array_selfuncs.c File Reference

#include "postgres.h"
#include <math.h>
#include "access/htup_details.h"
#include "catalog/pg_operator.h"
#include "catalog/pg_statistic.h"
#include "utils/array.h"
#include "utils/fmgrprotos.h"
#include "utils/lsyscache.h"
#include "utils/selfuncs.h"
#include "utils/typcache.h"

Include dependency graph for array_selfuncs.c:

Go to the source code of this file.

Macros
#define	DEFAULT_CONTAIN_SEL   0.005
#define	DEFAULT_OVERLAP_SEL   0.01
#define	DEFAULT_SEL(operator)
#define	EFFORT   100

Functions
static Selectivity	calc_arraycontsel (VariableStatData *vardata, Datum constval, Oid elemtype, Oid operator)
static Selectivity	mcelem_array_selec (const ArrayType *array, TypeCacheEntry *typentry, const Datum *mcelem, int nmcelem, const float4 *numbers, int nnumbers, const float4 *hist, int nhist, Oid operator)
static Selectivity	mcelem_array_contain_overlap_selec (const Datum *mcelem, int nmcelem, const float4 *numbers, int nnumbers, const Datum *array_data, int nitems, Oid operator, TypeCacheEntry *typentry)
static Selectivity	mcelem_array_contained_selec (const Datum *mcelem, int nmcelem, const float4 *numbers, int nnumbers, const Datum *array_data, int nitems, const float4 *hist, int nhist, Oid operator, TypeCacheEntry *typentry)
static float *	calc_hist (const float4 *hist, int nhist, int n)
static float *	calc_distr (const float *p, int n, int m, float rest)
static int	floor_log2 (uint32 n)
static bool	find_next_mcelem (const Datum *mcelem, int nmcelem, Datum value, int *index, TypeCacheEntry *typentry)
static int	element_compare (const void *key1, const void *key2, void *arg)
static int	float_compare_desc (const void *key1, const void *key2)
Selectivity	scalararraysel_containment (PlannerInfo *root, Node *leftop, Node *rightop, Oid elemtype, bool isEquality, bool useOr, int varRelid)
Datum	arraycontsel (PG_FUNCTION_ARGS)
Datum	arraycontjoinsel (PG_FUNCTION_ARGS)

Macro Definition Documentation

DEFAULT_CONTAIN_SEL

#define DEFAULT_CONTAIN_SEL   0.005

Definition at line 30 of file array_selfuncs.c.

DEFAULT_OVERLAP_SEL

#define DEFAULT_OVERLAP_SEL   0.01

Definition at line 33 of file array_selfuncs.c.

DEFAULT_SEL

#define DEFAULT_SEL

(

operator

)

Value:

    ((operator) == OID_ARRAY_OVERLAP_OP ? \
        DEFAULT_OVERLAP_SEL : DEFAULT_CONTAIN_SEL)

Definition at line 36 of file array_selfuncs.c.

EFFORT

#define EFFORT   100

Function Documentation

arraycontjoinsel()

Datum arraycontjoinsel

(

PG_FUNCTION_ARGS

)

Definition at line 321 of file array_selfuncs.c.

{
    /* For the moment this is just a stub */
    Oid         operator = PG_GETARG_OID(1);
 
    PG_RETURN_FLOAT8(DEFAULT_SEL(operator));
}

References DEFAULT_SEL, PG_GETARG_OID, and PG_RETURN_FLOAT8.

Referenced by _int_contained_joinsel(), _int_contains_joinsel(), and _int_overlap_joinsel().

arraycontsel()

Datum arraycontsel

(

PG_FUNCTION_ARGS

)

Definition at line 241 of file array_selfuncs.c.

{
    PlannerInfo *root = (PlannerInfo *) PG_GETARG_POINTER(0);
    Oid         operator = PG_GETARG_OID(1);
    List       *args = (List *) PG_GETARG_POINTER(2);
    int         varRelid = PG_GETARG_INT32(3);
    VariableStatData vardata;
    Node       *other;
    bool        varonleft;
    Selectivity selec;
    Oid         element_typeid;
 
    /*
     * If expression is not (variable op something) or (something op
     * variable), then punt and return a default estimate.
     */
    if (!get_restriction_variable(root, args, varRelid,
                                  &vardata, &other, &varonleft))
        PG_RETURN_FLOAT8(DEFAULT_SEL(operator));
 
    /*
     * Can't do anything useful if the something is not a constant, either.
     */
    if (!IsA(other, Const))
    {
        ReleaseVariableStats(vardata);
        PG_RETURN_FLOAT8(DEFAULT_SEL(operator));
    }
 
