LCOV - code coverage report
Current view: top level - src/backend/utils/adt - array_selfuncs.c (source / functions) Hit Total Coverage
Test: PostgreSQL 17devel Lines: 260 319 81.5 %
Date: 2024-03-28 16:11:17 Functions: 12 13 92.3 %
Legend: Lines: hit not hit

          Line data    Source code
       1             : /*-------------------------------------------------------------------------
       2             :  *
       3             :  * array_selfuncs.c
       4             :  *    Functions for selectivity estimation of array operators
       5             :  *
       6             :  * Portions Copyright (c) 1996-2024, PostgreSQL Global Development Group
       7             :  * Portions Copyright (c) 1994, Regents of the University of California
       8             :  *
       9             :  *
      10             :  * IDENTIFICATION
      11             :  *    src/backend/utils/adt/array_selfuncs.c
      12             :  *
      13             :  *-------------------------------------------------------------------------
      14             :  */
      15             : #include "postgres.h"
      16             : 
      17             : #include <math.h>
      18             : 
      19             : #include "access/htup_details.h"
      20             : #include "catalog/pg_operator.h"
      21             : #include "catalog/pg_statistic.h"
      22             : #include "utils/array.h"
      23             : #include "utils/fmgrprotos.h"
      24             : #include "utils/lsyscache.h"
      25             : #include "utils/selfuncs.h"
      26             : #include "utils/typcache.h"
      27             : 
      28             : 
      29             : /* Default selectivity constant for "@>" and "<@" operators */
      30             : #define DEFAULT_CONTAIN_SEL 0.005
      31             : 
      32             : /* Default selectivity constant for "&&" operator */
      33             : #define DEFAULT_OVERLAP_SEL 0.01
      34             : 
      35             : /* Default selectivity for given operator */
      36             : #define DEFAULT_SEL(operator) \
      37             :     ((operator) == OID_ARRAY_OVERLAP_OP ? \
      38             :         DEFAULT_OVERLAP_SEL : DEFAULT_CONTAIN_SEL)
      39             : 
      40             : static Selectivity calc_arraycontsel(VariableStatData *vardata, Datum constval,
      41             :                                      Oid elemtype, Oid operator);
      42             : static Selectivity mcelem_array_selec(ArrayType *array,
      43             :                                       TypeCacheEntry *typentry,
      44             :                                       Datum *mcelem, int nmcelem,
      45             :                                       float4 *numbers, int nnumbers,
      46             :                                       float4 *hist, int nhist,
      47             :                                       Oid operator);
      48             : static Selectivity mcelem_array_contain_overlap_selec(Datum *mcelem, int nmcelem,
      49             :                                                       float4 *numbers, int nnumbers,
      50             :                                                       Datum *array_data, int nitems,
      51             :                                                       Oid operator, TypeCacheEntry *typentry);
      52             : static Selectivity mcelem_array_contained_selec(Datum *mcelem, int nmcelem,
      53             :                                                 float4 *numbers, int nnumbers,
      54             :                                                 Datum *array_data, int nitems,
      55             :                                                 float4 *hist, int nhist,
      56             :                                                 Oid operator, TypeCacheEntry *typentry);
      57             : static float *calc_hist(const float4 *hist, int nhist, int n);
      58             : static float *calc_distr(const float *p, int n, int m, float rest);
      59             : static int  floor_log2(uint32 n);
      60             : static bool find_next_mcelem(Datum *mcelem, int nmcelem, Datum value,
      61             :                              int *index, TypeCacheEntry *typentry);
      62             : static int  element_compare(const void *key1, const void *key2, void *arg);
      63             : static int  float_compare_desc(const void *key1, const void *key2);
      64             : 
      65             : 
      66             : /*
      67             :  * scalararraysel_containment
      68             :  *      Estimate selectivity of ScalarArrayOpExpr via array containment.
      69             :  *
      70             :  * If we have const =/<> ANY/ALL (array_var) then we can estimate the
      71             :  * selectivity as though this were an array containment operator,
      72             :  * array_var op ARRAY[const].
      73             :  *
      74             :  * scalararraysel() has already verified that the ScalarArrayOpExpr's operator
      75             :  * is the array element type's default equality or inequality operator, and
      76             :  * has aggressively simplified both inputs to constants.
      77             :  *
      78             :  * Returns selectivity (0..1), or -1 if we fail to estimate selectivity.
      79             :  */
      80             : Selectivity
      81       15580 : scalararraysel_containment(PlannerInfo *root,
      82             :                            Node *leftop, Node *rightop,
      83             :                            Oid elemtype, bool isEquality, bool useOr,
      84             :                            int varRelid)
      85             : {
      86             :     Selectivity selec;
      87             :     VariableStatData vardata;
      88             :     Datum       constval;
      89             :     TypeCacheEntry *typentry;
      90             :     FmgrInfo   *cmpfunc;
      91             : 
      92             :     /*
      93             :      * rightop must be a variable, else punt.
      94             :      */
      95       15580 :     examine_variable(root, rightop, varRelid, &vardata);
      96       15580 :     if (!vardata.rel)
      97             :     {
      98       15176 :         ReleaseVariableStats(vardata);
      99       15176 :         return -1.0;
     100             :     }
     101             : 
     102             :     /*
     103             :      * leftop must be a constant, else punt.
     104             :      */
     105         404 :     if (!IsA(leftop, Const))
     106             :     {
     107         286 :         ReleaseVariableStats(vardata);
     108         286 :         return -1.0;
     109             :     }
     110         118 :     if (((Const *) leftop)->constisnull)
     111             :     {
     112             :         /* qual can't succeed if null on left */
     113           0 :         ReleaseVariableStats(vardata);
     114           0 :         return (Selectivity) 0.0;
     115             :     }
     116         118 :     constval = ((Const *) leftop)->constvalue;
     117             : 
     118             :     /* Get element type's default comparison function */
     119         118 :     typentry = lookup_type_cache(elemtype, TYPECACHE_CMP_PROC_FINFO);
     120         118 :     if (!OidIsValid(typentry->cmp_proc_finfo.fn_oid))
     121             :     {
     122           0 :         ReleaseVariableStats(vardata);
     123           0 :         return -1.0;
     124             :     }
     125         118 :     cmpfunc = &typentry->cmp_proc_finfo;
     126             : 
     127             :     /*
     128             :      * If the operator is <>, swap ANY/ALL, then invert the result later.
