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Commitd6061d2

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Fix regex_fixed_prefix() to cope reasonably well with regex patterns of the
form '^(foo)$'. Before, these could never be optimized into indexscans.The recent changes to make psql and pg_dump generate such patterns (for \dcommands and -t and related switches, respectively) therefore representeda big performance hit for people with large pg_class catalogs, as seen inrecent gripe from Erik Jones. While at it, be more paranoid aboutcase-sensitivity checking in multibyte encodings, and fix some othercorner cases in which a regex might be interpreted too liberally.
1 parent9c88830 commitd6061d2

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3 files changed

+105
-46
lines changed

3 files changed

+105
-46
lines changed

‎src/backend/utils/adt/regexp.c‎

Lines changed: 10 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -8,7 +8,7 @@
88
*
99
*
1010
* IDENTIFICATION
11-
* $PostgreSQL: pgsql/src/backend/utils/adt/regexp.c,v 1.66 2006/10/04 00:29:59 momjian Exp $
11+
* $PostgreSQL: pgsql/src/backend/utils/adt/regexp.c,v 1.67 2007/01/03 22:39:26 tgl Exp $
1212
*
1313
*Alistair Crooks added the code for the regex caching
1414
*agc - cached the regular expressions used - there's a good chance
@@ -624,3 +624,12 @@ similar_escape(PG_FUNCTION_ARGS)
624624

625625
PG_RETURN_TEXT_P(result);
626626
}
627+
628+
/*
629+
* report whether regex_flavor is currently BASIC
630+
*/
631+
bool
632+
regex_flavor_is_basic(void)
633+
{
634+
return (regex_flavor==REG_BASIC);
635+
}

‎src/backend/utils/adt/selfuncs.c‎

Lines changed: 93 additions & 44 deletions
Original file line numberDiff line numberDiff line change
@@ -15,7 +15,7 @@
1515
*
1616
*
1717
* IDENTIFICATION
18-
* $PostgreSQL: pgsql/src/backend/utils/adt/selfuncs.c,v 1.216 2006/12/23 00:43:11 tgl Exp $
18+
* $PostgreSQL: pgsql/src/backend/utils/adt/selfuncs.c,v 1.217 2007/01/03 22:39:26 tgl Exp $
1919
*
2020
*-------------------------------------------------------------------------
2121
*/
@@ -3805,7 +3805,10 @@ get_variable_maximum(PlannerInfo *root, VariableStatData *vardata,
38053805
* These routines support analysis of LIKE and regular-expression patterns
38063806
* by the planner/optimizer. It's important that they agree with the
38073807
* regular-expression code in backend/regex/ and the LIKE code in
3808-
* backend/utils/adt/like.c.
3808+
* backend/utils/adt/like.c. Also, the computation of the fixed prefix
3809+
* must be conservative: if we report a string longer than the true fixed
3810+
* prefix, the query may produce actually wrong answers, rather than just
3811+
* getting a bad selectivity estimate!
38093812
*
38103813
* Note that the prefix-analysis functions are called from
38113814
* backend/optimizer/path/indxpath.c as well as from routines in this file.
@@ -3837,6 +3840,7 @@ like_fixed_prefix(Const *patt_const, bool case_insensitive,
38373840
Oidtypeid=patt_const->consttype;
38383841
intpos,
38393842
match_pos;
3843+
boolis_multibyte= (pg_database_encoding_max_length()>1);
38403844

38413845
/* the right-hand const is type text or bytea */
38423846
Assert(typeid==BYTEAOID||typeid==TEXTOID);
@@ -3880,11 +3884,16 @@ like_fixed_prefix(Const *patt_const, bool case_insensitive,
38803884
}
38813885

38823886
/*
3883-
* XXXI suspect isalpha() is not an adequately locale-sensitive test
3884-
*for characters that can vary undercase folding?
3887+
* XXXIn multibyte character sets, we can't trust isalpha, so assume
3888+
*any multibyte char is potentiallycase-varying.
38853889
*/
3886-
if (case_insensitive&&isalpha((unsignedchar)patt[pos]))
3887-
break;
3890+
if (case_insensitive)
3891+
{
3892+
if (is_multibyte&& (unsignedchar)patt[pos] >=0x80)
3893+
break;
3894+
if (isalpha((unsignedchar)patt[pos]))
3895+
break;
3896+
}
38883897

