src/include/utils/selfuncs.h

   1 /*-------------------------------------------------------------------------
   2  *
   3  * selfuncs.h
   4  *        Selectivity functions and index cost estimation functions for
   5  *        standard operators and index access methods.
   6  *
   7  *
   8  * Portions Copyright (c) 1996-2009, PostgreSQL Global Development Group
   9  * Portions Copyright (c) 1994, Regents of the University of California
  10  *
  11  * $PostgreSQL$
  12  *
  13  *-------------------------------------------------------------------------
  14  */
  15 #ifndef SELFUNCS_H
  16 #define SELFUNCS_H
  17
  18 #include "fmgr.h"
  19 #include "access/htup.h"
  20 #include "nodes/relation.h"
  21
  22
  23 /*
  24  * Note: the default selectivity estimates are not chosen entirely at random.
  25  * We want them to be small enough to ensure that indexscans will be used if
  26  * available, for typical table densities of ~100 tuples/page.  Thus, for
  27  * example, 0.01 is not quite small enough, since that makes it appear that
  28  * nearly all pages will be hit anyway.  Also, since we sometimes estimate
  29  * eqsel as 1/num_distinct, we probably want DEFAULT_NUM_DISTINCT to equal
  30  * 1/DEFAULT_EQ_SEL.
  31  */
  32
  33 /* default selectivity estimate for equalities such as "A = b" */
  34 #define DEFAULT_EQ_SEL  0.005
  35
  36 /* default selectivity estimate for inequalities such as "A < b" */
  37 #define DEFAULT_INEQ_SEL  0.3333333333333333
  38
  39 /* default selectivity estimate for range inequalities "A > b AND A < c" */
  40 #define DEFAULT_RANGE_INEQ_SEL  0.005
  41
  42 /* default selectivity estimate for pattern-match operators such as LIKE */
  43 #define DEFAULT_MATCH_SEL       0.005
  44
  45 /* default number of distinct values in a table */
  46 #define DEFAULT_NUM_DISTINCT  200
  47
  48 /* default selectivity estimate for boolean and null test nodes */
  49 #define DEFAULT_UNK_SEL                 0.005
  50 #define DEFAULT_NOT_UNK_SEL             (1.0 - DEFAULT_UNK_SEL)
  51
  52
  53 /*
  54  * Clamp a computed probability estimate (which may suffer from roundoff or
  55  * estimation errors) to valid range.  Argument must be a float variable.
  56  */
  57 #define CLAMP_PROBABILITY(p) \
  58         do { \
  59                 if (p < 0.0) \
  60                         p = 0.0; \
  61                 else if (p > 1.0) \
  62                         p = 1.0; \
  63         } while (0)
  64
  65
  66 /* Return data from examine_variable and friends */
  67 typedef struct VariableStatData
  68 {
  69         Node       *var;                        /* the Var or expression tree */
  70         RelOptInfo *rel;                        /* Relation, or NULL if not identifiable */
  71         HeapTuple       statsTuple;             /* pg_statistic tuple, or NULL if none */
  72         /* NB: if statsTuple!=NULL, it must be freed when caller is done */
  73         void            (*freefunc) (HeapTuple tuple);  /* how to free statsTuple */
  74         Oid                     vartype;                /* exposed type of expression */
  75         Oid                     atttype;                /* type to pass to get_attstatsslot */
  76         int32           atttypmod;              /* typmod to pass to get_attstatsslot */
  77         bool            isunique;               /* true if matched to a unique index */
  78 } VariableStatData;
  79
  80 #define ReleaseVariableStats(vardata)  \
  81         do { \
  82                 if (HeapTupleIsValid((vardata).statsTuple)) \
  83                         (* (vardata).freefunc) ((vardata).statsTuple); \
  84         } while(0)
  85
  86
  87 typedef enum
  88 {
  89         Pattern_Type_Like, Pattern_Type_Like_IC,
  90         Pattern_Type_Regex, Pattern_Type_Regex_IC
  91 } Pattern_Type;
  92
  93 typedef enum
  94 {
  95         Pattern_Prefix_None, Pattern_Prefix_Partial, Pattern_Prefix_Exact
  96 } Pattern_Prefix_Status;
  97
  98
  99 /* selfuncs.c */
 100
 101 /* Hooks for plugins to get control when we ask for stats */
 102 typedef bool (*get_relation_stats_hook_type) (PlannerInfo *root,
 103                                                                                                                   RangeTblEntry *rte,
 104                                                                                                                   AttrNumber attnum,
 105                                                                                                   VariableStatData *vardata);
 106 extern PGDLLIMPORT get_relation_stats_hook_type get_relation_stats_hook;
 107 typedef bool (*get_index_stats_hook_type) (PlannerInfo *root,
 108                                                                                                            Oid indexOid,
 109                                                                                                            AttrNumber indexattnum,
