From dd8938e4ba1b1f29d14b3fa2dc76301f42592cad Mon Sep 17 00:00:00 2001
From: Michael Paquier <michael@paquier.xyz>
Date: Wed, 1 Mar 2023 09:05:08 +0900
Subject: [PATCH v3] doc update regarding pg_stat_statements normalization.

It is quite possible that a query text willl not normalize
(replace constants with $1, $2..) when there is a high rate
pgss_hash deallocation. This commit calls this out in docs.
---
 doc/src/sgml/pgstatstatements.sgml | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/doc/src/sgml/pgstatstatements.sgml b/doc/src/sgml/pgstatstatements.sgml
index efc36da602..f1ba78c8cb 100644
--- a/doc/src/sgml/pgstatstatements.sgml
+++ b/doc/src/sgml/pgstatstatements.sgml
@@ -516,6 +516,16 @@
    <structname>pg_stat_statements</structname> entry.
   </para>
 
+  <para>
+   Queries on which normalization can be applied may be observed with constant
+   values in <structname>pg_stat_statements</structname>, especially when there
+   is a high rate of entry deallocations. To reduce the likelihood of this
+   happening, consider increasing <varname>pg_stat_statements.max</varname>.
+   The <structname>pg_stat_statements_info</structname> view, discussed below
+   in <xref linkend="pgstatstatements-pg-stat-statements-info"/>,
+   provides statistics about entry deallocations.
+  </para>
+
   <para>
    In some cases, queries with visibly different texts might get merged into a
    single <structname>pg_stat_statements</structname> entry.  Normally this will happen
-- 
2.39.2