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selfuncs.h
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1 /*-------------------------------------------------------------------------
2  *
3  * selfuncs.h
4  * Selectivity functions for standard operators, and assorted
5  * infrastructure for selectivity and cost estimation.
6  *
7  *
8  * Portions Copyright (c) 1996-2017, PostgreSQL Global Development Group
9  * Portions Copyright (c) 1994, Regents of the University of California
10  *
11  * src/include/utils/selfuncs.h
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; /* matches unique index or DISTINCT clause */
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 {
91 } Pattern_Type;
92 
93 typedef enum
94 {
97 
98 /*
99  * deconstruct_indexquals is a simple function to examine the indexquals
100  * attached to a proposed IndexPath. It returns a list of IndexQualInfo
101  * structs, one per qual expression.
102  */
103 typedef struct
104 {
105  RestrictInfo *rinfo; /* the indexqual itself */
106  int indexcol; /* zero-based index column number */
107  bool varonleft; /* true if index column is on left of qual */
108  Oid clause_op; /* qual's operator OID, if relevant */
109  Node *other_operand; /* non-index operand of qual's operator */
110 } IndexQualInfo;
111 
112 /*
113  * genericcostestimate is a general-purpose estimator that can be used for
114  * most index types. In some cases we use genericcostestimate as the base
115  * code and then incorporate additional index-type-specific knowledge in
116  * the type-specific calling function. To avoid code duplication, we make
117  * genericcostestimate return a number of intermediate values as well as
118  * its preliminary estimates of the output cost values. The GenericCosts
119  * struct includes all these values.
120  *
121  * Callers should initialize all fields of GenericCosts to zero. In addition,
122  * they can set numIndexTuples to some positive value if they have a better
123  * than default way of estimating the number of leaf index tuples visited.
124  */
125 typedef struct
126 {
127  /* These are the values the cost estimator must return to the planner */
128  Cost indexStartupCost; /* index-related startup cost */
129  Cost indexTotalCost; /* total index-related scan cost */
130  Selectivity indexSelectivity; /* selectivity of index */
131  double indexCorrelation; /* order correlation of index */
132 
133  /* Intermediate values we obtain along the way */
134  double numIndexPages; /* number of leaf pages visited */
135  double numIndexTuples; /* number of leaf tuples visited */
136  double spc_random_page_cost; /* relevant random_page_cost value */
137  double num_sa_scans; /* # indexscans from ScalarArrayOps */
138 } GenericCosts;
139 
140 /* Hooks for plugins to get control when we ask for stats */
142  RangeTblEntry *rte,
143  AttrNumber attnum,
144  VariableStatData *vardata);
147  Oid indexOid,
148  AttrNumber indexattnum,
149  VariableStatData *vardata);
151 
152 /* Functions in selfuncs.c */
153 
154 extern void examine_variable(PlannerInfo *root, Node *node, int varRelid,
155  VariableStatData *vardata);
156 extern bool get_restriction_variable(PlannerInfo *root, List *args,
157  int varRelid,
158  VariableStatData *vardata, Node **other,
159  bool *varonleft);
160 extern void get_join_variables(PlannerInfo *root, List *args,
161  SpecialJoinInfo *sjinfo,
162  VariableStatData *vardata1,
163  VariableStatData *vardata2,
164  bool *join_is_reversed);
165 extern double get_variable_numdistinct(VariableStatData *vardata,
166  bool *isdefault);
167 extern double mcv_selectivity(VariableStatData *vardata, FmgrInfo *opproc,
168  Datum constval, bool varonleft,
169  double *sumcommonp);
170 extern double histogram_selectivity(VariableStatData *vardata, FmgrInfo *opproc,
171  Datum constval, bool varonleft,
172  int min_hist_size, int n_skip,
173  int *hist_size);
174 
176  Pattern_Type ptype,
177  Oid collation,
178  Const **prefix,
179  Selectivity *rest_selec);
180 extern Const *make_greater_string(const Const *str_const, FmgrInfo *ltproc,
181  Oid collation);
182 
183 extern Selectivity boolvarsel(PlannerInfo *root, Node *arg, int varRelid);
184 extern Selectivity booltestsel(PlannerInfo *root, BoolTestType booltesttype,
185  Node *arg, int varRelid,
186  JoinType jointype, SpecialJoinInfo *sjinfo);
187 extern Selectivity nulltestsel(PlannerInfo *root, NullTestType nulltesttype,
188  Node *arg, int varRelid,
189  JoinType jointype, SpecialJoinInfo *sjinfo);
191  ScalarArrayOpExpr *clause,
192  bool is_join_clause,
193  int varRelid, JoinType jointype, SpecialJoinInfo *sjinfo);
194 extern int estimate_array_length(Node *arrayexpr);
196  RowCompareExpr *clause,
197  int varRelid, JoinType jointype, SpecialJoinInfo *sjinfo);
198 
199 extern void mergejoinscansel(PlannerInfo *root, Node *clause,
200  Oid opfamily, int strategy, bool nulls_first,
201  Selectivity *leftstart, Selectivity *leftend,
202  Selectivity *rightstart, Selectivity *rightend);
203 
204 extern double estimate_num_groups(PlannerInfo *root, List *groupExprs,