    /*
     * The "&&", "@>" and "<@" operators are strict, so we can cope with a
     * NULL constant right away.
     */
    if (((Const *) other)->constisnull)
    {
        ReleaseVariableStats(vardata);
        PG_RETURN_FLOAT8(0.0);
    }
 
    /*
     * If var is on the right, commute the operator, so that we can assume the
     * var is on the left in what follows.
     */
    if (!varonleft)
    {
        if (operator == OID_ARRAY_CONTAINS_OP)
            operator = OID_ARRAY_CONTAINED_OP;
        else if (operator == OID_ARRAY_CONTAINED_OP)
            operator = OID_ARRAY_CONTAINS_OP;
    }
 
    /*
     * OK, there's a Var and a Const we're dealing with here.  We need the
     * Const to be an array with same element type as column, else we can't do
     * anything useful.  (Such cases will likely fail at runtime, but here
     * we'd rather just return a default estimate.)
     */
    element_typeid = get_base_element_type(((Const *) other)->consttype);
    if (element_typeid != InvalidOid &&
        element_typeid == get_base_element_type(vardata.vartype))
    {
        selec = calc_arraycontsel(&vardata, ((Const *) other)->constvalue,
                                  element_typeid, operator);
    }
    else
    {
        selec = DEFAULT_SEL(operator);
    }
 
    ReleaseVariableStats(vardata);
 
    CLAMP_PROBABILITY(selec);
 
    PG_RETURN_FLOAT8((float8) selec);
}

References generate_unaccent_rules::args, calc_arraycontsel(), CLAMP_PROBABILITY, DEFAULT_SEL, get_base_element_type(), get_restriction_variable(), InvalidOid, IsA, PG_GETARG_INT32, PG_GETARG_OID, PG_GETARG_POINTER, PG_RETURN_FLOAT8, ReleaseVariableStats, root, and VariableStatData::vartype.

Referenced by _int_contained_sel(), _int_contains_sel(), and _int_overlap_sel().

calc_arraycontsel()

static Selectivity calc_arraycontsel ( VariableStatData *  vardata, Datum  constval, Oid  elemtype, Oid  operator  )

static

Definition at line 337 of file array_selfuncs.c.

{
    Selectivity selec;
    TypeCacheEntry *typentry;
    FmgrInfo   *cmpfunc;
    ArrayType  *array;
 
    /* Get element type's default comparison function */
    typentry = lookup_type_cache(elemtype, TYPECACHE_CMP_PROC_FINFO);
    if (!OidIsValid(typentry->cmp_proc_finfo.fn_oid))
        return DEFAULT_SEL(operator);
    cmpfunc = &typentry->cmp_proc_finfo;
 
    /*
     * The caller made sure the const is an array with same element type, so
     * get it now
     */
    array = DatumGetArrayTypeP(constval);
 
    if (HeapTupleIsValid(vardata->statsTuple) &&
        statistic_proc_security_check(vardata, cmpfunc->fn_oid))
    {
        Form_pg_statistic stats;
        AttStatsSlot sslot;
        AttStatsSlot hslot;
 
        stats = (Form_pg_statistic) GETSTRUCT(vardata->statsTuple);
 
        /* MCELEM will be an array of same type as column */
        if (get_attstatsslot(&sslot, vardata->statsTuple,
                             STATISTIC_KIND_MCELEM, InvalidOid,
                             ATTSTATSSLOT_VALUES | ATTSTATSSLOT_NUMBERS))
        {
            /*
             * For "array <@ const" case we also need histogram of distinct
             * element counts.
             */
            if (operator != OID_ARRAY_CONTAINED_OP ||
                !get_attstatsslot(&hslot, vardata->statsTuple,
                                  STATISTIC_KIND_DECHIST, InvalidOid,
                                  ATTSTATSSLOT_NUMBERS))
                memset(&hslot, 0, sizeof(hslot));
 
            /* Use the most-common-elements slot for the array Var. */
            selec = mcelem_array_selec(array, typentry,
                                       sslot.values, sslot.nvalues,
                                       sslot.numbers, sslot.nnumbers,
                                       hslot.numbers, hslot.nnumbers,
                                       operator);
 
            free_attstatsslot(&hslot);
            free_attstatsslot(&sslot);
        }
        else
        {
            /* No most-common-elements info, so do without */
            selec = mcelem_array_selec(array, typentry,
                                       NULL, 0, NULL, 0, NULL, 0,
                                       operator);
        }
 
        /*
         * MCE stats count only non-null rows, so adjust for null rows.
         */
        selec *= (1.0 - stats->stanullfrac);
    }
    else
    {
        /* No stats at all, so do without */
        selec = mcelem_array_selec(array, typentry,
                                   NULL, 0, NULL, 0, NULL, 0,
                                   operator);
        /* we assume no nulls here, so no stanullfrac correction */
    }
 
