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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
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20
src/backend/utils/adt/varchar.c
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@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/utils/adt/varchar.c,v 1.113 2005/10/15 02:49:30 momjian Exp $
* $PostgreSQL: pgsql/src/backend/utils/adt/varchar.c,v 1.114 2005/12/22 22:50:00 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -614,11 +614,14 @@ bpchareq(PG_FUNCTION_ARGS)
len1 = bcTruelen(arg1);
len2 = bcTruelen(arg2);
/* 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 (len1 != len2)
result = false;
else
result = (varstr_cmp(VARDATA(arg1), len1, VARDATA(arg2), len2) == 0);
result = (strncmp(VARDATA(arg1), VARDATA(arg2), len1) == 0);
PG_FREE_IF_COPY(arg1, 0);
PG_FREE_IF_COPY(arg2, 1);
@ -638,11 +641,14 @@ bpcharne(PG_FUNCTION_ARGS)
len1 = bcTruelen(arg1);
len2 = bcTruelen(arg2);
/* 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 (len1 != len2)
result = true;
else
result = (varstr_cmp(VARDATA(arg1), len1, VARDATA(arg2), len2) != 0);
result = (strncmp(VARDATA(arg1), VARDATA(arg2), len1) != 0);
PG_FREE_IF_COPY(arg1, 0);
PG_FREE_IF_COPY(arg2, 1);
@ -789,7 +795,9 @@ bpchar_smaller(PG_FUNCTION_ARGS)
* bpchar needs a specialized hash function because we want to ignore
* trailing blanks in comparisons.
*
* XXX is there any need for locale-specific behavior here?
* Note: currently there is no need for locale-specific behavior here,
* but if we ever change the semantics of bpchar comparison to trust
* strcoll() completely, we'd need to do something different in non-C locales.
*/
Datum
hashbpchar(PG_FUNCTION_ARGS)