     129             :      */
     130         118 :     if (!isEquality)
     131          86 :         useOr = !useOr;
     132             : 
     133             :     /* Get array element stats for var, if available */
     134         130 :     if (HeapTupleIsValid(vardata.statsTuple) &&
     135          12 :         statistic_proc_security_check(&vardata, cmpfunc->fn_oid))
     136          12 :     {
     137             :         Form_pg_statistic stats;
     138             :         AttStatsSlot sslot;
     139             :         AttStatsSlot hslot;
     140             : 
     141          12 :         stats = (Form_pg_statistic) GETSTRUCT(vardata.statsTuple);
     142             : 
     143             :         /* MCELEM will be an array of same type as element */
     144          12 :         if (get_attstatsslot(&sslot, vardata.statsTuple,
     145             :                              STATISTIC_KIND_MCELEM, InvalidOid,
     146             :                              ATTSTATSSLOT_VALUES | ATTSTATSSLOT_NUMBERS))
     147             :         {
     148             :             /* For ALL case, also get histogram of distinct-element counts */
     149          12 :             if (useOr ||
     150           0 :                 !get_attstatsslot(&hslot, vardata.statsTuple,
     151             :                                   STATISTIC_KIND_DECHIST, InvalidOid,
     152             :                                   ATTSTATSSLOT_NUMBERS))
     153          12 :                 memset(&hslot, 0, sizeof(hslot));
     154             : 
     155             :             /*
     156             :              * For = ANY, estimate as var @> ARRAY[const].
     157             :              *
     158             :              * For = ALL, estimate as var <@ ARRAY[const].
     159             :              */
     160          12 :             if (useOr)
     161          12 :                 selec = mcelem_array_contain_overlap_selec(sslot.values,
     162             :                                                            sslot.nvalues,
     163             :                                                            sslot.numbers,
     164             :                                                            sslot.nnumbers,
     165             :                                                            &constval, 1,
     166             :                                                            OID_ARRAY_CONTAINS_OP,
     167             :                                                            typentry);
     168             :             else
     169           0 :                 selec = mcelem_array_contained_selec(sslot.values,
     170             :                                                      sslot.nvalues,
     171             :                                                      sslot.numbers,
     172             :                                                      sslot.nnumbers,
     173             :                                                      &constval, 1,
     174             :                                                      hslot.numbers,
     175             :                                                      hslot.nnumbers,
     176             :                                                      OID_ARRAY_CONTAINED_OP,
     177             :                                                      typentry);
     178             : 
     179          12 :             free_attstatsslot(&hslot);
     180          12 :             free_attstatsslot(&sslot);
     181             :         }
     182             :         else
     183             :         {
     184             :             /* No most-common-elements info, so do without */
     185           0 :             if (useOr)
     186           0 :                 selec = mcelem_array_contain_overlap_selec(NULL, 0,
     187             :                                                            NULL, 0,
     188             :                                                            &constval, 1,
     189             :                                                            OID_ARRAY_CONTAINS_OP,
     190             :                                                            typentry);
     191             :             else
     192           0 :                 selec = mcelem_array_contained_selec(NULL, 0,
     193             :                                                      NULL, 0,
     194             :                                                      &constval, 1,
     195             :                                                      NULL, 0,
     196             :                                                      OID_ARRAY_CONTAINED_OP,
     197             :                                                      typentry);
     198             :         }
     199             : 
     200             :         /*
     201             :          * MCE stats count only non-null rows, so adjust for null rows.
     202             :          */
     203          12 :         selec *= (1.0 - stats->stanullfrac);
     204             :     }
     205             :     else
     206             :     {
     207             :         /* No stats at all, so do without */
     208         106 :         if (useOr)
     209         106 :             selec = mcelem_array_contain_overlap_selec(NULL, 0,
     210             :                                                        NULL, 0,
     211             :                                                        &constval, 1,
     212             :                                                        OID_ARRAY_CONTAINS_OP,
     213             :                                                        typentry);
     214             :         else
     215           0 :             selec = mcelem_array_contained_selec(NULL, 0,
     216             :                                                  NULL, 0,
     217             :                                                  &constval, 1,
     218             :                                                  NULL, 0,
     219             :                                                  OID_ARRAY_CONTAINED_OP,
     220             :                                                  typentry);
     221             :         /* we assume no nulls here, so no stanullfrac correction */
     222             :     }
     223             : 
     224         118 :     ReleaseVariableStats(vardata);
     225             : 
     226             :     /*
     227             :      * If the operator is <>, invert the results.
     228             :      */
     229         118 :     if (!isEquality)
     230          86 :         selec = 1.0 - selec;
     231             : 
     232         118 :     CLAMP_PROBABILITY(selec);
     233             : 
     234         118 :     return selec;
     235             : }
     236             : 
     237             : /*
     238             :  * arraycontsel -- restriction selectivity for array @>, &&, <@ operators
     239             :  */
     240             : Datum
     241         974 : arraycontsel(PG_FUNCTION_ARGS)
     242             : {
     243         974 :     PlannerInfo *root = (PlannerInfo *) PG_GETARG_POINTER(0);
     244         974 :     Oid         operator = PG_GETARG_OID(1);
     245         974 :     List       *args = (List *) PG_GETARG_POINTER(2);
     246         974 :     int         varRelid = PG_GETARG_INT32(3);
     247             :     VariableStatData vardata;
     248             :     Node       *other;
     249             :     bool        varonleft;
     250             :     Selectivity selec;
     251             :     Oid         element_typeid;
     252             : 
     253             :     /*
     254             :      * If expression is not (variable op something) or (something op
     255             :      * variable), then punt and return a default estimate.
     256             :      */
     257         974 :     if (!get_restriction_variable(root, args, varRelid,
     258             :                                   &vardata, &other, &varonleft))
     259           0 :         PG_RETURN_FLOAT8(DEFAULT_SEL(operator));
     260             : 
     261             :     /*
     262             :      * Can't do anything useful if the something is not a constant, either.
     263             :      */
     264         974 :     if (!IsA(other, Const))
     265             :     {
     266           0 :         ReleaseVariableStats(vardata);
     267           0 :         PG_RETURN_FLOAT8(DEFAULT_SEL(operator));
     268             :     }
     269             : 
     270             :     /*
     271             :      * The "&&", "@>" and "<@" operators are strict, so we can cope with a
     272             :      * NULL constant right away.
     273             :      */
     274         974 :     if (((Const *) other)->constisnull)
     275             :     {
     276           0 :         ReleaseVariableStats(vardata);
     277           0 :         PG_RETURN_FLOAT8(0.0);
     278             :     }
     279             : 
     280             :     /*
     281             :      * If var is on the right, commute the operator, so that we can assume the
     282             :      * var is on the left in what follows.