    /* If constant was toasted, release the copy we made */
    if (PointerGetDatum(array) != constval)
        pfree(array);
 
    return selec;
}

References ATTSTATSSLOT_NUMBERS, ATTSTATSSLOT_VALUES, TypeCacheEntry::cmp_proc_finfo, DatumGetArrayTypeP, DEFAULT_SEL, FmgrInfo::fn_oid, free_attstatsslot(), get_attstatsslot(), GETSTRUCT(), HeapTupleIsValid, InvalidOid, lookup_type_cache(), mcelem_array_selec(), AttStatsSlot::nnumbers, AttStatsSlot::numbers, AttStatsSlot::nvalues, OidIsValid, pfree(), PointerGetDatum(), statistic_proc_security_check(), VariableStatData::statsTuple, TYPECACHE_CMP_PROC_FINFO, and AttStatsSlot::values.

Referenced by arraycontsel().

calc_distr()

static float * calc_distr ( const float *  p, int  n, int  m, float  rest  )

static

Definition at line 1019 of file array_selfuncs.c.

{
    float      *row,
               *prev_row,
               *tmp;
    int         i,
                j;
 
    /*
     * Since we return only the last row of the matrix and need only the
     * current and previous row for calculations, allocate two rows.
     */
    row = (float *) palloc((m + 1) * sizeof(float));
    prev_row = (float *) palloc((m + 1) * sizeof(float));
 
    /* M[0,0] = 1 */
    row[0] = 1.0f;
    for (i = 1; i <= n; i++)
    {
        float       t = p[i - 1];
 
        /* Swap rows */
        tmp = row;
        row = prev_row;
        prev_row = tmp;
 
        /* Calculate next row */
        for (j = 0; j <= i && j <= m; j++)
        {
            float       val = 0.0f;
 
            if (j < i)
                val += prev_row[j] * (1.0f - t);
            if (j > 0)
                val += prev_row[j - 1] * t;
            row[j] = val;
        }
    }
 
    /*
     * The presence of many distinct rare (not in "p") elements materially
     * decreases selectivity.  Model their collective occurrence with the
     * Poisson distribution.
     */
    if (rest > DEFAULT_CONTAIN_SEL)
    {
        float       t;
 
        /* Swap rows */
        tmp = row;
        row = prev_row;
        prev_row = tmp;
 
        for (i = 0; i <= m; i++)
            row[i] = 0.0f;
 
        /* Value of Poisson distribution for 0 occurrences */
        t = exp(-rest);
 
        /*
         * Calculate convolution of previously computed distribution and the
         * Poisson distribution.
         */
        for (i = 0; i <= m; i++)
        {
            for (j = 0; j <= m - i; j++)
                row[j + i] += prev_row[j] * t;
 
            /* Get Poisson distribution value for (i + 1) occurrences */
            t *= rest / (float) (i + 1);
        }
    }
 
    pfree(prev_row);
    return row;
}

References DEFAULT_CONTAIN_SEL, i, j, palloc(), pfree(), and val.

Referenced by mcelem_array_contained_selec().

calc_hist()

static float * calc_hist ( const float4 *  hist, int  nhist, int  n  )

static

Definition at line 930 of file array_selfuncs.c.

{
    float      *hist_part;
    int         k,
                i = 0;
    float       prev_interval = 0,
                next_interval;
    float       frac;
 
    hist_part = (float *) palloc((n + 1) * sizeof(float));
 
    /*
     * frac is a probability contribution for each interval between histogram
     * values.  We have nhist - 1 intervals, so contribution of each one will
     * be 1 / (nhist - 1).
     */
    frac = 1.0f / ((float) (nhist - 1));
 
    for (k = 0; k <= n; k++)
    {
        int         count = 0;
 
        /*
         * Count the histogram boundaries equal to k.  (Although the histogram
         * should theoretically contain only exact integers, entries are
         * floats so there could be roundoff error in large values.  Treat any
         * fractional value as equal to the next larger k.)
         */
        while (i < nhist && hist[i] <= k)
        {
            count++;
            i++;
        }
 
        if (count > 0)
        {
            /* k is an exact bound for at least one histogram box. */
            float       val;
 
            /* Find length between current histogram value and the next one */
            if (i < nhist)
                next_interval = hist[i] - hist[i - 1];
            else
                next_interval = 0;
 
            /*
             * count - 1 histogram boxes contain k exclusively.  They
             * contribute a total of (count - 1) * frac probability.  Also
             * factor in the partial histogram boxes on either side.
             */
            val = (float) (count - 1);
            if (next_interval > 0)
                val += 0.5f / next_interval;
            if (prev_interval > 0)
                val += 0.5f / prev_interval;
            hist_part[k] = frac * val;
 
            prev_interval = next_interval;
        }
        else
        {
            /* k does not appear as an exact histogram bound. */
            if (prev_interval > 0)
                hist_part[k] = frac / prev_interval;
            else
                hist_part[k] = 0.0f;
        }
    }
 
    return hist_part;
}

References i, palloc(), and val.

