required_arg(fcinfo, cleararginfo, C_ATTNAME_ARG);
    stats_check_required_arg(fcinfo, cleararginfo, C_INHERITED_ARG);
 
    nspname = TextDatumGetCString(PG_GETARG_DATUM(C_ATTRELSCHEMA_ARG));
    relname = TextDatumGetCString(PG_GETARG_DATUM(C_ATTRELNAME_ARG));
 
    if (RecoveryInProgress())
        ereport(ERROR,
                (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
                 errmsg("recovery is in progress"),
                 errhint("Statistics cannot be modified during recovery.")));
 
    reloid = RangeVarGetRelidExtended(makeRangeVar(nspname, relname, -1),
                                      ShareUpdateExclusiveLock, 0,
                                      RangeVarCallbackForStats, &locked_table);
 
    attname = TextDatumGetCString(PG_GETARG_DATUM(C_ATTNAME_ARG));
    attnum = get_attnum(reloid, attname);
 
    if (attnum < 0)
        ereport(ERROR,
                (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
                 errmsg("cannot clear statistics on system column \"%s\"",
                        attname)));
 
    if (attnum == InvalidAttrNumber)
        ereport(ERROR,
                (errcode(ERRCODE_UNDEFINED_COLUMN),
                 errmsg("column \"%s\" of relation \"%s\" does not exist",
                        attname, get_rel_name(reloid))));
 
    inherited = PG_GETARG_BOOL(C_INHERITED_ARG);
 
    delete_pg_statistic(reloid, attnum, inherited);
    PG_RETURN_VOID();
}
 
/*
 * Import statistics for a given relation attribute.
 *
 * Inserts or replaces a row in pg_statistic for the given relation and
 * attribute name or number. It takes input parameters that correspond to
 * columns in the view pg_stats.
 *
 * Parameters are given in a pseudo named-attribute style: they must be
 * pairs of parameter names (as text) and values (of appropriate types).
 * We do that, rather than using regular named-parameter notation, so
 * that we can add or change parameters without fear of breaking
 * carelessly-written calls.
 *
 * Parameters null_frac, avg_width, and n_distinct all correspond to NOT NULL
 * columns in pg_statistic. The remaining parameters all belong to a specific
 * stakind. Some stakinds require multiple parameters, which must be specified
 * together (or neither specified).
 *
 * Parameters are only superficially validated. Omitting a parameter or
 * passing NULL leaves the statistic unchanged.
 *
 * Parameters corresponding to ANYARRAY columns are instead passed in as text
 * values, which is a valid input string for an array of the type or element
 * type of the attribute. Any error generated by the array_in() function will
 * in turn fail the function.
 */
Datum
pg_restore_attribute_stats(PG_FUNCTION_ARGS)
{
    LOCAL_FCINFO(positional_fcinfo, NUM_ATTRIBUTE_STATS_ARGS);
    bool        result = true;
 
    InitFunctionCallInfoData(*positional_fcinfo, NULL, NUM_ATTRIBUTE_STATS_ARGS,
                             InvalidOid, NULL, NULL);
 
    if (!stats_fill_fcinfo_from_arg_pairs(fcinfo, positional_fcinfo,
                                          attarginfo))
        result = false;
 
    if (!attribute_statistics_update(positional_fcinfo))
        result = false;
 
    PG_RETURN_BOOL(result);
}