src/include/statistics/statistics.h

   1 /*-------------------------------------------------------------------------
   2  *
   3  * statistics.h
   4  *        Extended statistics and selectivity estimation functions.
   5  *
   6  * Portions Copyright (c) 1996-2025, PostgreSQL Global Development Group
   7  * Portions Copyright (c) 1994, Regents of the University of California
   8  *
   9  * src/include/statistics/statistics.h
  10  *
  11  *-------------------------------------------------------------------------
  12  */
  13 #ifndef STATISTICS_H
  14 #define STATISTICS_H
  15
  16 #include "commands/vacuum.h"
  17 #include "nodes/pathnodes.h"
  18
  19 #define STATS_MAX_DIMENSIONS    8       /* max number of attributes */
  20
  21 /* Multivariate distinct coefficients */
  22 #define STATS_NDISTINCT_MAGIC           0xA352BFA4      /* struct identifier */
  23 #define STATS_NDISTINCT_TYPE_BASIC      1       /* struct version */
  24
  25 /* MVNDistinctItem represents a single combination of columns */
  26 typedef struct MVNDistinctItem
  27 {
  28         double          ndistinct;              /* ndistinct value for this combination */
  29         int                     nattributes;    /* number of attributes */
  30         AttrNumber *attributes;         /* attribute numbers */
  31 } MVNDistinctItem;
  32
  33 /* A MVNDistinct object, comprising all possible combinations of columns */
  34 typedef struct MVNDistinct
  35 {
  36         uint32          magic;                  /* magic constant marker */
  37         uint32          type;                   /* type of ndistinct (BASIC) */
  38         uint32          nitems;                 /* number of items in the statistic */
  39         MVNDistinctItem items[FLEXIBLE_ARRAY_MEMBER];
  40 } MVNDistinct;
  41
  42 /* Multivariate functional dependencies */
  43 #define STATS_DEPS_MAGIC                0xB4549A2C      /* marks serialized bytea */
  44 #define STATS_DEPS_TYPE_BASIC   1       /* basic dependencies type */
  45
  46 /*
  47  * Functional dependencies, tracking column-level relationships (values
  48  * in one column determine values in another one).
  49  */
  50 typedef struct MVDependency
  51 {
  52         double          degree;                 /* degree of validity (0-1) */
  53         AttrNumber      nattributes;    /* number of attributes */
  54         AttrNumber      attributes[FLEXIBLE_ARRAY_MEMBER];      /* attribute numbers */
  55 } MVDependency;
  56
  57 typedef struct MVDependencies
  58 {
  59         uint32          magic;                  /* magic constant marker */
  60         uint32          type;                   /* type of MV Dependencies (BASIC) */
  61         uint32          ndeps;                  /* number of dependencies */
  62         MVDependency *deps[FLEXIBLE_ARRAY_MEMBER];      /* dependencies */
  63 } MVDependencies;
  64
  65 /* used to flag stats serialized to bytea */
  66 #define STATS_MCV_MAGIC                 0xE1A651C2      /* marks serialized bytea */
  67 #define STATS_MCV_TYPE_BASIC    1       /* basic MCV list type */
  68
  69 /* max items in MCV list */
  70 #define STATS_MCVLIST_MAX_ITEMS        MAX_STATISTICS_TARGET
  71
  72 /*
  73  * Multivariate MCV (most-common value) lists
  74  *
  75  * A straightforward extension of MCV items - i.e. a list (array) of
  76  * combinations of attribute values, together with a frequency and null flags.
  77  */
  78 typedef struct MCVItem
  79 {
  80         double          frequency;              /* frequency of this combination */
  81         double          base_frequency; /* frequency if independent */
  82         bool       *isnull;                     /* NULL flags */
  83         Datum      *values;                     /* item values */
  84 } MCVItem;
  85
  86 /* multivariate MCV list - essentially an array of MCV items */
  87 typedef struct MCVList
  88 {
  89         uint32          magic;                  /* magic constant marker */
  90         uint32          type;                   /* type of MCV list (BASIC) */
  91         uint32          nitems;                 /* number of MCV items in the array */
  92         AttrNumber      ndimensions;    /* number of dimensions */
  93         Oid                     types[STATS_MAX_DIMENSIONS];    /* OIDs of data types */
  94         MCVItem         items[FLEXIBLE_ARRAY_MEMBER];   /* array of MCV items */
  95 } MCVList;
  96
  97 extern MVNDistinct *statext_ndistinct_load(Oid mvoid, bool inh);
  98 extern MVDependencies *statext_dependencies_load(Oid mvoid, bool inh);
  99 extern MCVList *statext_mcv_load(Oid mvoid, bool inh);
 100
 101 extern void BuildRelationExtStatistics(Relation onerel, bool inh, double totalrows,
 102                                                                            int numrows, HeapTuple *rows,
 103                                                                            int natts, VacAttrStats **vacattrstats);
 104 extern int      ComputeExtStatisticsRows(Relation onerel,
 105                                                                          int natts, VacAttrStats **vacattrstats);
 106 extern bool statext_is_kind_built(HeapTuple htup, char type);
 107 extern Selectivity dependencies_clauselist_selectivity(PlannerInfo *root,
 108                                                                                                            List *clauses,
 109                                                                                                            int varRelid,
 110                                                                                                            JoinType jointype,
 111                                                                                                            SpecialJoinInfo *sjinfo,
 112                                                                                                            RelOptInfo *rel,
 113                                                                                                            Bitmapset **estimatedclauses);
 114 extern Selectivity statext_clauselist_selectivity(PlannerInfo *root,
 115                                                                                                   List *clauses,
 116                                                                                                   int varRelid,
 117                                                                                                   JoinType jointype,
 118                                                                                                   SpecialJoinInfo *sjinfo,
 119                                                                                                   RelOptInfo *rel,
 120                                                                                                   Bitmapset **estimatedclauses,
 121                                                                                                   bool is_or);
 122 extern bool has_stats_of_kind(List *stats, char requiredkind);
 123 extern StatisticExtInfo *choose_best_statistics(List *stats, char requiredkind,
 124                                                                                                 bool inh,
 125                                                                                                 Bitmapset **clause_attnums,
 126                                                                                                 List **clause_exprs,
 127                                                                                                 int nclauses);
 128 extern HeapTuple statext_expressions_load(Oid stxoid, bool inh, int idx);
 129
 130 #endif                                                  /* STATISTICS_H */