38893898
/*
38903899
* NOTE: this code used to think that %% meant a literal %, but
@@ -3929,11 +3938,13 @@ regex_fixed_prefix(Const *patt_const, bool case_insensitive,
39293938
intpos,
39303939
match_pos,
39313940
prev_pos,
3932-
prev_match_pos,
3933-
paren_depth;
3941+
prev_match_pos;
3942+
boolhave_leading_paren;
39343943
char*patt;
39353944
char*rest;
39363945
Oidtypeid=patt_const->consttype;
3946+
boolis_basic=regex_flavor_is_basic();
3947+
boolis_multibyte= (pg_database_encoding_max_length()>1);
39373948

39383949
/*
39393950
* Should be unnecessary, there are no bytea regex operators defined. As
@@ -3948,8 +3959,19 @@ regex_fixed_prefix(Const *patt_const, bool case_insensitive,
39483959
/* the right-hand const is type text for all of these */
39493960
patt=DatumGetCString(DirectFunctionCall1(textout,patt_const->constvalue));
39503961

3962+
/*
3963+
* Check for ARE director prefix. It's worth our trouble to recognize
3964+
* this because similar_escape() uses it.
3965+
*/
3966+
pos=0;
3967+
if (strncmp(patt,"***:",4)==0)
3968+
{
3969+
pos=4;
3970+
is_basic= false;
3971+
}
3972+
39513973
/* Pattern must be anchored left */
3952-
if (patt[0]!='^')
3974+
if (patt[pos]!='^')
39533975
{
39543976
rest=patt;
39553977

@@ -3958,72 +3980,86 @@ regex_fixed_prefix(Const *patt_const, bool case_insensitive,
39583980

39593981
returnPattern_Prefix_None;
39603982
}
3983+
pos++;
39613984

39623985
/*
3963-
* If unquoted | is present at paren level 0 in pattern, then there are
3964-
* multiple alternatives for the start of the string.
3986+
* If '|' is present in pattern, then there may be multiple alternatives
3987+
* for the start of the string. (There are cases where this isn't so,
3988+
* for instance if the '|' is inside parens, but detecting that reliably
3989+
* is too hard.)
39653990
*/
3966-
paren_depth=0;
3967-
for (pos=1;patt[pos];pos++)
3991+
if (strchr(patt+pos,'|')!=NULL)
39683992
{
3969-
if (patt[pos]=='|'&&paren_depth==0)
3970-
{
3971-
rest=patt;
3993+
rest=patt;
39723994

3973-
*prefix_const=NULL;
3974-
*rest_const=string_to_const(rest,typeid);
3995+
*prefix_const=NULL;
3996+
*rest_const=string_to_const(rest,typeid);
39753997

3976-
returnPattern_Prefix_None;
3977-
}
3978-
elseif (patt[pos]=='(')
3979-
paren_depth++;
3980-
elseif (patt[pos]==')'&&paren_depth>0)
3981-
paren_depth--;
3982-
elseif (patt[pos]=='\\')
3983-
{
3984-
/* backslash quotes the next character */
3985-
pos++;
3986-
if (patt[pos]=='\0')
3987-
break;
3988-
}
3998+
returnPattern_Prefix_None;
39893999
}
39904000

39914001
/* OK, allocate space for pattern */
39924002
match=palloc(strlen(patt)+1);
39934003
prev_match_pos=match_pos=0;
39944004

3995-
/* note start at pos 1 to skip leading ^ */
3996-
for (prev_pos=pos=1;patt[pos];)
4005+
/*
4006+
* We special-case the syntax '^(...)$' because psql uses it. But beware:
4007+
* in BRE mode these parentheses are just ordinary characters. Also,
4008+
* sequences beginning "(?" are not what they seem, unless they're "(?:".
4009+
* (We should recognize that, too, because of similar_escape().)
4010+
*
4011+
* Note: it's a bit bogus to be depending on the current regex_flavor
4012+
* setting here, because the setting could change before the pattern is
4013+
* used. We minimize the risk by trusting the flavor as little as we can,
4014+
* but perhaps it would be a good idea to get rid of the "basic" setting.
4015+
*/
4016+
have_leading_paren= false;
4017+
if (patt[pos]=='('&& !is_basic&&
4018+
(patt[pos+1]!='?'||patt[pos+2]==':'))
4019+
{
4020+
have_leading_paren= true;
4021+
pos+= (patt[pos+1]!='?' ?1 :3);
4022+
}
4023+
4024+
/* Scan remainder of pattern */
4025+
prev_pos=pos;
4026+
while (patt[pos])
39974027
{
39984028
intlen;
39994029

