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Fix LIKE matching with nondeterministic collations and backslashes.

Browse source 
Commit 85b7efa1c added support for LIKE with nondeterministic
collations, but it included a bug in the de-escaping logic for
literal pattern substrings.  That unconditionally skipped all
backslashes, but when it encounters '\\' it should emit the second
backslash as a de-escaped character.  That led to acting as though
the escaped backslash was not there.

Bug: #19474
Reported-by: Bowen Shi <zxwsbg12138@gmail.com>
Author: Nitin Motiani <nitinmotiani@google.com>
Reviewed-by: Zsolt Parragi <zsolt.parragi@percona.com>
Reviewed-by: Ewan Young <kdbase.hack@gmail.com>
Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Discussion: https://postgr.es/m/19474-5b86a95f3d9a7ecb@postgresql.org
Discussion: https://postgr.es/m/CAH5HC94yU+K8Gcdy12M5BS8gwD_SXLSHzc9k5tNk7JDnpBiFMA@mail.gmail.com
Backpatch-through: 18
This commit is contained in:
Tom Lane 2026-07-06 14:35:21 -04:00
parent 431896a84e
commit d6ffcae32a
3 changed files with 40 additions and 3 deletions
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5
src/backend/utils/adt/like_match.c
View file

@ -257,9 +257,8 @@ MatchText(const char *t, int tlen, const char *p, int plen, pg_locale_t locale)
for (const char *c = p; c < p1; c++)
{
if (*c == '\\')
;
else
*(b++) = *c;
c++; /* we already checked this isn't the end */
*(b++) = *c;
}
subpat = buf;

31
src/test/regress/expected/collate.icu.utf8.out
View file

@ -3006,6 +3006,37 @@ SELECT U&'\0061\0308bc' LIKE U&'_\00e4bc' COLLATE ignore_accents;
-- escape character at end of pattern
SELECT 'foox' LIKE 'foo\' COLLATE ignore_accents;
ERROR: LIKE pattern must not end with escape character
-- literal backslash with nondeterministic collation (bug #19474)
SELECT 'back\slash' COLLATE ignore_accents LIKE 'back\slash%' ESCAPE '#';
?column?
----------
t
(1 row)
SELECT 'aäb' COLLATE ignore_accents LIKE 'a#äb' ESCAPE '#' AS multibyte_escape;
multibyte_escape
------------------
t
(1 row)
SELECT 'a\äb' COLLATE ignore_accents LIKE 'a\äb%' ESCAPE '#' AS backslash_multibyte;
backslash_multibyte
---------------------
t
(1 row)
SELECT 'a\b%c' COLLATE ignore_accents LIKE 'a#\b#%%c' ESCAPE '#' AS mixed_escapes;
mixed_escapes
---------------
t
(1 row)
SELECT 'backslash' COLLATE ignore_accents LIKE 'back\\slash%';
?column?
----------
f
(1 row)
-- foreign keys (mixing different nondeterministic collations not allowed)
CREATE TABLE test10pk (x text COLLATE case_sensitive PRIMARY KEY);
CREATE TABLE test10fk (x text COLLATE case_insensitive REFERENCES test10pk (x) ON UPDATE CASCADE ON DELETE CASCADE); -- error

7
src/test/regress/sql/collate.icu.utf8.sql
View file

@ -1083,6 +1083,13 @@ SELECT U&'\0061\0308bc' LIKE U&'_\00e4bc' COLLATE ignore_accents;
-- escape character at end of pattern
SELECT 'foox' LIKE 'foo\' COLLATE ignore_accents;
-- literal backslash with nondeterministic collation (bug #19474)
SELECT 'back\slash' COLLATE ignore_accents LIKE 'back\slash%' ESCAPE '#';
SELECT 'aäb' COLLATE ignore_accents LIKE 'a#äb' ESCAPE '#' AS multibyte_escape;
SELECT 'a\äb' COLLATE ignore_accents LIKE 'a\äb%' ESCAPE '#' AS backslash_multibyte;
SELECT 'a\b%c' COLLATE ignore_accents LIKE 'a#\b#%%c' ESCAPE '#' AS mixed_escapes;
SELECT 'backslash' COLLATE ignore_accents LIKE 'back\\slash%';
-- foreign keys (mixing different nondeterministic collations not allowed)
CREATE TABLE test10pk (x text COLLATE case_sensitive PRIMARY KEY);
CREATE TABLE test10fk (x text COLLATE case_insensitive REFERENCES test10pk (x) ON UPDATE CASCADE ON DELETE CASCADE); -- error