mirror of
https://github.com/postgres/postgres.git
synced 2025-07-15 19:21:59 +03:00
Add new selectivity estimation functions for pattern-matching operators
(LIKE and regexp matches). These are not yet referenced in pg_operator, so by default the system will continue to use eqsel/neqsel. Also, tweak convert_to_scalar() logic so that common prefixes of strings are stripped off, allowing better accuracy when all strings in a table share a common prefix.
This commit is contained in:
Tom Lane
@ -9,22 +9,20 @@
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*
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*
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* IDENTIFICATION
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* $Header: /cvsroot/pgsql/src/backend/optimizer/path/indxpath.c,v 1.82 2000/04/12 17:15:19 momjian Exp $
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* $Header: /cvsroot/pgsql/src/backend/optimizer/path/indxpath.c,v 1.83 2000/04/16 04:41:01 tgl Exp $
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*
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*-------------------------------------------------------------------------
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*/
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#include <ctype.h>
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#include <math.h>
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#include "postgres.h"
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#include <math.h>
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#include "access/heapam.h"
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#include "access/nbtree.h"
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#include "catalog/catname.h"
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#include "catalog/pg_amop.h"
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#include "catalog/pg_operator.h"
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#include "executor/executor.h"
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#include "mb/pg_wchar.h"
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#include "nodes/makefuncs.h"
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#include "nodes/nodeFuncs.h"
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#include "optimizer/clauses.h"
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@ -46,11 +44,6 @@
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#define is_indexable_operator(clause,opclass,relam,indexkey_on_left) \
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(indexable_operator(clause,opclass,relam,indexkey_on_left) != InvalidOid)
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typedef enum
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{
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Prefix_None, Prefix_Partial, Prefix_Exact
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} Prefix_Status;
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static void match_index_orclauses(RelOptInfo *rel, IndexOptInfo *index,
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List *restrictinfo_list);
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static List *match_index_orclause(RelOptInfo *rel, IndexOptInfo *index,
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@ -92,17 +85,11 @@ static bool function_index_operand(Expr *funcOpnd, RelOptInfo *rel,
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IndexOptInfo *index);
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static bool match_special_index_operator(Expr *clause, Oid opclass, Oid relam,
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bool indexkey_on_left);
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static Prefix_Status like_fixed_prefix(char *patt, char **prefix);
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static Prefix_Status regex_fixed_prefix(char *patt, bool case_insensitive,
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char **prefix);
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static List *prefix_quals(Var *leftop, Oid expr_op,
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char *prefix, Prefix_Status pstatus);
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static char *make_greater_string(const char *str, Oid datatype);
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char *prefix, Pattern_Prefix_Status pstatus);
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static Oid find_operator(const char *opname, Oid datatype);
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static Datum string_to_datum(const char *str, Oid datatype);
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static Const *string_to_const(const char *str, Oid datatype);
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static bool string_lessthan(const char *str1, const char *str2,
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Oid datatype);
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/*
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@ -1644,6 +1631,7 @@ match_special_index_operator(Expr *clause, Oid opclass, Oid relam,
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Datum constvalue;
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char *patt;
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char *prefix;
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char *rest;
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/*
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* Currently, all known special operators require the indexkey on the
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@ -1672,7 +1660,8 @@ match_special_index_operator(Expr *clause, Oid opclass, Oid relam,
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case OID_NAME_LIKE_OP:
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/* the right-hand const is type text for all of these */
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patt = textout((text *) DatumGetPointer(constvalue));
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isIndexable = like_fixed_prefix(patt, &prefix) != Prefix_None;
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isIndexable = pattern_fixed_prefix(patt, Pattern_Type_Like,
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&prefix, &rest) != Pattern_Prefix_None;
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if (prefix)
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pfree(prefix);
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pfree(patt);
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@ -1684,7 +1673,8 @@ match_special_index_operator(Expr *clause, Oid opclass, Oid relam,
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case OID_NAME_REGEXEQ_OP:
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/* the right-hand const is type text for all of these */
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patt = textout((text *) DatumGetPointer(constvalue));
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isIndexable = regex_fixed_prefix(patt, false, &prefix) != Prefix_None;
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isIndexable = pattern_fixed_prefix(patt, Pattern_Type_Regex,
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&prefix, &rest) != Pattern_Prefix_None;
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if (prefix)
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pfree(prefix);
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pfree(patt);
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@ -1696,7 +1686,8 @@ match_special_index_operator(Expr *clause, Oid opclass, Oid relam,
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case OID_NAME_ICREGEXEQ_OP:
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/* the right-hand const is type text for all of these */
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patt = textout((text *) DatumGetPointer(constvalue));
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isIndexable = regex_fixed_prefix(patt, true, &prefix) != Prefix_None;
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isIndexable = pattern_fixed_prefix(patt, Pattern_Type_Regex_IC,
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&prefix, &rest) != Pattern_Prefix_None;
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if (prefix)
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pfree(prefix);
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pfree(patt);
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@ -1776,7 +1767,8 @@ expand_indexqual_conditions(List *indexquals)
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Datum constvalue;
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char *patt;
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char *prefix;
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Prefix_Status pstatus;
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char *rest;
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Pattern_Prefix_Status pstatus;
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switch (expr_op)
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{
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@ -1794,7 +1786,8 @@ expand_indexqual_conditions(List *indexquals)
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/* the right-hand const is type text for all of these */
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constvalue = ((Const *) rightop)->constvalue;
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patt = textout((text *) DatumGetPointer(constvalue));