     283             :      */
     284         974 :     if (!varonleft)
     285             :     {
     286          24 :         if (operator == OID_ARRAY_CONTAINS_OP)
     287           0 :             operator = OID_ARRAY_CONTAINED_OP;
     288          24 :         else if (operator == OID_ARRAY_CONTAINED_OP)
     289          24 :             operator = OID_ARRAY_CONTAINS_OP;
     290             :     }
     291             : 
     292             :     /*
     293             :      * OK, there's a Var and a Const we're dealing with here.  We need the
     294             :      * Const to be an array with same element type as column, else we can't do
     295             :      * anything useful.  (Such cases will likely fail at runtime, but here
     296             :      * we'd rather just return a default estimate.)
     297             :      */
     298         974 :     element_typeid = get_base_element_type(((Const *) other)->consttype);
     299        1948 :     if (element_typeid != InvalidOid &&
     300         974 :         element_typeid == get_base_element_type(vardata.vartype))
     301             :     {
     302         974 :         selec = calc_arraycontsel(&vardata, ((Const *) other)->constvalue,
     303             :                                   element_typeid, operator);
     304             :     }
     305             :     else
     306             :     {
     307           0 :         selec = DEFAULT_SEL(operator);
     308             :     }
     309             : 
     310         974 :     ReleaseVariableStats(vardata);
     311             : 
     312         974 :     CLAMP_PROBABILITY(selec);
     313             : 
     314         974 :     PG_RETURN_FLOAT8((float8) selec);
     315             : }
     316             : 
     317             : /*
     318             :  * arraycontjoinsel -- join selectivity for array @>, &&, <@ operators
     319             :  */
     320             : Datum
     321         304 : arraycontjoinsel(PG_FUNCTION_ARGS)
     322             : {
     323             :     /* For the moment this is just a stub */
     324         304 :     Oid         operator = PG_GETARG_OID(1);
     325             : 
     326         304 :     PG_RETURN_FLOAT8(DEFAULT_SEL(operator));
     327             : }
     328             : 
     329             : /*
     330             :  * Calculate selectivity for "arraycolumn @> const", "arraycolumn && const"
     331             :  * or "arraycolumn <@ const" based on the statistics
     332             :  *
     333             :  * This function is mainly responsible for extracting the pg_statistic data
     334             :  * to be used; we then pass the problem on to mcelem_array_selec().
     335             :  */
     336             : static Selectivity
     337         974 : calc_arraycontsel(VariableStatData *vardata, Datum constval,
     338             :                   Oid elemtype, Oid operator)
     339             : {
     340             :     Selectivity selec;
     341             :     TypeCacheEntry *typentry;
     342             :     FmgrInfo   *cmpfunc;
     343             :     ArrayType  *array;
     344             : 
     345             :     /* Get element type's default comparison function */
     346         974 :     typentry = lookup_type_cache(elemtype, TYPECACHE_CMP_PROC_FINFO);
     347         974 :     if (!OidIsValid(typentry->cmp_proc_finfo.fn_oid))
     348           0 :         return DEFAULT_SEL(operator);
     349         974 :     cmpfunc = &typentry->cmp_proc_finfo;
     350             : 
     351             :     /*
     352             :      * The caller made sure the const is an array with same element type, so
     353             :      * get it now
     354             :      */
     355         974 :     array = DatumGetArrayTypeP(constval);
     356             : 
     357        1442 :     if (HeapTupleIsValid(vardata->statsTuple) &&
     358         468 :         statistic_proc_security_check(vardata, cmpfunc->fn_oid))
     359         468 :     {
     360             :         Form_pg_statistic stats;
     361             :         AttStatsSlot sslot;
     362             :         AttStatsSlot hslot;
     363             : 
     364         468 :         stats = (Form_pg_statistic) GETSTRUCT(vardata->statsTuple);
     365             : 
     366             :         /* MCELEM will be an array of same type as column */
     367         468 :         if (get_attstatsslot(&sslot, vardata->statsTuple,
     368             :                              STATISTIC_KIND_MCELEM, InvalidOid,
     369             :                              ATTSTATSSLOT_VALUES | ATTSTATSSLOT_NUMBERS))
     370             :         {
     371             :             /*
     372             :              * For "array <@ const" case we also need histogram of distinct
     373             :              * element counts.
     374             :              */
     375         468 :             if (operator != OID_ARRAY_CONTAINED_OP ||
     376          72 :                 !get_attstatsslot(&hslot, vardata->statsTuple,
     377             :                                   STATISTIC_KIND_DECHIST, InvalidOid,
     378             :                                   ATTSTATSSLOT_NUMBERS))
     379         396 :                 memset(&hslot, 0, sizeof(hslot));
     380             : 
     381             :             /* Use the most-common-elements slot for the array Var. */
     382         468 :             selec = mcelem_array_selec(array, typentry,
     383             :                                        sslot.values, sslot.nvalues,
     384             :                                        sslot.numbers, sslot.nnumbers,
     385             :                                        hslot.numbers, hslot.nnumbers,
     386             :                                        operator);
     387             : 
     388         468 :             free_attstatsslot(&hslot);
     389         468 :             free_attstatsslot(&sslot);
     390             :         }
     391             :         else
     392             :         {
     393             :             /* No most-common-elements info, so do without */
     394           0 :             selec = mcelem_array_selec(array, typentry,
     395             :                                        NULL, 0, NULL, 0, NULL, 0,
     396             :                                        operator);
     397             :         }
     398             : 
     399             :         /*
     400             :          * MCE stats count only non-null rows, so adjust for null rows.
     401             :          */
     402         468 :         selec *= (1.0 - stats->stanullfrac);
     403             :     }
     404             :     else
     405             :     {
     406             :         /* No stats at all, so do without */
     407         506 :         selec = mcelem_array_selec(array, typentry,
     408             :                                    NULL, 0, NULL, 0, NULL, 0,
     409             :                                    operator);
     410             :         /* we assume no nulls here, so no stanullfrac correction */
     411             :     }
     412             : 
     413             :     /* If constant was toasted, release the copy we made */
     414         974 :     if (PointerGetDatum(array) != constval)
     415           0 :         pfree(array);
     416             : 
     417         974 :     return selec;
     418             : }
     419             : 
     420             : /*
     421             :  * Array selectivity estimation based on most common elements statistics
     422             :  *
     423             :  * This function just deconstructs and sorts the array constant's contents,
     424             :  * and then passes the problem on to mcelem_array_contain_overlap_selec or
     425             :  * mcelem_array_contained_selec depending on the operator.