Referenced by mcelem_array_contained_selec().

element_compare()

static int element_compare ( const void *  key1, const void *  key2, void *  arg  )

static

Definition at line 1174 of file array_selfuncs.c.

{
    Datum       d1 = *((const Datum *) key1);
    Datum       d2 = *((const Datum *) key2);
    TypeCacheEntry *typentry = (TypeCacheEntry *) arg;
    FmgrInfo   *cmpfunc = &typentry->cmp_proc_finfo;
    Datum       c;
 
    c = FunctionCall2Coll(cmpfunc, typentry->typcollation, d1, d2);
    return DatumGetInt32(c);
}

References arg, TypeCacheEntry::cmp_proc_finfo, DatumGetInt32(), FunctionCall2Coll(), and TypeCacheEntry::typcollation.

Referenced by find_next_mcelem(), mcelem_array_contain_overlap_selec(), mcelem_array_contained_selec(), and mcelem_array_selec().

find_next_mcelem()

static bool find_next_mcelem ( const Datum *  mcelem, int  nmcelem, Datum  value, int *  index, TypeCacheEntry *  typentry  )

static

Definition at line 1139 of file array_selfuncs.c.

{
    int         l = *index,
                r = nmcelem - 1,
                i,
                res;
 
    while (l <= r)
    {
        i = (l + r) / 2;
        res = element_compare(&mcelem[i], &value, typentry);
        if (res == 0)
        {
            *index = i;
            return true;
        }
        else if (res < 0)
            l = i + 1;
        else
            r = i - 1;
    }
    *index = l;
    return false;
}

References element_compare(), i, and value.

Referenced by mcelem_array_contain_overlap_selec().

float_compare_desc()

static int float_compare_desc ( const void *  key1, const void *  key2  )

static

Definition at line 1190 of file array_selfuncs.c.

{
    float       d1 = *((const float *) key1);
    float       d2 = *((const float *) key2);
 
    if (d1 > d2)
        return -1;
    else if (d1 < d2)
        return 1;
    else
        return 0;
}

Referenced by mcelem_array_contained_selec().

floor_log2()

static int floor_log2 ( uint32  n )

static

Definition at line 1098 of file array_selfuncs.c.

{
    int         logval = 0;
 
    if (n == 0)
        return -1;
    if (n >= (1 << 16))
    {
        n >>= 16;
        logval += 16;
    }
    if (n >= (1 << 8))
    {
        n >>= 8;
        logval += 8;
    }
    if (n >= (1 << 4))
    {
        n >>= 4;
        logval += 4;
    }
    if (n >= (1 << 2))
    {
        n >>= 2;
        logval += 2;
    }
    if (n >= (1 << 1))
    {
        logval += 1;
    }
    return logval;
}

Referenced by mcelem_array_contain_overlap_selec().

mcelem_array_contain_overlap_selec()

static Selectivity mcelem_array_contain_overlap_selec ( const Datum *  mcelem, int  nmcelem, const float4 *  numbers, int  nnumbers, const Datum *  array_data, int  nitems, Oid  operator, TypeCacheEntry *  typentry  )

static

Definition at line 521 of file array_selfuncs.c.

{
    Selectivity selec,
                elem_selec;
    int         mcelem_index,
                i;
    bool        use_bsearch;
    float4      minfreq;
 
    /*
     * There should be three more Numbers than Values, because the last three
     * cells should hold minimal and maximal frequency among the non-null
     * elements, and then the frequency of null elements.  Ignore the Numbers
     * if not right.
     */
    if (nnumbers != nmcelem + 3)
    {
        numbers = NULL;
        nnumbers = 0;
    }
 
    if (numbers)
    {
        /* Grab the minimal MCE frequency */
        minfreq = numbers[nmcelem];
    }
    else
    {
        /*
         * Without statistics, use DEFAULT_CONTAIN_SEL (the factor of 2 will
         * be removed again below).
         */
        minfreq = 2 * (float4) DEFAULT_CONTAIN_SEL;
    }
 
    /* Decide whether it is faster to use binary search or not. */
    if (nitems * floor_log2((uint32) nmcelem) < nmcelem + nitems)
        use_bsearch = true;
    else
        use_bsearch = false;
 
    if (operator == OID_ARRAY_CONTAINS_OP)
    {
        /*
         * Initial selectivity for "column @> const" query is 1.0, and it will
         * be decreased with each element of constant array.
         */
        selec = 1.0;
    }
    else
    {
        /*
         * Initial selectivity for "column && const" query is 0.0, and it will
         * be increased with each element of constant array.
         */
        selec = 0.0;
    }
 