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pstatus = like_fixed_prefix(patt, &prefix);
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pstatus = pattern_fixed_prefix(patt, Pattern_Type_Like,
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&prefix, &rest);
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resultquals = nconc(resultquals,
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prefix_quals(leftop, expr_op,
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prefix, pstatus));
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@ -1810,7 +1803,8 @@ expand_indexqual_conditions(List *indexquals)
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/* the right-hand const is type text for all of these */
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constvalue = ((Const *) rightop)->constvalue;
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patt = textout((text *) DatumGetPointer(constvalue));
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pstatus = regex_fixed_prefix(patt, false, &prefix);
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pstatus = pattern_fixed_prefix(patt, Pattern_Type_Regex,
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&prefix, &rest);
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resultquals = nconc(resultquals,
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prefix_quals(leftop, expr_op,
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prefix, pstatus));
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@ -1826,7 +1820,8 @@ expand_indexqual_conditions(List *indexquals)
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/* the right-hand const is type text for all of these */
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constvalue = ((Const *) rightop)->constvalue;
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patt = textout((text *) DatumGetPointer(constvalue));
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pstatus = regex_fixed_prefix(patt, true, &prefix);
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pstatus = pattern_fixed_prefix(patt, Pattern_Type_Regex_IC,
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&prefix, &rest);
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resultquals = nconc(resultquals,
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prefix_quals(leftop, expr_op,
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prefix, pstatus));
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@ -1844,130 +1839,6 @@ expand_indexqual_conditions(List *indexquals)
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return resultquals;
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}
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/*
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* Extract the fixed prefix, if any, for a LIKE pattern.
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* *prefix is set to a palloc'd prefix string,
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* or to NULL if no fixed prefix exists for the pattern.
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* The return value distinguishes no fixed prefix, a partial prefix,
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* or an exact-match-only pattern.
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*/
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static Prefix_Status
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like_fixed_prefix(char *patt, char **prefix)
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{
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char *match;
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int pos,
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match_pos;
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*prefix = match = palloc(strlen(patt) + 1);
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match_pos = 0;
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for (pos = 0; patt[pos]; pos++)
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{
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/* % and _ are wildcard characters in LIKE */
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if (patt[pos] == '%' ||
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patt[pos] == '_')
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break;
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/* Backslash quotes the next character */
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if (patt[pos] == '\\')
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{
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pos++;
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if (patt[pos] == '\0')
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break;
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}
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/*
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* NOTE: this code used to think that %% meant a literal %, but
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* textlike() itself does not think that, and the SQL92 spec
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* doesn't say any such thing either.
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*/
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match[match_pos++] = patt[pos];
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}
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match[match_pos] = '\0';
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/* in LIKE, an empty pattern is an exact match! */
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if (patt[pos] == '\0')
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return Prefix_Exact; /* reached end of pattern, so exact */
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if (match_pos > 0)
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return Prefix_Partial;
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return Prefix_None;
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}
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/*
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* Extract the fixed prefix, if any, for a regex pattern.
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* *prefix is set to a palloc'd prefix string,
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* or to NULL if no fixed prefix exists for the pattern.
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* The return value distinguishes no fixed prefix, a partial prefix,
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* or an exact-match-only pattern.
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*/
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static Prefix_Status
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regex_fixed_prefix(char *patt, bool case_insensitive,
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char **prefix)
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{
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char *match;
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int pos,
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match_pos;
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*prefix = NULL;
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/* Pattern must be anchored left */
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if (patt[0] != '^')
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return Prefix_None;
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/* Cannot optimize if unquoted | { } is present in pattern */
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for (pos = 1; patt[pos]; pos++)
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{
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if (patt[pos] == '|' ||
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patt[pos] == '{' ||
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patt[pos] == '}')
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return Prefix_None;
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if (patt[pos] == '\\')
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{
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pos++;
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if (patt[pos] == '\0')
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break;
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}
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}
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/* OK, allocate space for pattern */
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*prefix = match = palloc(strlen(patt) + 1);
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match_pos = 0;
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/* note start at pos 1 to skip leading ^ */
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for (pos = 1; patt[pos]; pos++)
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{
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if (patt[pos] == '.' ||
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patt[pos] == '?' ||
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patt[pos] == '*' ||
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patt[pos] == '[' ||
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patt[pos] == '$' ||
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/*
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* XXX I suspect isalpha() is not an adequately locale-sensitive
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* test for characters that can vary under case folding?