 110                                                                                                   VariableStatData *vardata);
 111 extern PGDLLIMPORT get_index_stats_hook_type get_index_stats_hook;
 112
 113 extern void examine_variable(PlannerInfo *root, Node *node, int varRelid,
 114                                  VariableStatData *vardata);
 115 extern bool get_restriction_variable(PlannerInfo *root, List *args,
 116                                                  int varRelid,
 117                                                  VariableStatData *vardata, Node **other,
 118                                                  bool *varonleft);
 119 extern void get_join_variables(PlannerInfo *root, List *args,
 120                                    SpecialJoinInfo *sjinfo,
 121                                    VariableStatData *vardata1,
 122                                    VariableStatData *vardata2,
 123                                    bool *join_is_reversed);
 124 extern double get_variable_numdistinct(VariableStatData *vardata);
 125 extern double mcv_selectivity(VariableStatData *vardata, FmgrInfo *opproc,
 126                                 Datum constval, bool varonleft,
 127                                 double *sumcommonp);
 128 extern double histogram_selectivity(VariableStatData *vardata, FmgrInfo *opproc,
 129                                           Datum constval, bool varonleft,
 130                                           int min_hist_size, int n_skip,
 131                                           int *hist_size);
 132
 133 extern Pattern_Prefix_Status pattern_fixed_prefix(Const *patt,
 134                                          Pattern_Type ptype,
 135                                          Const **prefix,
 136                                          Const **rest);
 137 extern Const *make_greater_string(const Const *str_const, FmgrInfo *ltproc);
 138
 139 extern Datum eqsel(PG_FUNCTION_ARGS);
 140 extern Datum neqsel(PG_FUNCTION_ARGS);
 141 extern Datum scalarltsel(PG_FUNCTION_ARGS);
 142 extern Datum scalargtsel(PG_FUNCTION_ARGS);
 143 extern Datum regexeqsel(PG_FUNCTION_ARGS);
 144 extern Datum icregexeqsel(PG_FUNCTION_ARGS);
 145 extern Datum likesel(PG_FUNCTION_ARGS);
 146 extern Datum iclikesel(PG_FUNCTION_ARGS);
 147 extern Datum regexnesel(PG_FUNCTION_ARGS);
 148 extern Datum icregexnesel(PG_FUNCTION_ARGS);
 149 extern Datum nlikesel(PG_FUNCTION_ARGS);
 150 extern Datum icnlikesel(PG_FUNCTION_ARGS);
 151
 152 extern Datum eqjoinsel(PG_FUNCTION_ARGS);
 153 extern Datum neqjoinsel(PG_FUNCTION_ARGS);
 154 extern Datum scalarltjoinsel(PG_FUNCTION_ARGS);
 155 extern Datum scalargtjoinsel(PG_FUNCTION_ARGS);
 156 extern Datum regexeqjoinsel(PG_FUNCTION_ARGS);
 157 extern Datum icregexeqjoinsel(PG_FUNCTION_ARGS);
 158 extern Datum likejoinsel(PG_FUNCTION_ARGS);
 159 extern Datum iclikejoinsel(PG_FUNCTION_ARGS);
 160 extern Datum regexnejoinsel(PG_FUNCTION_ARGS);
 161 extern Datum icregexnejoinsel(PG_FUNCTION_ARGS);
 162 extern Datum nlikejoinsel(PG_FUNCTION_ARGS);
 163 extern Datum icnlikejoinsel(PG_FUNCTION_ARGS);
 164
 165 extern Selectivity booltestsel(PlannerInfo *root, BoolTestType booltesttype,
 166                         Node *arg, int varRelid,
 167                         JoinType jointype, SpecialJoinInfo *sjinfo);
 168 extern Selectivity nulltestsel(PlannerInfo *root, NullTestType nulltesttype,
 169                         Node *arg, int varRelid,
 170                         JoinType jointype, SpecialJoinInfo *sjinfo);
 171 extern Selectivity scalararraysel(PlannerInfo *root,
 172                            ScalarArrayOpExpr *clause,
 173                            bool is_join_clause,
 174                            int varRelid, JoinType jointype, SpecialJoinInfo *sjinfo);
 175 extern int      estimate_array_length(Node *arrayexpr);
 176 extern Selectivity rowcomparesel(PlannerInfo *root,
 177                           RowCompareExpr *clause,
 178                           int varRelid, JoinType jointype, SpecialJoinInfo *sjinfo);
 179
 180 extern void mergejoinscansel(PlannerInfo *root, Node *clause,
 181                                  Oid opfamily, int strategy, bool nulls_first,
 182                                  Selectivity *leftstart, Selectivity *leftend,
 183                                  Selectivity *rightstart, Selectivity *rightend);
 184
 185 extern double estimate_num_groups(PlannerInfo *root, List *groupExprs,
 186                                         double input_rows);
 187
 188 extern Selectivity estimate_hash_bucketsize(PlannerInfo *root, Node *hashkey,
 189                                                  double nbuckets);
 190
 191 extern Datum btcostestimate(PG_FUNCTION_ARGS);
 192 extern Datum hashcostestimate(PG_FUNCTION_ARGS);
 193 extern Datum gistcostestimate(PG_FUNCTION_ARGS);
 194 extern Datum gincostestimate(PG_FUNCTION_ARGS);
 195
 196 #endif   /* SELFUNCS_H */