From: Laurenz Albe <laurenz.albe@cybertec.at>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Heikki Linnakangas <hlinnaka@iki.fi>
Cc: adam.warland@infor.com
Cc: pgsql-bugs@lists.postgresql.org
Subject: Re: BUG #19341: REPLACE() fails to match final character when using nondeterministic ICU collation
Date: Tue, 02 Dec 2025 18:51:14 +0100
Message-ID: <464a14fcbee9567ace136716714b8c18f9bd87fb.camel@cybertec.at> (raw)
In-Reply-To: <375807.1764696352@sss.pgh.pa.us>
References: <19341-1d9a22915edfec58@postgresql.org>
<60b467ac47d5c6bbb9c21c3bdfecce8e5de60cda.camel@cybertec.at>
<6935ea1e-cfb1-400b-9057-3d43b55d621a@iki.fi>
<9f47c6b24d6cf59002603caf19b8b3f4854176be.camel@cybertec.at>
<375807.1764696352@sss.pgh.pa.us>
On Tue, 2025-12-02 at 12:25 -0500, Tom Lane wrote:
> Laurenz Albe <laurenz.albe@cybertec.at> writes:
> > > > for (const char *test_end = hptr; test_end <= haystack_end; test_end += pg_mblen(test_end))
>
> > During the last iteration of the loop, "test_end" will be equal to "haystack_end",
> > and the loop increment will call "pg_mblen(test_end)".
>
> Right, clearly unsafe (and I bet valgrind would complain about it).
> You need to rearrange the loop logic so that we won't attempt to
> increment test_end that last time through. Perhaps a for-loop
> isn't the best way to write it.
Right. The attached patch v3 turns it into a while loop to avoid
the problem.
Yours,
Laurenz Albe
Attachments:
[text/x-patch] v3-0001-Fix-greedy-substring-search-for-non-deterministic.patch (3.5K, ../464a14fcbee9567ace136716714b8c18f9bd87fb.camel@cybertec.at/2-v3-0001-Fix-greedy-substring-search-for-non-deterministic.patch)
download | inline diff:
From 41c441a02db341952763d04bb822a634b711c735 Mon Sep 17 00:00:00 2001
From: Laurenz Albe <laurenz.albe@cybertec.at>
Date: Tue, 2 Dec 2025 18:49:11 +0100
Subject: [PATCH v3] Fix greedy substring search for non-deterministic
collations
Due to an off-by-one error, the code failed to find matches at the
end of the haystack.
Author: Laurenz Albe <laurenz.albe@cybertec.at>
Reported-By: Adam Warland <adam.warland@infor.com>
Reviewed-By: Heikki Linnakangas <hlinnaka@iki.fi>
Reviewed-By: Tom Lane <tgl@sss.pgh.pa.us>
Discussion: https://postgr.es/m/19341-1d9a22915edfec58%40postgresql.org
---
src/backend/utils/adt/varlena.c | 9 ++++++++-
src/test/regress/expected/collate.icu.utf8.out | 7 +++++++
src/test/regress/sql/collate.icu.utf8.sql | 3 +++
3 files changed, 18 insertions(+), 1 deletion(-)
diff --git a/src/backend/utils/adt/varlena.c b/src/backend/utils/adt/varlena.cindex 3894457ab40..99d1bf09f20 100644--- a/src/backend/utils/adt/varlena.c+++ b/src/backend/utils/adt/varlena.c@@ -1136,6 +1136,8 @@ text_position_next_internal(char *start_ptr, TextPositionState *state)
hptr = start_ptr;
while (hptr < haystack_end)
{
+ const char *test_end;+
/*
* First check the common case that there is a match in the
* haystack of exactly the length of the needle.
@@ -1149,7 +1151,8 @@ text_position_next_internal(char *start_ptr, TextPositionState *state)
* Else check if any of the possible substrings starting at hptr
* are equal to the needle.
*/
- for (const char *test_end = hptr; test_end < haystack_end; test_end += pg_mblen(test_end))+ test_end = hptr;+ while (test_end <= haystack_end)
{
if (pg_strncoll(hptr, (test_end - hptr), needle, needle_len, state->locale) == 0)
{
@@ -1158,6 +1161,10 @@ text_position_next_internal(char *start_ptr, TextPositionState *state)
if (!state->greedy)
break;
}
++ if (test_end == haystack_end)+ break;+ test_end += pg_mblen(test_end);
}
if (result_hptr)
break;
diff --git a/src/test/regress/expected/collate.icu.utf8.out b/src/test/regress/expected/collate.icu.utf8.outindex b8579a1efc6..0a14c1d93ff 100644--- a/src/test/regress/expected/collate.icu.utf8.out+++ b/src/test/regress/expected/collate.icu.utf8.out@@ -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, 'es');+ replace +---------+ testes+(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;
diff --git a/src/test/regress/sql/collate.icu.utf8.sql b/src/test/regress/sql/collate.icu.utf8.sqlindex 6f5abac0dc0..5e3fef9b381 100644--- a/src/test/regress/sql/collate.icu.utf8.sql+++ b/src/test/regress/sql/collate.icu.utf8.sql@@ -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, 'es');+
-- 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;
--
2.52.0
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To: pgsql-bugs@postgresql.org
Cc: laurenz.albe@cybertec.at, tgl@sss.pgh.pa.us, hlinnaka@iki.fi, adam.warland@infor.com, pgsql-bugs@lists.postgresql.org
Subject: Re: BUG #19341: REPLACE() fails to match final character when using nondeterministic ICU collation
In-Reply-To: <464a14fcbee9567ace136716714b8c18f9bd87fb.camel@cybertec.at>
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