From: Jeff Davis <jdavis@postgresql.org>
Date: Wed, 15 Jul 2026 19:34:20 +0000 (-0700)
Subject: Fix like_fixed_prefix_ci() selectivity.
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=94e1b104f8db88837e5ef13a6692dad746e3690f;p=thirdparty%2Fpostgresql.git

Fix like_fixed_prefix_ci() selectivity.

A wrong calculation introduced by 9c8de15969 could cause trailing
characters from the prefix to be passed to like_selectivity() rather
than just the "rest".

Discussion: https://postgr.es/m/c7334a7a44243d2e4ec5e83747589908b3787491.camel@j-davis.com
Backpatch-through: 19
---

diff --git a/src/backend/utils/adt/like_support.c b/src/backend/utils/adt/like_support.c
index 4c8db9147ee..e354360a8e6 100644
--- a/src/backend/utils/adt/like_support.c
+++ b/src/backend/utils/adt/like_support.c
@@ -1150,12 +1150,12 @@ like_fixed_prefix_ci(Const *patt_const, Oid collation, Const **prefix_const,
 
 	if (rest_selec != NULL)
 	{
-		int			wrestlen = wpattlen - wmatch_pos;
+		int			wrestlen = wpattlen - wpos;
 		char	   *rest;
 		int			rest_mblen;
 
 		rest = palloc(pg_database_encoding_max_length() * wrestlen + 1);
-		rest_mblen = pg_wchar2mb_with_len(&wpatt[wmatch_pos], rest, wrestlen);
+		rest_mblen = pg_wchar2mb_with_len(&wpatt[wpos], rest, wrestlen);
 
 		*rest_selec = like_selectivity(rest, rest_mblen, true);
 		pfree(rest);