     426             :  */
     427             : static Selectivity
     428         974 : mcelem_array_selec(ArrayType *array, TypeCacheEntry *typentry,
     429             :                    Datum *mcelem, int nmcelem,
     430             :                    float4 *numbers, int nnumbers,
     431             :                    float4 *hist, int nhist,
     432             :                    Oid operator)
     433             : {
     434             :     Selectivity selec;
     435             :     int         num_elems;
     436             :     Datum      *elem_values;
     437             :     bool       *elem_nulls;
     438             :     bool        null_present;
     439             :     int         nonnull_nitems;
     440             :     int         i;
     441             : 
     442             :     /*
     443             :      * Prepare constant array data for sorting.  Sorting lets us find unique
     444             :      * elements and efficiently merge with the MCELEM array.
     445             :      */
     446         974 :     deconstruct_array(array,
     447             :                       typentry->type_id,
     448         974 :                       typentry->typlen,
     449         974 :                       typentry->typbyval,
     450         974 :                       typentry->typalign,
     451             :                       &elem_values, &elem_nulls, &num_elems);
     452             : 
     453             :     /* Collapse out any null elements */
     454         974 :     nonnull_nitems = 0;
     455         974 :     null_present = false;
     456        1914 :     for (i = 0; i < num_elems; i++)
     457             :     {
     458         940 :         if (elem_nulls[i])
     459          36 :             null_present = true;
     460             :         else
     461         904 :             elem_values[nonnull_nitems++] = elem_values[i];
     462             :     }
     463             : 
     464             :     /*
     465             :      * Query "column @> '{anything, null}'" matches nothing.  For the other
     466             :      * two operators, presence of a null in the constant can be ignored.
     467             :      */
     468         974 :     if (null_present && operator == OID_ARRAY_CONTAINS_OP)
     469             :     {
     470          12 :         pfree(elem_values);
     471          12 :         pfree(elem_nulls);
     472          12 :         return (Selectivity) 0.0;
     473             :     }
     474             : 
     475             :     /* Sort extracted elements using their default comparison function. */
     476         962 :     qsort_arg(elem_values, nonnull_nitems, sizeof(Datum),
     477             :               element_compare, typentry);
     478             : 
     479             :     /* Separate cases according to operator */
     480         962 :     if (operator == OID_ARRAY_CONTAINS_OP || operator == OID_ARRAY_OVERLAP_OP)
     481         888 :         selec = mcelem_array_contain_overlap_selec(mcelem, nmcelem,
     482             :                                                    numbers, nnumbers,
     483             :                                                    elem_values, nonnull_nitems,
     484             :                                                    operator, typentry);
     485          74 :     else if (operator == OID_ARRAY_CONTAINED_OP)
     486          74 :         selec = mcelem_array_contained_selec(mcelem, nmcelem,
     487             :                                              numbers, nnumbers,
     488             :                                              elem_values, nonnull_nitems,
     489             :                                              hist, nhist,
     490             :                                              operator, typentry);
     491             :     else
     492             :     {
     493           0 :         elog(ERROR, "arraycontsel called for unrecognized operator %u",
     494             :              operator);
     495             :         selec = 0.0;            /* keep compiler quiet */
     496             :     }
     497             : 
     498         962 :     pfree(elem_values);
     499         962 :     pfree(elem_nulls);
     500         962 :     return selec;
     501             : }
     502             : 
     503             : /*
     504             :  * Estimate selectivity of "column @> const" and "column && const" based on
     505             :  * most common element statistics.  This estimation assumes element
     506             :  * occurrences are independent.
     507             :  *
     508             :  * mcelem (of length nmcelem) and numbers (of length nnumbers) are from
     509             :  * the array column's MCELEM statistics slot, or are NULL/0 if stats are
     510             :  * not available.  array_data (of length nitems) is the constant's elements.
     511             :  *
     512             :  * Both the mcelem and array_data arrays are assumed presorted according
     513             :  * to the element type's cmpfunc.  Null elements are not present.
     514             :  *
     515             :  * TODO: this estimate probably could be improved by using the distinct
     516             :  * elements count histogram.  For example, excepting the special case of
     517             :  * "column @> '{}'", we can multiply the calculated selectivity by the
     518             :  * fraction of nonempty arrays in the column.
     519             :  */
     520             : static Selectivity
     521        1006 : mcelem_array_contain_overlap_selec(Datum *mcelem, int nmcelem,
     522             :                                    float4 *numbers, int nnumbers,
     523             :                                    Datum *array_data, int nitems,
     524             :                                    Oid operator, TypeCacheEntry *typentry)
     525             : {
     526             :     Selectivity selec,
     527             :                 elem_selec;
     528             :     int         mcelem_index,
     529             :                 i;
     530             :     bool        use_bsearch;
     531             :     float4      minfreq;
     532             : 
     533             :     /*
     534             :      * There should be three more Numbers than Values, because the last three
     535             :      * cells should hold minimal and maximal frequency among the non-null
     536             :      * elements, and then the frequency of null elements.  Ignore the Numbers
     537             :      * if not right.
     538             :      */
     539        1006 :     if (nnumbers != nmcelem + 3)
     540             :     {
     541         610 :         numbers = NULL;
     542         610 :         nnumbers = 0;
     543             :     }
     544             : 
     545        1006 :     if (numbers)
     546             :     {
     547             :         /* Grab the lowest observed frequency */
     548         396 :         minfreq = numbers[nmcelem];
     549             :     }
     550             :     else
     551             :     {
     552             :         /* Without statistics make some default assumptions */
     553         610 :         minfreq = 2 * (float4) DEFAULT_CONTAIN_SEL;
     554             :     }
     555             : 
     556             :     /* Decide whether it is faster to use binary search or not. */
     557        1006 :     if (nitems * floor_log2((uint32) nmcelem) < nmcelem + nitems)
     558         808 :         use_bsearch = true;
     559             :     else
     560         198 :         use_bsearch = false;
     561             : 
     562        1006 :     if (operator == OID_ARRAY_CONTAINS_OP)
     563             :     {
     564             :         /*
     565             :          * Initial selectivity for "column @> const" query is 1.0, and it will
     566             :          * be decreased with each element of constant array.
     567             :          */
     568         860 :         selec = 1.0;
     569             :     }
     570             :     else
     571             :     {
     572             :         /*
     573             :          * Initial selectivity for "column && const" query is 0.0, and it will
     574             :          * be increased with each element of constant array.
