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7300a69950
Introduce a third extended statistic type, supported by the CREATE STATISTICS command - MCV lists, a generalization of the statistic already built and used for individual columns. Compared to the already supported types (n-distinct coefficients and functional dependencies), MCV lists are more complex, include column values and allow estimation of much wider range of common clauses (equality and inequality conditions, IS NULL, IS NOT NULL etc.). Similarly to the other types, a new pseudo-type (pg_mcv_list) is used. Author: Tomas Vondra Reviewed-by: Dean Rasheed, David Rowley, Mark Dilger, Alvaro Herrera Discussion: https://postgr.es/m/dfdac334-9cf2-2597-fb27-f0fb3753f435@2ndquadrant.com
121 lines
4.2 KiB
C
121 lines
4.2 KiB
C
/*-------------------------------------------------------------------------
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*
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* bitmapset.h
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* PostgreSQL generic bitmap set package
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*
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* A bitmap set can represent any set of nonnegative integers, although
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* it is mainly intended for sets where the maximum value is not large,
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* say at most a few hundred. By convention, a NULL pointer is always
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* accepted by all operations to represent the empty set. (But beware
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* that this is not the only representation of the empty set. Use
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* bms_is_empty() in preference to testing for NULL.)
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*
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*
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* Copyright (c) 2003-2019, PostgreSQL Global Development Group
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*
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* src/include/nodes/bitmapset.h
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*
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*-------------------------------------------------------------------------
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*/
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#ifndef BITMAPSET_H
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#define BITMAPSET_H
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/*
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* Forward decl to save including pg_list.h
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*/
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struct List;
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/*
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* Data representation
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*
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* Larger bitmap word sizes generally give better performance, so long as
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* they're not wider than the processor can handle efficiently. We use
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* 64-bit words if pointers are that large, else 32-bit words.
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*/
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#if SIZEOF_VOID_P >= 8
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#define BITS_PER_BITMAPWORD 64
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typedef uint64 bitmapword; /* must be an unsigned type */
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typedef int64 signedbitmapword; /* must be the matching signed type */
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#else
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#define BITS_PER_BITMAPWORD 32
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typedef uint32 bitmapword; /* must be an unsigned type */
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typedef int32 signedbitmapword; /* must be the matching signed type */
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#endif
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typedef struct Bitmapset
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{
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int nwords; /* number of words in array */
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bitmapword words[FLEXIBLE_ARRAY_MEMBER]; /* really [nwords] */
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} Bitmapset;
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/* result of bms_subset_compare */
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typedef enum
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{
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BMS_EQUAL, /* sets are equal */
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BMS_SUBSET1, /* first set is a subset of the second */
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BMS_SUBSET2, /* second set is a subset of the first */
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BMS_DIFFERENT /* neither set is a subset of the other */
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} BMS_Comparison;
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/* result of bms_membership */
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typedef enum
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{
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BMS_EMPTY_SET, /* 0 members */
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BMS_SINGLETON, /* 1 member */
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BMS_MULTIPLE /* >1 member */
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} BMS_Membership;
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/*
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* function prototypes in nodes/bitmapset.c
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*/
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extern Bitmapset *bms_copy(const Bitmapset *a);
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extern bool bms_equal(const Bitmapset *a, const Bitmapset *b);
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extern int bms_compare(const Bitmapset *a, const Bitmapset *b);
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extern Bitmapset *bms_make_singleton(int x);
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extern void bms_free(Bitmapset *a);
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extern Bitmapset *bms_union(const Bitmapset *a, const Bitmapset *b);
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extern Bitmapset *bms_intersect(const Bitmapset *a, const Bitmapset *b);
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extern Bitmapset *bms_difference(const Bitmapset *a, const Bitmapset *b);
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extern bool bms_is_subset(const Bitmapset *a, const Bitmapset *b);
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extern BMS_Comparison bms_subset_compare(const Bitmapset *a, const Bitmapset *b);
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extern bool bms_is_member(int x, const Bitmapset *a);
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extern int bms_member_index(Bitmapset *a, int x);
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extern bool bms_overlap(const Bitmapset *a, const Bitmapset *b);
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extern bool bms_overlap_list(const Bitmapset *a, const struct List *b);
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extern bool bms_nonempty_difference(const Bitmapset *a, const Bitmapset *b);
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extern int bms_singleton_member(const Bitmapset *a);
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extern bool bms_get_singleton_member(const Bitmapset *a, int *member);
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extern int bms_num_members(const Bitmapset *a);
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/* optimized tests when we don't need to know exact membership count: */
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extern BMS_Membership bms_membership(const Bitmapset *a);
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extern bool bms_is_empty(const Bitmapset *a);
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/* these routines recycle (modify or free) their non-const inputs: */
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extern Bitmapset *bms_add_member(Bitmapset *a, int x);
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extern Bitmapset *bms_del_member(Bitmapset *a, int x);
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extern Bitmapset *bms_add_members(Bitmapset *a, const Bitmapset *b);
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extern Bitmapset *bms_add_range(Bitmapset *a, int lower, int upper);
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extern Bitmapset *bms_int_members(Bitmapset *a, const Bitmapset *b);
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extern Bitmapset *bms_del_members(Bitmapset *a, const Bitmapset *b);
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extern Bitmapset *bms_join(Bitmapset *a, Bitmapset *b);
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/* support for iterating through the integer elements of a set: */
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extern int bms_first_member(Bitmapset *a);
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extern int bms_next_member(const Bitmapset *a, int prevbit);
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extern int bms_prev_member(const Bitmapset *a, int prevbit);
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/* support for hashtables using Bitmapsets as keys: */
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extern uint32 bms_hash_value(const Bitmapset *a);
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#endif /* BITMAPSET_H */
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