    /* Scan mcelem and array in parallel. */
    mcelem_index = 0;
    for (i = 0; i < nitems; i++)
    {
        bool        match = false;
 
        /* Ignore any duplicates in the array data. */
        if (i > 0 &&
            element_compare(&array_data[i - 1], &array_data[i], typentry) == 0)
            continue;
 
        /* Find the smallest MCELEM >= this array item. */
        if (use_bsearch)
        {
            match = find_next_mcelem(mcelem, nmcelem, array_data[i],
                                     &mcelem_index, typentry);
        }
        else
        {
            while (mcelem_index < nmcelem)
            {
                int         cmp = element_compare(&mcelem[mcelem_index],
                                                  &array_data[i],
                                                  typentry);
 
                if (cmp < 0)
                    mcelem_index++;
                else
                {
                    if (cmp == 0)
                        match = true;   /* mcelem is found */
                    break;
                }
            }
        }
 
        if (match && numbers)
        {
            /* MCELEM matches the array item; use its frequency. */
            elem_selec = numbers[mcelem_index];
            mcelem_index++;
        }
        else
        {
            /*
             * The element is not in MCELEM.  Estimate its frequency as half
             * that of the least-frequent MCE.  (We know it cannot be more
             * than minfreq, and it could be a great deal less.  Half seems
             * like a good compromise.)  For probably-historical reasons,
             * clamp to not more than DEFAULT_CONTAIN_SEL.
             */
            elem_selec = Min(DEFAULT_CONTAIN_SEL, minfreq / 2);
        }
 
        /*
         * Update overall selectivity using the current element's selectivity
         * and an assumption of element occurrence independence.
         */
        if (operator == OID_ARRAY_CONTAINS_OP)
            selec *= elem_selec;
        else
            selec = selec + elem_selec - selec * elem_selec;
 
        /* Clamp intermediate results to stay sane despite roundoff error */
        CLAMP_PROBABILITY(selec);
    }
 
    return selec;
}

References CLAMP_PROBABILITY, cmp(), DEFAULT_CONTAIN_SEL, element_compare(), find_next_mcelem(), floor_log2(), i, Min, and nitems.

Referenced by mcelem_array_selec(), and scalararraysel_containment().

mcelem_array_contained_selec()

static Selectivity mcelem_array_contained_selec ( const Datum *  mcelem, int  nmcelem, const float4 *  numbers, int  nnumbers, const Datum *  array_data, int  nitems, const float4 *  hist, int  nhist, Oid  operator, TypeCacheEntry *  typentry  )

static

Definition at line 702 of file array_selfuncs.c.

{
    int         mcelem_index,
                i,
                unique_nitems = 0;
    float       selec,
                minfreq,
                nullelem_freq;
    float      *dist,
               *mcelem_dist,
               *hist_part;
    float       avg_count,
                mult,
                rest;
    float      *elem_selec;
 
    /*
     * There should be three more Numbers than Values in the MCELEM slot,
     * because the last three cells should hold minimal and maximal frequency
     * among the non-null elements, and then the frequency of null elements.
     * Punt if not right, because we can't do much without the element freqs.
     */
    if (numbers == NULL || nnumbers != nmcelem + 3)
        return DEFAULT_CONTAIN_SEL;
 
    /* Can't do much without a count histogram, either */
    if (hist == NULL || nhist < 3)
        return DEFAULT_CONTAIN_SEL;
 
    /*
     * Grab some of the summary statistics that compute_array_stats() stores:
     * lowest MCE frequency, frequency of null elements, and average distinct
     * element count.
     */
    minfreq = numbers[nmcelem];
    nullelem_freq = numbers[nmcelem + 2];
    avg_count = hist[nhist - 1];
 
    /*
     * "rest" will be the sum of the frequencies of all elements not
     * represented in MCELEM.  The average distinct element count is the sum
     * of the frequencies of *all* elements.  Begin with that; we will proceed
     * to subtract the MCELEM frequencies.
     */
    rest = avg_count;
 
    /*
     * mult is a multiplier representing estimate of probability that each
     * mcelem that is not present in constant doesn't occur.
     */
    mult = 1.0f;
 
    /*
     * elem_selec is array of estimated frequencies for elements in the
     * constant.
     */
    elem_selec = (float *) palloc(sizeof(float) * nitems);
 
    /* Scan mcelem and array in parallel. */
    mcelem_index = 0;
    for (i = 0; i < nitems; i++)
    {
        bool        match = false;
 