     575             :          */
     576         146 :         selec = 0.0;
     577             :     }
     578             : 
     579             :     /* Scan mcelem and array in parallel. */
     580        1006 :     mcelem_index = 0;
     581        1866 :     for (i = 0; i < nitems; i++)
     582             :     {
     583         860 :         bool        match = false;
     584             : 
     585             :         /* Ignore any duplicates in the array data. */
     586         990 :         if (i > 0 &&
     587         130 :             element_compare(&array_data[i - 1], &array_data[i], typentry) == 0)
     588           0 :             continue;
     589             : 
     590             :         /* Find the smallest MCELEM >= this array item. */
     591         860 :         if (use_bsearch)
     592             :         {
     593         860 :             match = find_next_mcelem(mcelem, nmcelem, array_data[i],
     594             :                                      &mcelem_index, typentry);
     595             :         }
     596             :         else
     597             :         {
     598           0 :             while (mcelem_index < nmcelem)
     599             :             {
     600           0 :                 int         cmp = element_compare(&mcelem[mcelem_index],
     601           0 :                                                   &array_data[i],
     602             :                                                   typentry);
     603             : 
     604           0 :                 if (cmp < 0)
     605           0 :                     mcelem_index++;
     606             :                 else
     607             :                 {
     608           0 :                     if (cmp == 0)
     609           0 :                         match = true;   /* mcelem is found */
     610           0 :                     break;
     611             :                 }
     612             :             }
     613             :         }
     614             : 
     615         860 :         if (match && numbers)
     616             :         {
     617             :             /* MCELEM matches the array item; use its frequency. */
     618         408 :             elem_selec = numbers[mcelem_index];
     619         408 :             mcelem_index++;
     620             :         }
     621             :         else
     622             :         {
     623             :             /*
     624             :              * The element is not in MCELEM.  Punt, but assume that the
     625             :              * selectivity cannot be more than minfreq / 2.
     626             :              */
     627         452 :             elem_selec = Min(DEFAULT_CONTAIN_SEL, minfreq / 2);
     628             :         }
     629             : 
     630             :         /*
     631             :          * Update overall selectivity using the current element's selectivity
     632             :          * and an assumption of element occurrence independence.
     633             :          */
     634         860 :         if (operator == OID_ARRAY_CONTAINS_OP)
     635         712 :             selec *= elem_selec;
     636             :         else
     637         148 :             selec = selec + elem_selec - selec * elem_selec;
     638             : 
     639             :         /* Clamp intermediate results to stay sane despite roundoff error */
     640         860 :         CLAMP_PROBABILITY(selec);
     641             :     }
     642             : 
     643        1006 :     return selec;
     644             : }
     645             : 
     646             : /*
     647             :  * Estimate selectivity of "column <@ const" based on most common element
     648             :  * statistics.
     649             :  *
     650             :  * mcelem (of length nmcelem) and numbers (of length nnumbers) are from
     651             :  * the array column's MCELEM statistics slot, or are NULL/0 if stats are
     652             :  * not available.  array_data (of length nitems) is the constant's elements.
     653             :  * hist (of length nhist) is from the array column's DECHIST statistics slot,
     654             :  * or is NULL/0 if those stats are not available.
     655             :  *
     656             :  * Both the mcelem and array_data arrays are assumed presorted according
     657             :  * to the element type's cmpfunc.  Null elements are not present.
     658             :  *
     659             :  * Independent element occurrence would imply a particular distribution of
     660             :  * distinct element counts among matching rows.  Real data usually falsifies
     661             :  * that assumption.  For example, in a set of 11-element integer arrays having
     662             :  * elements in the range [0..10], element occurrences are typically not
     663             :  * independent.  If they were, a sufficiently-large set would include all
     664             :  * distinct element counts 0 through 11.  We correct for this using the
     665             :  * histogram of distinct element counts.
     666             :  *
     667             :  * In the "column @> const" and "column && const" cases, we usually have a
     668             :  * "const" with low number of elements (otherwise we have selectivity close
     669             :  * to 0 or 1 respectively).  That's why the effect of dependence related
     670             :  * to distinct element count distribution is negligible there.  In the
     671             :  * "column <@ const" case, number of elements is usually high (otherwise we
     672             :  * have selectivity close to 0).  That's why we should do a correction with
     673             :  * the array distinct element count distribution here.
     674             :  *
     675             :  * Using the histogram of distinct element counts produces a different
     676             :  * distribution law than independent occurrences of elements.  This
     677             :  * distribution law can be described as follows:
     678             :  *
     679             :  * P(o1, o2, ..., on) = f1^o1 * (1 - f1)^(1 - o1) * f2^o2 *
     680             :  *    (1 - f2)^(1 - o2) * ... * fn^on * (1 - fn)^(1 - on) * hist[m] / ind[m]
     681             :  *
     682             :  * where:
     683             :  * o1, o2, ..., on - occurrences of elements 1, 2, ..., n
     684             :  *      (1 - occurrence, 0 - no occurrence) in row
     685             :  * f1, f2, ..., fn - frequencies of elements 1, 2, ..., n
     686             :  *      (scalar values in [0..1]) according to collected statistics
     687             :  * m = o1 + o2 + ... + on = total number of distinct elements in row
     688             :  * hist[m] - histogram data for occurrence of m elements.
     689             :  * ind[m] - probability of m occurrences from n events assuming their
     690             :  *    probabilities to be equal to frequencies of array elements.
     691             :  *
     692             :  * ind[m] = sum(f1^o1 * (1 - f1)^(1 - o1) * f2^o2 * (1 - f2)^(1 - o2) *
     693             :  * ... * fn^on * (1 - fn)^(1 - on), o1, o2, ..., on) | o1 + o2 + .. on = m
     694             :  */
     695             : static Selectivity
     696          74 : mcelem_array_contained_selec(Datum *mcelem, int nmcelem,
     697             :                              float4 *numbers, int nnumbers,
     698             :                              Datum *array_data, int nitems,
     699             :                              float4 *hist, int nhist,
     700             :                              Oid operator, TypeCacheEntry *typentry)
     701             : {
     702             :     int         mcelem_index,
     703             :                 i,
     704          74 :                 unique_nitems = 0;
     705             :     float       selec,
     706             :                 minfreq,
     707             :                 nullelem_freq;
     708             :     float      *dist,
     709             :                *mcelem_dist,
     710             :                *hist_part;
     711             :     float       avg_count,
     712             :                 mult,
     713             :                 rest;
     714             :     float      *elem_selec;
     715             : 
     716             :     /*
     717             :      * There should be three more Numbers than Values in the MCELEM slot,
     718             :      * because the last three cells should hold minimal and maximal frequency
     719             :      * among the non-null elements, and then the frequency of null elements.