40004030
/*
40014031
* Check for characters that indicate multiple possible matches here.
4002-
* XXX I suspect isalpha() is not an adequately locale-sensitive test
4003-
* for characters that can vary under case folding?
4032+
* Also, drop out at ')' or '$' so the termination test works right.
40044033
*/
40054034
if (patt[pos]=='.'||
40064035
patt[pos]=='('||
4036+
patt[pos]==')'||
40074037
patt[pos]=='['||
4008-
patt[pos]=='$'||
4009-
(case_insensitive&&isalpha((unsignedchar)patt[pos])))
4038+
patt[pos]=='^'||
4039+
patt[pos]=='$')
40104040
break;
40114041

40124042
/*
4013-
* In AREs, backslash followed by alphanumeric is an escape, not a
4014-
* quoted character. Must treat it as having multiple possible
4015-
* matches.
4043+
* XXX In multibyte character sets, we can't trust isalpha, so assume
4044+
* any multibyte char is potentially case-varying.
40164045
*/
4017-
if (patt[pos]=='\\'&&isalnum((unsignedchar)patt[pos+1]))
4018-
break;
4046+
if (case_insensitive)
4047+
{
4048+
if (is_multibyte&& (unsignedchar)patt[pos] >=0x80)
4049+
break;
4050+
if (isalpha((unsignedchar)patt[pos]))
4051+
break;
4052+
}
40194053

40204054
/*
40214055
* Check for quantifiers. Except for +, this means the preceding
40224056
* character is optional, so we must remove it from the prefix too!
4057+
* Note: in BREs, \{ is a quantifier.
40234058
*/
40244059
if (patt[pos]=='*'||
40254060
patt[pos]=='?'||
4026-
patt[pos]=='{')
4061+
patt[pos]=='{'||
4062+
(patt[pos]=='\\'&&patt[pos+1]=='{'))
40274063
{
40284064
match_pos=prev_match_pos;
40294065
pos=prev_pos;
@@ -4034,9 +4070,19 @@ regex_fixed_prefix(Const *patt_const, bool case_insensitive,
40344070
pos=prev_pos;
40354071
break;
40364072
}
4073+
4074+
/*
4075+
* Normally, backslash quotes the next character. But in AREs,
4076+
* backslash followed by alphanumeric is an escape, not a quoted
4077+
* character. Must treat it as having multiple possible matches.
4078+
* In BREs, \( is a parenthesis, so don't trust that either.
4079+
* Note: since only ASCII alphanumerics are escapes, we don't have
4080+
* to be paranoid about multibyte here.
4081+
*/
40374082
if (patt[pos]=='\\')
40384083
{
4039-
/* backslash quotes the next character */
4084+
if (isalnum((unsignedchar)patt[pos+1])||patt[pos+1]=='(')
4085+
break;
40404086
pos++;
40414087
if (patt[pos]=='\0')
40424088
break;
@@ -4054,6 +4100,9 @@ regex_fixed_prefix(Const *patt_const, bool case_insensitive,
40544100
match[match_pos]='\0';
40554101
rest=&patt[pos];
40564102

4103+
if (have_leading_paren&&patt[pos]==')')
4104+
pos++;
4105+
40574106
if (patt[pos]=='$'&&patt[pos+1]=='\0')
40584107
{
40594108
rest=&patt[pos+1];

‎src/include/utils/builtins.h‎

Lines changed: 2 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -7,7 +7,7 @@
77
* Portions Copyright (c) 1996-2006, PostgreSQL Global Development Group
88
* Portions Copyright (c) 1994, Regents of the University of California
99
*
10-
* $PostgreSQL: pgsql/src/include/utils/builtins.h,v 1.283 2006/12/30 21:21:55 tgl Exp $
10+
* $PostgreSQL: pgsql/src/include/utils/builtins.h,v 1.284 2007/01/03 22:39:26 tgl Exp $
1111
*
1212
*-------------------------------------------------------------------------
1313
*/
@@ -477,6 +477,7 @@ extern Datum textregexsubstr(PG_FUNCTION_ARGS);
477477
externDatumtextregexreplace_noopt(PG_FUNCTION_ARGS);
478478
externDatumtextregexreplace(PG_FUNCTION_ARGS);
479479
externDatumsimilar_escape(PG_FUNCTION_ARGS);
480+
externboolregex_flavor_is_basic(void);
480481

481482
/* regproc.c */
482483
externDatumregprocin(PG_FUNCTION_ARGS);

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