From c6ec56913d933f328f4e54ac1ab7123a02d4bccf Mon Sep 17 00:00:00 2001
From: Nikolay Samokhvalov <samokhvalov@gmail.com>
Date: Tue, 27 Oct 2020 07:01:34 +0000
Subject: [PATCH] Building indexes on expressions requires ANALYZE

It is critically important to run ANALYZE after an index on an
expression is created.
---
 doc/src/sgml/indices.sgml | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/doc/src/sgml/indices.sgml b/doc/src/sgml/indices.sgml
index 671299ff05..bb5d7dfdd5 100644
--- a/doc/src/sgml/indices.sgml
+++ b/doc/src/sgml/indices.sgml
@@ -741,6 +741,15 @@ CREATE INDEX people_names ON people ((first_name || ' ' || last_name));
    query.  Thus, indexes on expressions are useful when retrieval speed
    is more important than insertion and update speed.
   </para>
+
+  <note>
+   <title>Note</title>
+   <para>
+    Once an index on an expression is successfuly created, it is important to
+    run <literal>ANALYZE</literal> on the corresponding table to gather
+    statistics for the expression.
+   </para>
+  </note>
  </sect1>