205  double input_rows, List **pgset);
206 
208  double nbuckets);
209 
210 extern List *deconstruct_indexquals(IndexPath *path);
211 extern void genericcostestimate(PlannerInfo *root, IndexPath *path,
212  double loop_count,
213  List *qinfos,
214  GenericCosts *costs);
215 
216 /* Functions in array_selfuncs.c */
217 
219  Node *leftop, Node *rightop,
220  Oid elemtype, bool isEquality, bool useOr,
221  int varRelid);
222 
223 #endif /* SELFUNCS_H */
Selectivity indexSelectivity
Definition: selfuncs.h:130
Definition: fmgr.h:53
Selectivity estimate_hash_bucketsize(PlannerInfo *root, Node *hashkey, double nbuckets)
Definition: selfuncs.c:3596
HeapTuple statsTuple
Definition: selfuncs.h:71
Selectivity rowcomparesel(PlannerInfo *root, RowCompareExpr *clause, int varRelid, JoinType jointype, SpecialJoinInfo *sjinfo)
Definition: selfuncs.c:2121
PGDLLIMPORT get_relation_stats_hook_type get_relation_stats_hook
Definition: selfuncs.c:151
BoolTestType
Definition: primnodes.h:1193
double estimate_num_groups(PlannerInfo *root, List *groupExprs, double input_rows, List **pgset)
Definition: selfuncs.c:3277
RelOptInfo * rel
Definition: selfuncs.h:70
bool(* get_index_stats_hook_type)(PlannerInfo *root, Oid indexOid, AttrNumber indexattnum, VariableStatData *vardata)
Definition: selfuncs.h:146
Pattern_Type
Definition: selfuncs.h:87
Definition: nodes.h:522
Selectivity scalararraysel(PlannerInfo *root, ScalarArrayOpExpr *clause, bool is_join_clause, int varRelid, JoinType jointype, SpecialJoinInfo *sjinfo)
Definition: selfuncs.c:1764
double Selectivity
Definition: nodes.h:645
NullTestType
Definition: primnodes.h:1170
unsigned int Oid
Definition: postgres_ext.h:31
List * deconstruct_indexquals(IndexPath *path)
Definition: selfuncs.c:6232
int32 atttypmod
Definition: selfuncs.h:76
RestrictInfo * rinfo
Definition: selfuncs.h:105
void examine_variable(PlannerInfo *root, Node *node, int varRelid, VariableStatData *vardata)
Definition: selfuncs.c:4560
#define PGDLLIMPORT
Definition: c.h:1063
char bool
Definition: c.h:202
signed int int32
Definition: c.h:256
JoinType
Definition: nodes.h:679
Selectivity boolvarsel(PlannerInfo *root, Node *arg, int varRelid)
Definition: selfuncs.c:1460
Selectivity scalararraysel_containment(PlannerInfo *root, Node *leftop, Node *rightop, Oid elemtype, bool isEquality, bool useOr, int varRelid)
bool get_restriction_variable(PlannerInfo *root, List *args, int varRelid, VariableStatData *vardata, Node **other, bool *varonleft)
Definition: selfuncs.c:4441
double num_sa_scans
Definition: selfuncs.h:137
Selectivity nulltestsel(PlannerInfo *root, NullTestType nulltesttype, Node *arg, int varRelid, JoinType jointype, SpecialJoinInfo *sjinfo)
Definition: selfuncs.c:1664
double histogram_selectivity(VariableStatData *vardata, FmgrInfo *opproc, Datum constval, bool varonleft, int min_hist_size, int n_skip, int *hist_size)
Definition: selfuncs.c:689
int estimate_array_length(Node *arrayexpr)
Definition: selfuncs.c:2083
Cost indexTotalCost
Definition: selfuncs.h:129
Const * make_greater_string(const Const *str_const, FmgrInfo *ltproc, Oid collation)
Definition: selfuncs.c:6006
double indexCorrelation
Definition: selfuncs.h:131
double mcv_selectivity(VariableStatData *vardata, FmgrInfo *opproc, Datum constval, bool varonleft, double *sumcommonp)
Definition: selfuncs.c:611
uintptr_t Datum
Definition: postgres.h:372
double get_variable_numdistinct(VariableStatData *vardata, bool *isdefault)
Definition: selfuncs.c:4904
bool varonleft
Definition: selfuncs.h:107
double spc_random_page_cost
Definition: selfuncs.h:136
Pattern_Prefix_Status pattern_fixed_prefix(Const *patt, Pattern_Type ptype, Oid collation, Const **prefix, Selectivity *rest_selec)
Definition: selfuncs.c:5641
struct VariableStatData VariableStatData
PGDLLIMPORT get_index_stats_hook_type get_index_stats_hook
Definition: selfuncs.c:152
double numIndexTuples
Definition: selfuncs.h:135
Selectivity booltestsel(PlannerInfo *root, BoolTestType booltesttype, Node *arg, int varRelid, JoinType jointype, SpecialJoinInfo *sjinfo)
Definition: selfuncs.c:1499
bool(* get_relation_stats_hook_type)(PlannerInfo *root, RangeTblEntry *rte, AttrNumber attnum, VariableStatData *vardata)
Definition: selfuncs.h:141
Cost indexStartupCost
Definition: selfuncs.h:128
void genericcostestimate(PlannerInfo *root, IndexPath *path, double loop_count, List *qinfos, GenericCosts *costs)
Definition: selfuncs.c:6381
Node * other_operand
Definition: selfuncs.h:109
void * arg
void mergejoinscansel(PlannerInfo *root, Node *clause, Oid opfamily, int strategy, bool nulls_first, Selectivity *leftstart, Selectivity *leftend, Selectivity *rightstart, Selectivity *rightend)
Definition: selfuncs.c:2853
void(* freefunc)(HeapTuple tuple)
Definition: selfuncs.h:73
Definition: pg_list.h:45
int16 AttrNumber
Definition: attnum.h:21
double Cost
Definition: nodes.h:646
Pattern_Prefix_Status
Definition: selfuncs.h:93
void get_join_variables(PlannerInfo *root, List *args, SpecialJoinInfo *sjinfo, VariableStatData *vardata1, VariableStatData *vardata2, bool *join_is_reversed)
Definition: selfuncs.c:4501
double numIndexPages
Definition: selfuncs.h:134