From 656beff59033ccc5261a615802e1a85da68e8fad Mon Sep 17 00:00:00 2001 From: Tom Lane <tgl@sss.pgh.pa.us> Date: Thu, 22 Dec 2005 22:50:00 +0000 Subject: [PATCH] Adjust string comparison so that only bitwise-equal strings are considered 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. --- src/backend/access/hash/hashfunc.c | 8 ++++---- src/backend/utils/adt/varchar.c | 20 ++++++++++++++------ src/backend/utils/adt/varlena.c | 27 ++++++++++++++++++++++----- 3 files changed, 40 insertions(+), 15 deletions(-) diff --git a/src/backend/access/hash/hashfunc.c b/src/backend/access/hash/hashfunc.c index 2ffca5efe6a..6cf9eb6eee2 100644 --- a/src/backend/access/hash/hashfunc.c +++ b/src/backend/access/hash/hashfunc.c @@ -8,7 +8,7 @@ * * * IDENTIFICATION - * $PostgreSQL: pgsql/src/backend/access/hash/hashfunc.c,v 1.45 2005/10/15 02:49:08 momjian Exp $ + * $PostgreSQL: pgsql/src/backend/access/hash/hashfunc.c,v 1.46 2005/12/22 22:50:00 tgl Exp $ * * NOTES * These functions are stored in pg_amproc. For each operator class @@ -138,9 +138,9 @@ hashtext(PG_FUNCTION_ARGS) Datum result; /* - * Note: this is currently identical in behavior to hashvarlena, but it - * seems likely that we may need to do something different in non-C - * locales. (See also hashbpchar, if so.) + * Note: this is currently identical in behavior to hashvarlena, but + * keep it as a separate function in case we someday want to do something + * different in non-C locales. (See also hashbpchar, if so.) */ result = hash_any((unsigned char *) VARDATA(key), VARSIZE(key) - VARHDRSZ); diff --git a/src/backend/utils/adt/varchar.c b/src/backend/utils/adt/varchar.c index 1377e7cc6d2..8fd46531b84 100644 --- a/src/backend/utils/adt/varchar.c +++ b/src/backend/utils/adt/varchar.c @@ -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) diff --git a/src/backend/utils/adt/varlena.c b/src/backend/utils/adt/varlena.c index 69544ea90f6..20b40fe2e5d 100644 --- a/src/backend/utils/adt/varlena.c +++ b/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); -- GitLab