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Commit965a2a1

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Fix regexp substring matching (substring(string from pattern)) for the corner
case where there is a match to the pattern overall but the user has specifieda parenthesized subexpression and that subexpression hasn't got a match.An example is substring('foo' from 'foo(bar)?'). This should return NULL,since (bar) isn't matched, but it was mistakenly returning the whole-patternmatch instead (ie, 'foo'). Per bug #4044 from Rui Martins.This has been broken since the beginning; patch in all supported versions.The old behavior was sufficiently inconsistent that it's impossible to believeanyone is depending on it.
1 parent8436f9a commit965a2a1

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+33
-25
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1 file changed

+33
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‎src/backend/utils/adt/regexp.c

Lines changed: 33 additions & 25 deletions
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 1.78 2008/01/01 19:45:52 momjian Exp $
11+
* $PostgreSQL: pgsql/src/backend/utils/adt/regexp.c,v 1.79 2008/03/19 02:40:37 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
@@ -576,43 +576,51 @@ textregexsubstr(PG_FUNCTION_ARGS)
576576
{
577577
text*s=PG_GETARG_TEXT_PP(0);
578578
text*p=PG_GETARG_TEXT_PP(1);
579-
boolmatch;
579+
regex_t*re;
580580
regmatch_tpmatch[2];
581+
intso,
582+
eo;
583+
584+
/* Compile RE */
585+
re=RE_compile_and_cache(p,regex_flavor);
581586

582587
/*
583588
* We pass two regmatch_t structs to get info about the overall match and
584589
* the match for the first parenthesized subexpression (if any). If there
585590
* is a parenthesized subexpression, we return what it matched; else
586591
* return what the whole regexp matched.
587592
*/
588-
match=RE_compile_and_execute(p,
589-
VARDATA_ANY(s),
590-
VARSIZE_ANY_EXHDR(s),
591-
regex_flavor,
592-
2,pmatch);
593-
594-
/* match? then return the substring matching the pattern */
595-
if (match)
596-
{
597-
intso,
598-
eo;
593+
if (!RE_execute(re,
594+
VARDATA_ANY(s),VARSIZE_ANY_EXHDR(s),
595+
2,pmatch))
596+
PG_RETURN_NULL();/* definitely no match */
599597

598+
if (re->re_nsub>0)
599+
{
600+
/* has parenthesized subexpressions, use the first one */
600601
so=pmatch[1].rm_so;
601602
eo=pmatch[1].rm_eo;
602-
if (so<0||eo<0)
603-
{
604-
/* no parenthesized subexpression */
605-
so=pmatch[0].rm_so;
606-
eo=pmatch[0].rm_eo;
607-
}
608-
609-
returnDirectFunctionCall3(text_substr,
610-
PointerGetDatum(s),
611-
Int32GetDatum(so+1),
612-
Int32GetDatum(eo-so));
613603
}
604+
else
605+
{
606+
/* no parenthesized subexpression, use whole match */
607+
so=pmatch[0].rm_so;
608+
eo=pmatch[0].rm_eo;
609+
}
610+
611+
/*
612+
* It is possible to have a match to the whole pattern but no match
613+
* for a subexpression; for example 'foo(bar)?' is considered to match
614+
* 'foo' but there is no subexpression match. So this extra test for
615+
* match failure is not redundant.
616+
*/
617+
if (so<0||eo<0)
618+
PG_RETURN_NULL();
614619

615-
PG_RETURN_NULL();
620+
returnDirectFunctionCall3(text_substr,
621+
PointerGetDatum(s),
622+
Int32GetDatum(so+1),
623+
Int32GetDatum(eo-so));
616624
}
617625

618626
/*

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