        /* Ignore any duplicates in the array data. */
        if (i > 0 &&
            element_compare(&array_data[i - 1], &array_data[i], typentry) == 0)
            continue;
 
        /*
         * Iterate over MCELEM until we find an entry greater than or equal to
         * this element of the constant.  Update "rest" and "mult" for mcelem
         * entries skipped over.
         */
        while (mcelem_index < nmcelem)
        {
            int         cmp = element_compare(&mcelem[mcelem_index],
                                              &array_data[i],
                                              typentry);
 
            if (cmp < 0)
            {
                mult *= (1.0f - numbers[mcelem_index]);
                rest -= numbers[mcelem_index];
                mcelem_index++;
            }
            else
            {
                if (cmp == 0)
                    match = true;   /* mcelem is found */
                break;
            }
        }
 
        if (match)
        {
            /* MCELEM matches the array item. */
            elem_selec[unique_nitems] = numbers[mcelem_index];
            /* "rest" is decremented for all mcelems, matched or not */
            rest -= numbers[mcelem_index];
            mcelem_index++;
        }
        else
        {
            /*
             * The element is not in MCELEM.  Estimate its frequency as half
             * that of the least-frequent MCE.  (We know it cannot be more
             * than minfreq, and it could be a great deal less.  Half seems
             * like a good compromise.)  For probably-historical reasons,
             * clamp to not more than DEFAULT_CONTAIN_SEL.
             */
            elem_selec[unique_nitems] = Min(DEFAULT_CONTAIN_SEL,
                                            minfreq / 2);
        }
 
        unique_nitems++;
    }
 
    /*
     * If we handled all constant elements without exhausting the MCELEM
     * array, finish walking it to complete calculation of "rest" and "mult".
     */
    while (mcelem_index < nmcelem)
    {
        mult *= (1.0f - numbers[mcelem_index]);
        rest -= numbers[mcelem_index];
        mcelem_index++;
    }
 
    /*
     * The presence of many distinct rare elements materially decreases
     * selectivity.  Use the Poisson distribution to estimate the probability
     * of a column value having zero occurrences of such elements.  See above
     * for the definition of "rest".
     */
    mult *= exp(-rest);
 
    /*----------
     * Using the distinct element count histogram requires
     *      O(unique_nitems * (nmcelem + unique_nitems))
     * operations.  Beyond a certain computational cost threshold, it's
     * reasonable to sacrifice accuracy for decreased planning time.  We limit
     * the number of operations to EFFORT * nmcelem; since nmcelem is limited
     * by the column's statistics target, the work done is user-controllable.
     *
     * If the number of operations would be too large, we can reduce it
     * without losing all accuracy by reducing unique_nitems and considering
     * only the most-common elements of the constant array.  To make the
     * results exactly match what we would have gotten with only those
     * elements to start with, we'd have to remove any discarded elements'
     * frequencies from "mult", but since this is only an approximation
     * anyway, we don't bother with that.  Therefore it's sufficient to qsort
     * elem_selec[] and take the largest elements.  (They will no longer match
     * up with the elements of array_data[], but we don't care.)
     *----------
     */
#define EFFORT 100
 
    if ((nmcelem + unique_nitems) > 0 &&
        unique_nitems > EFFORT * nmcelem / (nmcelem + unique_nitems))
    {
        /*
         * Use the quadratic formula to solve for largest allowable N.  We
         * have A = 1, B = nmcelem, C = - EFFORT * nmcelem.
         */
        double      b = (double) nmcelem;
        int         n;
 
        n = (int) ((sqrt(b * b + 4 * EFFORT * b) - b) / 2);
 
        /* Sort, then take just the first n elements */
        qsort(elem_selec, unique_nitems, sizeof(float),
              float_compare_desc);
        unique_nitems = n;
    }
 
    /*
     * Calculate probabilities of each distinct element count for both mcelems
     * and constant elements.  At this point, assume independent element
     * occurrence.
     */
    dist = calc_distr(elem_selec, unique_nitems, unique_nitems, 0.0f);
    mcelem_dist = calc_distr(numbers, nmcelem, unique_nitems, rest);
 
    /* ignore hist[nhist-1], which is the average not a histogram member */
    hist_part = calc_hist(hist, nhist - 1, unique_nitems);
 
    selec = 0.0f;
    for (i = 0; i <= unique_nitems; i++)
    {
        /*
         * mult * dist[i] / mcelem_dist[i] gives us probability of qual
         * matching from assumption of independent element occurrence with the
         * condition that distinct element count = i.
         */
        if (mcelem_dist[i] > 0)
            selec += hist_part[i] * mult * dist[i] / mcelem_dist[i];
    }
 
    pfree(dist);
    pfree(mcelem_dist);
    pfree(hist_part);
    pfree(elem_selec);
 
    /* Take into account occurrence of NULL element. */
    selec *= (1.0f - nullelem_freq);
 
    CLAMP_PROBABILITY(selec);
 
    return selec;
}

References b, calc_distr(), calc_hist(), CLAMP_PROBABILITY, cmp(), DEFAULT_CONTAIN_SEL, EFFORT, element_compare(), float_compare_desc(), i, Min, nitems, palloc(), pfree(), and qsort.