     720             :      * Punt if not right, because we can't do much without the element freqs.
     721             :      */
     722          74 :     if (numbers == NULL || nnumbers != nmcelem + 3)
     723           2 :         return DEFAULT_CONTAIN_SEL;
     724             : 
     725             :     /* Can't do much without a count histogram, either */
     726          72 :     if (hist == NULL || nhist < 3)
     727           0 :         return DEFAULT_CONTAIN_SEL;
     728             : 
     729             :     /*
     730             :      * Grab some of the summary statistics that compute_array_stats() stores:
     731             :      * lowest frequency, frequency of null elements, and average distinct
     732             :      * element count.
     733             :      */
     734          72 :     minfreq = numbers[nmcelem];
     735          72 :     nullelem_freq = numbers[nmcelem + 2];
     736          72 :     avg_count = hist[nhist - 1];
     737             : 
     738             :     /*
     739             :      * "rest" will be the sum of the frequencies of all elements not
     740             :      * represented in MCELEM.  The average distinct element count is the sum
     741             :      * of the frequencies of *all* elements.  Begin with that; we will proceed
     742             :      * to subtract the MCELEM frequencies.
     743             :      */
     744          72 :     rest = avg_count;
     745             : 
     746             :     /*
     747             :      * mult is a multiplier representing estimate of probability that each
     748             :      * mcelem that is not present in constant doesn't occur.
     749             :      */
     750          72 :     mult = 1.0f;
     751             : 
     752             :     /*
     753             :      * elem_selec is array of estimated frequencies for elements in the
     754             :      * constant.
     755             :      */
     756          72 :     elem_selec = (float *) palloc(sizeof(float) * nitems);
     757             : 
     758             :     /* Scan mcelem and array in parallel. */
     759          72 :     mcelem_index = 0;
     760         228 :     for (i = 0; i < nitems; i++)
     761             :     {
     762         156 :         bool        match = false;
     763             : 
     764             :         /* Ignore any duplicates in the array data. */
     765         276 :         if (i > 0 &&
     766         120 :             element_compare(&array_data[i - 1], &array_data[i], typentry) == 0)
     767           0 :             continue;
     768             : 
     769             :         /*
     770             :          * Iterate over MCELEM until we find an entry greater than or equal to
     771             :          * this element of the constant.  Update "rest" and "mult" for mcelem
     772             :          * entries skipped over.
     773             :          */
     774        4128 :         while (mcelem_index < nmcelem)
     775             :         {
     776        4128 :             int         cmp = element_compare(&mcelem[mcelem_index],
     777        4128 :                                               &array_data[i],
     778             :                                               typentry);
     779             : 
     780        4128 :             if (cmp < 0)
     781             :             {
     782        3972 :                 mult *= (1.0f - numbers[mcelem_index]);
     783        3972 :                 rest -= numbers[mcelem_index];
     784        3972 :                 mcelem_index++;
     785             :             }
     786             :             else
     787             :             {
     788         156 :                 if (cmp == 0)
     789         156 :                     match = true;   /* mcelem is found */
     790         156 :                 break;
     791             :             }
     792             :         }
     793             : 
     794         156 :         if (match)
     795             :         {
     796             :             /* MCELEM matches the array item. */
     797         156 :             elem_selec[unique_nitems] = numbers[mcelem_index];
     798             :             /* "rest" is decremented for all mcelems, matched or not */
     799         156 :             rest -= numbers[mcelem_index];
     800         156 :             mcelem_index++;
     801             :         }
     802             :         else
     803             :         {
     804             :             /*
     805             :              * The element is not in MCELEM.  Punt, but assume that the
     806             :              * selectivity cannot be more than minfreq / 2.
     807             :              */
     808           0 :             elem_selec[unique_nitems] = Min(DEFAULT_CONTAIN_SEL,
     809             :                                             minfreq / 2);
     810             :         }
     811             : 
     812         156 :         unique_nitems++;
     813             :     }
     814             : 
     815             :     /*
     816             :      * If we handled all constant elements without exhausting the MCELEM
     817             :      * array, finish walking it to complete calculation of "rest" and "mult".
     818             :      */
     819        7668 :     while (mcelem_index < nmcelem)
     820             :     {
     821        7596 :         mult *= (1.0f - numbers[mcelem_index]);
     822        7596 :         rest -= numbers[mcelem_index];
     823        7596 :         mcelem_index++;
     824             :     }
     825             : 
     826             :     /*
     827             :      * The presence of many distinct rare elements materially decreases
     828             :      * selectivity.  Use the Poisson distribution to estimate the probability
     829             :      * of a column value having zero occurrences of such elements.  See above
     830             :      * for the definition of "rest".
     831             :      */
     832          72 :     mult *= exp(-rest);
     833             : 
     834             :     /*----------
     835             :      * Using the distinct element count histogram requires
     836             :      *      O(unique_nitems * (nmcelem + unique_nitems))
     837             :      * operations.  Beyond a certain computational cost threshold, it's
     838             :      * reasonable to sacrifice accuracy for decreased planning time.  We limit
     839             :      * the number of operations to EFFORT * nmcelem; since nmcelem is limited
     840             :      * by the column's statistics target, the work done is user-controllable.
     841             :      *
     842             :      * If the number of operations would be too large, we can reduce it
     843             :      * without losing all accuracy by reducing unique_nitems and considering
     844             :      * only the most-common elements of the constant array.  To make the
     845             :      * results exactly match what we would have gotten with only those
     846             :      * elements to start with, we'd have to remove any discarded elements'
     847             :      * frequencies from "mult", but since this is only an approximation
     848             :      * anyway, we don't bother with that.  Therefore it's sufficient to qsort
     849             :      * elem_selec[] and take the largest elements.  (They will no longer match
     850             :      * up with the elements of array_data[], but we don't care.)
     851             :      *----------
     852             :      */
     853             : #define EFFORT 100
     854             : 
     855          72 :     if ((nmcelem + unique_nitems) > 0 &&
     856          72 :         unique_nitems > EFFORT * nmcelem / (nmcelem + unique_nitems))
     857             :     {
     858             :         /*
     859             :          * Use the quadratic formula to solve for largest allowable N.  We
     860             :          * have A = 1, B = nmcelem, C = - EFFORT * nmcelem.
     861             :          */
     862           0 :         double      b = (double) nmcelem;
     863             :         int         n;
     864             : 
     865           0 :         n = (int) ((sqrt(b * b + 4 * EFFORT * b) - b) / 2);
     866             : 
     867             :         /* Sort, then take just the first n elements */
     868           0 :         qsort(elem_selec, unique_nitems, sizeof(float),
     869             :               float_compare_desc);
     870           0 :         unique_nitems = n;
     871             :     }
     872             : 
     873             :     /*
     874             :      * Calculate probabilities of each distinct element count for both mcelems
     875             :      * and constant elements.  At this point, assume independent element
     876             :      * occurrence.
