From d861b9282261b066a1147d920a27527c22dc499d 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 4faa7782dce..332d9175e26 100644
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -3049,8 +3049,11 @@ repeat('Pg', 4) <returnvalue>PgPgPgPg</returnvalue>
        </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>