Referenced by mcelem_array_selec(), and scalararraysel_containment().

mcelem_array_selec()

static Selectivity mcelem_array_selec ( const ArrayType *  array, TypeCacheEntry *  typentry, const Datum *  mcelem, int  nmcelem, const float4 *  numbers, int  nnumbers, const float4 *  hist, int  nhist, Oid  operator  )

static

Definition at line 428 of file array_selfuncs.c.

{
    Selectivity selec;
    int         num_elems;
    Datum      *elem_values;
    bool       *elem_nulls;
    bool        null_present;
    int         nonnull_nitems;
    int         i;
 
    /*
     * Prepare constant array data for sorting.  Sorting lets us find unique
     * elements and efficiently merge with the MCELEM array.
     */
    deconstruct_array(array,
                      typentry->type_id,
                      typentry->typlen,
                      typentry->typbyval,
                      typentry->typalign,
                      &elem_values, &elem_nulls, &num_elems);
 
    /* Collapse out any null elements */
    nonnull_nitems = 0;
    null_present = false;
    for (i = 0; i < num_elems; i++)
    {
        if (elem_nulls[i])
            null_present = true;
        else
            elem_values[nonnull_nitems++] = elem_values[i];
    }
 
    /*
     * Query "column @> '{anything, null}'" matches nothing.  For the other
     * two operators, presence of a null in the constant can be ignored.
     */
    if (null_present && operator == OID_ARRAY_CONTAINS_OP)
    {
        pfree(elem_values);
        pfree(elem_nulls);
        return (Selectivity) 0.0;
    }
 
    /* Sort extracted elements using their default comparison function. */
    qsort_arg(elem_values, nonnull_nitems, sizeof(Datum),
              element_compare, typentry);
 
    /* Separate cases according to operator */
    if (operator == OID_ARRAY_CONTAINS_OP || operator == OID_ARRAY_OVERLAP_OP)
        selec = mcelem_array_contain_overlap_selec(mcelem, nmcelem,
                                                   numbers, nnumbers,
                                                   elem_values, nonnull_nitems,
                                                   operator, typentry);
    else if (operator == OID_ARRAY_CONTAINED_OP)
        selec = mcelem_array_contained_selec(mcelem, nmcelem,
                                             numbers, nnumbers,
                                             elem_values, nonnull_nitems,
                                             hist, nhist,
                                             operator, typentry);
    else
    {
        elog(ERROR, "arraycontsel called for unrecognized operator %u",
             operator);
        selec = 0.0;            /* keep compiler quiet */
    }
 
    pfree(elem_values);
    pfree(elem_nulls);
    return selec;
}

References deconstruct_array(), element_compare(), elog, ERROR, i, mcelem_array_contain_overlap_selec(), mcelem_array_contained_selec(), pfree(), qsort_arg(), TypeCacheEntry::typalign, TypeCacheEntry::typbyval, TypeCacheEntry::type_id, and TypeCacheEntry::typlen.

Referenced by calc_arraycontsel().

scalararraysel_containment()

Selectivity scalararraysel_containment	(	PlannerInfo *	root,
		Node *	leftop,
		Node *	rightop,
		Oid	elemtype,
		bool	isEquality,
		bool	useOr,
		int	varRelid
	)

Definition at line 81 of file array_selfuncs.c.

{
    Selectivity selec;
    VariableStatData vardata;
    Datum       constval;
    TypeCacheEntry *typentry;
    FmgrInfo   *cmpfunc;
 
    /*
     * rightop must be a variable, else punt.
     */
    examine_variable(root, rightop, varRelid, &vardata);
    if (!vardata.rel)
    {
        ReleaseVariableStats(vardata);
        return -1.0;
    }
 
    /*
     * leftop must be a constant, else punt.
     */
    if (!IsA(leftop, Const))
    {
        ReleaseVariableStats(vardata);
        return -1.0;
    }
    if (((Const *) leftop)->constisnull)
    {
        /* qual can't succeed if null on left */
        ReleaseVariableStats(vardata);
        return (Selectivity) 0.0;
    }
    constval = ((Const *) leftop)->constvalue;
 
