From 9f9695a0cde67e76a28cde5e695e88e4b4e29137 Mon Sep 17 00:00:00 2001 From: Simon Riggs Date: Wed, 17 Oct 2012 08:14:29 +0100 Subject: [PATCH] Clarify hash index caution and copy to CREATE INDEX docs --- doc/src/sgml/indices.sgml | 6 ++++-- doc/src/sgml/ref/create_index.sgml | 12 ++++++++++++ 2 files changed, 16 insertions(+), 2 deletions(-) diff --git a/doc/src/sgml/indices.sgml b/doc/src/sgml/indices.sgml index 3a46b96a9d..9eb948d6bc 100644 --- a/doc/src/sgml/indices.sgml +++ b/doc/src/sgml/indices.sgml @@ -196,8 +196,10 @@ CREATE INDEX name ON table Hash index operations are not presently WAL-logged, so hash indexes might need to be rebuilt with REINDEX - after a database crash. They are also not replicated over streaming or - file-based replication. + after a database crash if there were unwritten changes. + Also, changes to hash indexes are not replicated over streaming or + file-based 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. diff --git a/doc/src/sgml/ref/create_index.sgml b/doc/src/sgml/ref/create_index.sgml index 17b433a47e..2403b7642a 100644 --- a/doc/src/sgml/ref/create_index.sgml +++ b/doc/src/sgml/ref/create_index.sgml @@ -466,6 +466,18 @@ Indexes: they can be useful. + + + Hash index operations are not presently WAL-logged, + so hash indexes might need to be rebuilt with REINDEX + after a database crash if there were unwritten changes. + Also, changes to hash indexes are not replicated over streaming or + file-based 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. + + + Currently, only the B-tree, GiST and GIN index methods support multicolumn indexes. Up to 32 fields can be specified by default.