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Fix text substring search for non-deterministic collations.

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Due to an off-by-one error, the code failed to find matches at the
end of the haystack.  Fix by rewriting the loop.

While at it, fix a comment that claimed that the function could find
a zero-length match.  Such a match could send a caller into an endless
loop.  However, zero-length matches only make sense with an empty
search string, and that case is explicitly excluded by all callers.
To make sure it stays that way, add an Assert and a comment.

Bug: #19341
Reported-by: Adam Warland <adam.warland@infor.com>
Author: Laurenz Albe <laurenz.albe@cybertec.at>
Reviewed-by: Heikki Linnakangas <hlinnaka@iki.fi>
Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Discussion: https://postgr.es/m/19341-1d9a22915edfec58@postgresql.org
Backpatch-through: 18
This commit is contained in:
Tom Lane
2025-12-05 20:10:33 -05:00
parent 7c2061bdfb
commit 6dfce8420e
3 changed files with 28 additions and 7 deletions
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7
src/test/regress/expected/collate.icu.utf8.out
View File

@@ -1484,6 +1484,13 @@ SELECT array_sort('{a,B}'::text[] COLLATE "C");
{B,a}
(1 row)
-- test replace() at the end of the string (bug #19341)
SELECT replace('testX' COLLATE case_insensitive, 'x' COLLATE case_insensitive, 'er');
replace
---------
tester
(1 row)
-- test language tags
CREATE COLLATION lt_insensitive (provider = icu, locale = 'en-u-ks-level1', deterministic = false);
SELECT 'aBcD' COLLATE lt_insensitive = 'AbCd' COLLATE lt_insensitive;

3
src/test/regress/sql/collate.icu.utf8.sql
View File

@@ -568,6 +568,9 @@ SELECT 'abc' <= 'ABC' COLLATE case_insensitive, 'abc' >= 'ABC' COLLATE case_inse
SELECT array_sort('{a,B}'::text[] COLLATE case_insensitive);
SELECT array_sort('{a,B}'::text[] COLLATE "C");
-- test replace() at the end of the string (bug #19341)
SELECT replace('testX' COLLATE case_insensitive, 'x' COLLATE case_insensitive, 'er');
-- test language tags
CREATE COLLATION lt_insensitive (provider = icu, locale = 'en-u-ks-level1', deterministic = false);
SELECT 'aBcD' COLLATE lt_insensitive = 'AbCd' COLLATE lt_insensitive;