     877             :      */
     878          72 :     dist = calc_distr(elem_selec, unique_nitems, unique_nitems, 0.0f);
     879          72 :     mcelem_dist = calc_distr(numbers, nmcelem, unique_nitems, rest);
     880             : 
     881             :     /* ignore hist[nhist-1], which is the average not a histogram member */
     882          72 :     hist_part = calc_hist(hist, nhist - 1, unique_nitems);
     883             : 
     884          72 :     selec = 0.0f;
     885         300 :     for (i = 0; i <= unique_nitems; i++)
     886             :     {
     887             :         /*
     888             :          * mult * dist[i] / mcelem_dist[i] gives us probability of qual
     889             :          * matching from assumption of independent element occurrence with the
     890             :          * condition that distinct element count = i.
     891             :          */
     892         228 :         if (mcelem_dist[i] > 0)
     893         228 :             selec += hist_part[i] * mult * dist[i] / mcelem_dist[i];
     894             :     }
     895             : 
     896          72 :     pfree(dist);
     897          72 :     pfree(mcelem_dist);
     898          72 :     pfree(hist_part);
     899          72 :     pfree(elem_selec);
     900             : 
     901             :     /* Take into account occurrence of NULL element. */
     902          72 :     selec *= (1.0f - nullelem_freq);
     903             : 
     904          72 :     CLAMP_PROBABILITY(selec);
     905             : 
     906          72 :     return selec;
     907             : }
     908             : 
     909             : /*
     910             :  * Calculate the first n distinct element count probabilities from a
     911             :  * histogram of distinct element counts.
     912             :  *
     913             :  * Returns a palloc'd array of n+1 entries, with array[k] being the
     914             :  * probability of element count k, k in [0..n].
     915             :  *
     916             :  * We assume that a histogram box with bounds a and b gives 1 / ((b - a + 1) *
     917             :  * (nhist - 1)) probability to each value in (a,b) and an additional half of
     918             :  * that to a and b themselves.
     919             :  */
     920             : static float *
     921          72 : calc_hist(const float4 *hist, int nhist, int n)
     922             : {
     923             :     float      *hist_part;
     924             :     int         k,
     925          72 :                 i = 0;
     926          72 :     float       prev_interval = 0,
     927             :                 next_interval;
     928             :     float       frac;
     929             : 
     930          72 :     hist_part = (float *) palloc((n + 1) * sizeof(float));
     931             : 
     932             :     /*
     933             :      * frac is a probability contribution for each interval between histogram
     934             :      * values.  We have nhist - 1 intervals, so contribution of each one will
     935             :      * be 1 / (nhist - 1).
     936             :      */
     937          72 :     frac = 1.0f / ((float) (nhist - 1));
     938             : 
     939         300 :     for (k = 0; k <= n; k++)
     940             :     {
     941         228 :         int         count = 0;
     942             : 
     943             :         /*
     944             :          * Count the histogram boundaries equal to k.  (Although the histogram
     945             :          * should theoretically contain only exact integers, entries are
     946             :          * floats so there could be roundoff error in large values.  Treat any
     947             :          * fractional value as equal to the next larger k.)
     948             :          */
     949        2016 :         while (i < nhist && hist[i] <= k)
     950             :         {
     951        1788 :             count++;
     952        1788 :             i++;
     953             :         }
     954             : 
     955         228 :         if (count > 0)
     956             :         {
     957             :             /* k is an exact bound for at least one histogram box. */
     958             :             float       val;
     959             : 
     960             :             /* Find length between current histogram value and the next one */
     961         216 :             if (i < nhist)
     962         216 :                 next_interval = hist[i] - hist[i - 1];
     963             :             else
     964           0 :                 next_interval = 0;
     965             : 
     966             :             /*
     967             :              * count - 1 histogram boxes contain k exclusively.  They
     968             :              * contribute a total of (count - 1) * frac probability.  Also
     969             :              * factor in the partial histogram boxes on either side.
     970             :              */
     971         216 :             val = (float) (count - 1);
     972         216 :             if (next_interval > 0)
     973         216 :                 val += 0.5f / next_interval;
     974         216 :             if (prev_interval > 0)
     975         144 :                 val += 0.5f / prev_interval;
     976         216 :             hist_part[k] = frac * val;
     977             : 
     978         216 :             prev_interval = next_interval;
     979             :         }
     980             :         else
     981             :         {
     982             :             /* k does not appear as an exact histogram bound. */
     983          12 :             if (prev_interval > 0)
     984          12 :                 hist_part[k] = frac / prev_interval;
     985             :             else
     986           0 :                 hist_part[k] = 0.0f;
     987             :         }
     988             :     }
     989             : 
     990          72 :     return hist_part;
     991             : }
     992             : 
     993             : /*
     994             :  * Consider n independent events with probabilities p[].  This function
     995             :  * calculates probabilities of exact k of events occurrence for k in [0..m].
     996             :  * Returns a palloc'd array of size m+1.
     997             :  *
     998             :  * "rest" is the sum of the probabilities of all low-probability events not
     999             :  * included in p.
    1000             :  *
    1001             :  * Imagine matrix M of size (n + 1) x (m + 1).  Element M[i,j] denotes the
    1002             :  * probability that exactly j of first i events occur.  Obviously M[0,0] = 1.
    1003             :  * For any constant j, each increment of i increases the probability iff the
    1004             :  * event occurs.  So, by the law of total probability:
    1005             :  *  M[i,j] = M[i - 1, j] * (1 - p[i]) + M[i - 1, j - 1] * p[i]
    1006             :  *      for i > 0, j > 0.
    1007             :  *  M[i,0] = M[i - 1, 0] * (1 - p[i]) for i > 0.
    1008             :  */
    1009             : static float *
    1010         144 : calc_distr(const float *p, int n, int m, float rest)
    1011             : {
    1012             :     float      *row,
    1013             :                *prev_row,
    1014             :                *tmp;
    1015             :     int         i,
    1016             :                 j;
    1017             : 
    1018             :     /*
    1019             :      * Since we return only the last row of the matrix and need only the
    1020             :      * current and previous row for calculations, allocate two rows.
