From 1fe9e3822c4e574aa526b99af723e61e03f36d4f Mon Sep 17 00:00:00 2001
From: Alexander Korotkov <akorotkov@postgresql.org>
Date: Tue, 29 Jul 2025 10:41:13 +0300
Subject: [PATCH] Clarify documentation for the initcap function

This commit documents differences in the definition of word separators for
the initcap function between libc and ICU locale providers.
Backpatch to all supported branches.

Discussion: https://postgr.es/m/804cc10ef95d4d3b298e76b181fd9437%40postgrespro.ru
Author: Oleg Tselebrovskiy <o.tselebrovskiy@postgrespro.ru>
Backpatch-through: 13
---
 doc/src/sgml/func.sgml | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index 479b66b0a5b..05e6d78ad6a 100644
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -3148,8 +3148,11 @@ SELECT NOT(ROW(table.*) IS NOT NULL) FROM TABLE; -- detect at least one null in
        </para>
        <para>
         Converts the first letter of each word to upper case and the
-        rest to lower case. Words are sequences of alphanumeric
-        characters separated by non-alphanumeric characters.
+        rest to lower case. When using the <literal>libc</literal> locale
+        provider, words are sequences of alphanumeric characters separated
+        by non-alphanumeric characters; when using the ICU locale provider,
+        words are separated according to
+        <ulink url="https://www.unicode.org/reports/tr29/#Word_Boundaries">Unicode Standard Annex #29</ulink>.
        </para>
        <para>
         <literal>initcap('hi THOMAS')</literal>
-- 
2.47.2