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*/
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(case_insensitive && isalpha(patt[pos])))
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break;
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if (patt[pos] == '\\')
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{
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pos++;
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if (patt[pos] == '\0')
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break;
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}
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match[match_pos++] = patt[pos];
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}
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match[match_pos] = '\0';
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if (patt[pos] == '$' && patt[pos + 1] == '\0')
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return Prefix_Exact; /* pattern specifies exact match */
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if (match_pos > 0)
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return Prefix_Partial;
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return Prefix_None;
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}
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/*
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* Given a fixed prefix that all the "leftop" values must have,
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* generate suitable indexqual condition(s). expr_op is the original
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@ -1976,7 +1847,7 @@ regex_fixed_prefix(char *patt, bool case_insensitive,
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*/
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static List *
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prefix_quals(Var *leftop, Oid expr_op,
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char *prefix, Prefix_Status pstatus)
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char *prefix, Pattern_Prefix_Status pstatus)
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{
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List *result;
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Oid datatype;
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@ -1986,7 +1857,7 @@ prefix_quals(Var *leftop, Oid expr_op,
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Expr *expr;
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char *greaterstr;
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Assert(pstatus != Prefix_None);
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Assert(pstatus != Pattern_Prefix_None);
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switch (expr_op)
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{
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@ -2022,7 +1893,7 @@ prefix_quals(Var *leftop, Oid expr_op,
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/*
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* If we found an exact-match pattern, generate an "=" indexqual.
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*/
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if (pstatus == Prefix_Exact)
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if (pstatus == Pattern_Prefix_Exact)
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{
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oproid = find_operator("=", datatype);
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if (oproid == InvalidOid)
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@ -2067,68 +1938,6 @@ prefix_quals(Var *leftop, Oid expr_op,
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return result;
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}
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/*
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* Try to generate a string greater than the given string or any string it is
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* a prefix of. If successful, return a palloc'd string; else return NULL.
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*
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* To work correctly in non-ASCII locales with weird collation orders,
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* we cannot simply increment "foo" to "fop" --- we have to check whether
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* we actually produced a string greater than the given one. If not,
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* increment the righthand byte again and repeat. If we max out the righthand
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* byte, truncate off the last character and start incrementing the next.
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* For example, if "z" were the last character in the sort order, then we
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* could produce "foo" as a string greater than "fonz".
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*
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* This could be rather slow in the worst case, but in most cases we won't
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* have to try more than one or two strings before succeeding.
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*
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* XXX in a sufficiently weird locale, this might produce incorrect results?
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* For example, in German I believe "ss" is treated specially --- if we are
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* given "foos" and return "foot", will this actually be greater than "fooss"?
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*/
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static char *
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make_greater_string(const char *str, Oid datatype)
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{
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char *workstr;
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int len;
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/*
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* Make a modifiable copy, which will be our return value if
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* successful
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*/
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workstr = pstrdup((char *) str);
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while ((len = strlen(workstr)) > 0)
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{
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unsigned char *lastchar = (unsigned char *) (workstr + len - 1);
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/*
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* Try to generate a larger string by incrementing the last byte.
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*/
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while (*lastchar < (unsigned char) 255)
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{
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(*lastchar)++;
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if (string_lessthan(str, workstr, datatype))
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return workstr; /* Success! */
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}
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/*
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* Truncate off the last character, which might be more than 1
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* byte in MULTIBYTE case.
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*/
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#ifdef MULTIBYTE
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len = pg_mbcliplen((const unsigned char *) workstr, len, len - 1);
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workstr[len] = '\0';
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#else
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*lastchar = '\0';
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#endif
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}
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/* Failed... */
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pfree(workstr);
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return NULL;
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}
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/*
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* Handy subroutines for match_special_index_operator() and friends.
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*/
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@ -2179,45 +1988,3 @@ string_to_const(const char *str, Oid datatype)
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return makeConst(datatype, ((datatype == NAMEOID) ? NAMEDATALEN : -1),
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conval, false, false, false, false);
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}
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/*
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* Test whether two strings are "<" according to the rules of the given
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* datatype. We do this the hard way, ie, actually calling the type's
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* "<" operator function, to ensure we get the right result...
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*/
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static bool
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string_lessthan(const char *str1, const char *str2, Oid datatype)
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{
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Datum datum1 = string_to_datum(str1, datatype);
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Datum datum2 = string_to_datum(str2, datatype);
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bool result;
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switch (datatype)
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{
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case TEXTOID:
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result = text_lt((text *) datum1, (text *) datum2);
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break;
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case BPCHAROID:
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result = bpcharlt((char *) datum1, (char *) datum2);
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break;
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case VARCHAROID:
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result = varcharlt((char *) datum1, (char *) datum2);
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break;
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case NAMEOID:
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result = namelt((NameData *) datum1, (NameData *) datum2);
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break;
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default:
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elog(ERROR, "string_lessthan: unexpected datatype %u", datatype);
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result = false;
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break;
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}
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pfree(DatumGetPointer(datum1));
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pfree(DatumGetPointer(datum2));
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return result;
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}
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Reference in New Issue
Block a user