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Adjust string comparison so that only bitwise-equal strings are considered

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equal: if strcoll claims two strings are equal, check it with strcmp, and
sort according to strcmp if not identical.  This fixes inconsistent
behavior under glibc's hu_HU locale, and probably under some other locales
as well.  Also, take advantage of the now-well-defined behavior to speed up
texteq, textne, bpchareq, bpcharne: they may as well just do a bitwise
comparison and not bother with strcoll at all.

NOTE: affected databases may need to REINDEX indexes on text columns to be
sure they are self-consistent.
This commit is contained in:
Tom Lane
2005-12-22 22:50:00 +00:00
parent 7b53b45a64
commit 656beff590
3 changed files with 40 additions and 15 deletions
src/backend
access
hash
hashfunc.c
utils
adt
varchar.cvarlena.c

27
src/backend/utils/adt/varlena.c

@@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/utils/adt/varlena.c,v 1.141 2005/11/22 18:17:23 momjian Exp $
* $PostgreSQL: pgsql/src/backend/utils/adt/varlena.c,v 1.142 2005/12/22 22:50:00 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -938,6 +938,15 @@ varstr_cmp(char *arg1, int len1, char *arg2, int len2)
result = strcoll(a1p, a2p);
/*
* In some locales strcoll() can claim that nonidentical strings are
* equal. Believing that would be bad news for a number of reasons,
* so we follow Perl's lead and sort "equal" strings according to
* strcmp().
*/
if (result == 0)
result = strcmp(a1p, a2p);
if (a1p != a1buf)
pfree(a1p);
if (a2p != a2buf)
@@ -984,11 +993,15 @@ texteq(PG_FUNCTION_ARGS)
text *arg2 = PG_GETARG_TEXT_P(1);
bool result;
/* fast path for different-length inputs */
/*
* Since we only care about equality or not-equality, we can avoid all
* the expense of strcoll() here, and just do bitwise comparison.
*/
if (VARSIZE(arg1) != VARSIZE(arg2))
result = false;
else
result = (text_cmp(arg1, arg2) == 0);
result = (strncmp(VARDATA(arg1), VARDATA(arg2),
VARSIZE(arg1) - VARHDRSZ) == 0);
PG_FREE_IF_COPY(arg1, 0);
PG_FREE_IF_COPY(arg2, 1);
@@ -1003,11 +1016,15 @@ textne(PG_FUNCTION_ARGS)
text *arg2 = PG_GETARG_TEXT_P(1);
bool result;
/* fast path for different-length inputs */
/*
* Since we only care about equality or not-equality, we can avoid all
* the expense of strcoll() here, and just do bitwise comparison.
*/
if (VARSIZE(arg1) != VARSIZE(arg2))
result = true;
else
result = (text_cmp(arg1, arg2) != 0);
result = (strncmp(VARDATA(arg1), VARDATA(arg2),
VARSIZE(arg1) - VARHDRSZ) != 0);
PG_FREE_IF_COPY(arg1, 0);
PG_FREE_IF_COPY(arg2, 1);