    /* Get element type's default comparison function */
    typentry = lookup_type_cache(elemtype, TYPECACHE_CMP_PROC_FINFO);
    if (!OidIsValid(typentry->cmp_proc_finfo.fn_oid))
    {
        ReleaseVariableStats(vardata);
        return -1.0;
    }
    cmpfunc = &typentry->cmp_proc_finfo;
 
    /*
     * If the operator is <>, swap ANY/ALL, then invert the result later.
     */
    if (!isEquality)
        useOr = !useOr;
 
    /* Get array element stats for var, if available */
    if (HeapTupleIsValid(vardata.statsTuple) &&
        statistic_proc_security_check(&vardata, cmpfunc->fn_oid))
    {
        Form_pg_statistic stats;
        AttStatsSlot sslot;
        AttStatsSlot hslot;
 
        stats = (Form_pg_statistic) GETSTRUCT(vardata.statsTuple);
 
        /* MCELEM will be an array of same type as element */
        if (get_attstatsslot(&sslot, vardata.statsTuple,
                             STATISTIC_KIND_MCELEM, InvalidOid,
                             ATTSTATSSLOT_VALUES | ATTSTATSSLOT_NUMBERS))
        {
            /* For ALL case, also get histogram of distinct-element counts */
            if (useOr ||
                !get_attstatsslot(&hslot, vardata.statsTuple,
                                  STATISTIC_KIND_DECHIST, InvalidOid,
                                  ATTSTATSSLOT_NUMBERS))
                memset(&hslot, 0, sizeof(hslot));
 
            /*
             * For = ANY, estimate as var @> ARRAY[const].
             *
             * For = ALL, estimate as var <@ ARRAY[const].
             */
            if (useOr)
                selec = mcelem_array_contain_overlap_selec(sslot.values,
                                                           sslot.nvalues,
                                                           sslot.numbers,
                                                           sslot.nnumbers,
                                                           &constval, 1,
                                                           OID_ARRAY_CONTAINS_OP,
                                                           typentry);
            else
                selec = mcelem_array_contained_selec(sslot.values,
                                                     sslot.nvalues,
                                                     sslot.numbers,
                                                     sslot.nnumbers,
                                                     &constval, 1,
                                                     hslot.numbers,
                                                     hslot.nnumbers,
                                                     OID_ARRAY_CONTAINED_OP,
                                                     typentry);
 
            free_attstatsslot(&hslot);
            free_attstatsslot(&sslot);
        }
        else
        {
            /* No most-common-elements info, so do without */
            if (useOr)
                selec = mcelem_array_contain_overlap_selec(NULL, 0,
                                                           NULL, 0,
                                                           &constval, 1,
                                                           OID_ARRAY_CONTAINS_OP,
                                                           typentry);
            else
                selec = mcelem_array_contained_selec(NULL, 0,
                                                     NULL, 0,
                                                     &constval, 1,
                                                     NULL, 0,
                                                     OID_ARRAY_CONTAINED_OP,
                                                     typentry);
        }
 
        /*
         * MCE stats count only non-null rows, so adjust for null rows.
         */
        selec *= (1.0 - stats->stanullfrac);
    }
    else
    {
        /* No stats at all, so do without */
        if (useOr)
            selec = mcelem_array_contain_overlap_selec(NULL, 0,
                                                       NULL, 0,
                                                       &constval, 1,
                                                       OID_ARRAY_CONTAINS_OP,
                                                       typentry);
        else
            selec = mcelem_array_contained_selec(NULL, 0,
                                                 NULL, 0,
                                                 &constval, 1,
                                                 NULL, 0,
                                                 OID_ARRAY_CONTAINED_OP,
                                                 typentry);
        /* we assume no nulls here, so no stanullfrac correction */
    }
 
    ReleaseVariableStats(vardata);
 
    /*
     * If the operator is <>, invert the results.
     */
    if (!isEquality)
        selec = 1.0 - selec;
 
    CLAMP_PROBABILITY(selec);
 
    return selec;
}

References ATTSTATSSLOT_NUMBERS, ATTSTATSSLOT_VALUES, CLAMP_PROBABILITY, TypeCacheEntry::cmp_proc_finfo, examine_variable(), FmgrInfo::fn_oid, free_attstatsslot(), get_attstatsslot(), GETSTRUCT(), HeapTupleIsValid, InvalidOid, IsA, lookup_type_cache(), mcelem_array_contain_overlap_selec(), mcelem_array_contained_selec(), AttStatsSlot::nnumbers, AttStatsSlot::numbers, AttStatsSlot::nvalues, OidIsValid, VariableStatData::rel, ReleaseVariableStats, root, statistic_proc_security_check(), VariableStatData::statsTuple, TYPECACHE_CMP_PROC_FINFO, and AttStatsSlot::values.

Referenced by scalararraysel().