From 8ae503a5bee27959bcb063785d3dd25cb4966eca Mon Sep 17 00:00:00 2001
From: Simon Riggs <simon@2ndQuadrant.com>
Date: Wed, 17 Oct 2012 08:35:39 +0100
Subject: [PATCH] Add hash index caution to CREATE INDEX docs

---
 doc/src/sgml/ref/create_index.sgml | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/doc/src/sgml/ref/create_index.sgml b/doc/src/sgml/ref/create_index.sgml
index 5104a656e9..400450460d 100644
--- a/doc/src/sgml/ref/create_index.sgml
+++ b/doc/src/sgml/ref/create_index.sgml
@@ -428,6 +428,18 @@ Indexes:
    they can be useful.
   </para>
 
+  <caution>
+   <para>
+    Hash index operations are not presently WAL-logged,
+    so hash indexes might need to be rebuilt with <command>REINDEX</>
+    after a database crash if there were unwritten changes.
+    Also, changes to hash indexes are not replicated over warm standby
+    replication after the initial base backup, so they
+    give wrong anwers to queries that subsequently use them.
+    For these reasons, hash index use is presently discouraged.
+   </para>
+  </caution>
+
   <para>
    Currently, only the B-tree, GiST and GIN index methods support
    multicolumn indexes. Up to 32 fields can be specified by default.
-- 
2.50.0