    1021             :      */
    1022         144 :     row = (float *) palloc((m + 1) * sizeof(float));
    1023         144 :     prev_row = (float *) palloc((m + 1) * sizeof(float));
    1024             : 
    1025             :     /* M[0,0] = 1 */
    1026         144 :     row[0] = 1.0f;
    1027       12024 :     for (i = 1; i <= n; i++)
    1028             :     {
    1029       11880 :         float       t = p[i - 1];
    1030             : 
    1031             :         /* Swap rows */
    1032       11880 :         tmp = row;
    1033       11880 :         row = prev_row;
    1034       11880 :         prev_row = tmp;
    1035             : 
    1036             :         /* Calculate next row */
    1037       53148 :         for (j = 0; j <= i && j <= m; j++)
    1038             :         {
    1039       41268 :             float       val = 0.0f;
    1040             : 
    1041       41268 :             if (j < i)
    1042       40956 :                 val += prev_row[j] * (1.0f - t);
    1043       41268 :             if (j > 0)
    1044       29388 :                 val += prev_row[j - 1] * t;
    1045       41268 :             row[j] = val;
    1046             :         }
    1047             :     }
    1048             : 
    1049             :     /*
    1050             :      * The presence of many distinct rare (not in "p") elements materially
    1051             :      * decreases selectivity.  Model their collective occurrence with the
    1052             :      * Poisson distribution.
    1053             :      */
    1054         144 :     if (rest > DEFAULT_CONTAIN_SEL)
    1055             :     {
    1056             :         float       t;
    1057             : 
    1058             :         /* Swap rows */
    1059           0 :         tmp = row;
    1060           0 :         row = prev_row;
    1061           0 :         prev_row = tmp;
    1062             : 
    1063           0 :         for (i = 0; i <= m; i++)
    1064           0 :             row[i] = 0.0f;
    1065             : 
    1066             :         /* Value of Poisson distribution for 0 occurrences */
    1067           0 :         t = exp(-rest);
    1068             : 
    1069             :         /*
    1070             :          * Calculate convolution of previously computed distribution and the
    1071             :          * Poisson distribution.
    1072             :          */
    1073           0 :         for (i = 0; i <= m; i++)
    1074             :         {
    1075           0 :             for (j = 0; j <= m - i; j++)
    1076           0 :                 row[j + i] += prev_row[j] * t;
    1077             : 
    1078             :             /* Get Poisson distribution value for (i + 1) occurrences */
    1079           0 :             t *= rest / (float) (i + 1);
    1080             :         }
    1081             :     }
    1082             : 
    1083         144 :     pfree(prev_row);
    1084         144 :     return row;
    1085             : }
    1086             : 
    1087             : /* Fast function for floor value of 2 based logarithm calculation. */
    1088             : static int
    1089        1006 : floor_log2(uint32 n)
    1090             : {
    1091        1006 :     int         logval = 0;
    1092             : 
    1093        1006 :     if (n == 0)
    1094         610 :         return -1;
    1095         396 :     if (n >= (1 << 16))
    1096             :     {
    1097           0 :         n >>= 16;
    1098           0 :         logval += 16;
    1099             :     }
    1100         396 :     if (n >= (1 << 8))
    1101             :     {
    1102         120 :         n >>= 8;
    1103         120 :         logval += 8;
    1104             :     }
    1105         396 :     if (n >= (1 << 4))
    1106             :     {
    1107         276 :         n >>= 4;
    1108         276 :         logval += 4;
    1109             :     }
    1110         396 :     if (n >= (1 << 2))
    1111             :     {
    1112         264 :         n >>= 2;
    1113         264 :         logval += 2;
    1114             :     }
    1115         396 :     if (n >= (1 << 1))
    1116             :     {
    1117         186 :         logval += 1;
    1118             :     }
    1119         396 :     return logval;
    1120             : }
    1121             : 
    1122             : /*
    1123             :  * find_next_mcelem binary-searches a most common elements array, starting
    1124             :  * from *index, for the first member >= value.  It saves the position of the
    1125             :  * match into *index and returns true if it's an exact match.  (Note: we
    1126             :  * assume the mcelem elements are distinct so there can't be more than one
    1127             :  * exact match.)
    1128             :  */
    1129             : static bool
    1130         860 : find_next_mcelem(Datum *mcelem, int nmcelem, Datum value, int *index,
    1131             :                  TypeCacheEntry *typentry)
    1132             : {
    1133         860 :     int         l = *index,
    1134         860 :                 r = nmcelem - 1,
    1135             :                 i,
    1136             :                 res;
    1137             : 
    1138        3344 :     while (l <= r)
    1139             :     {
    1140        2892 :         i = (l + r) / 2;
    1141        2892 :         res = element_compare(&mcelem[i], &value, typentry);
    1142        2892 :         if (res == 0)
    1143             :         {
    1144         408 :             *index = i;
    1145         408 :             return true;
    1146             :         }
    1147        2484 :         else if (res < 0)
    1148         882 :             l = i + 1;
    1149             :         else
    1150        1602 :             r = i - 1;
    1151             :     }
    1152         452 :     *index = l;
    1153         452 :     return false;
    1154             : }
    1155             : 
    1156             : /*
    1157             :  * Comparison function for elements.
    1158             :  *
    1159             :  * We use the element type's default btree opclass, and its default collation
    1160             :  * if the type is collation-sensitive.
    1161             :  *
    1162             :  * XXX consider using SortSupport infrastructure
    1163             :  */
    1164             : static int
    1165        7634 : element_compare(const void *key1, const void *key2, void *arg)
    1166             : {
    1167        7634 :     Datum       d1 = *((const Datum *) key1);
    1168        7634 :     Datum       d2 = *((const Datum *) key2);
    1169        7634 :     TypeCacheEntry *typentry = (TypeCacheEntry *) arg;
    1170        7634 :     FmgrInfo   *cmpfunc = &typentry->cmp_proc_finfo;
    1171             :     Datum       c;
    1172             : 
    1173        7634 :     c = FunctionCall2Coll(cmpfunc, typentry->typcollation, d1, d2);
    1174        7634 :     return DatumGetInt32(c);
    1175             : }
    1176             : 
    1177             : /*
    1178             :  * Comparison function for sorting floats into descending order.
    1179             :  */
    1180             : static int
    1181           0 : float_compare_desc(const void *key1, const void *key2)
    1182             : {
    1183           0 :     float       d1 = *((const float *) key1);
    1184           0 :     float       d2 = *((const float *) key2);
    1185             : 
    1186           0 :     if (d1 > d2)
    1187           0 :         return -1;
    1188           0 :     else if (d1 < d2)
    1189           0 :         return 1;
    1190             :     else
    1191           0 :         return 0;
    1192             : }

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