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| author | Simon Riggs <simon@2ndQuadrant.com> | 2012-10-17 08:14:29 +0100 |
|---|---|---|
| committer | Simon Riggs <simon@2ndQuadrant.com> | 2012-10-17 08:14:29 +0100 |
| commit | 9f9695a0cde67e76a28cde5e695e88e4b4e29137 (patch) | |
| tree | a4cf774fa5986ecfc63a2555645f46f0a9b697df /doc/src | |
| parent | 22cc3b35f4d614aff83606a443da475215c6dd84 (diff) | |
| download | postgresql-9f9695a0cde67e76a28cde5e695e88e4b4e29137.tar.gz postgresql-9f9695a0cde67e76a28cde5e695e88e4b4e29137.zip | |
Clarify hash index caution and copy to CREATE INDEX docs
Diffstat (limited to 'doc/src')
| -rw-r--r-- | doc/src/sgml/indices.sgml | 6 | ||||
| -rw-r--r-- | 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 3a46b96a9d2..9eb948d6bcc 100644 --- a/doc/src/sgml/indices.sgml +++ b/doc/src/sgml/indices.sgml @@ -196,8 +196,10 @@ CREATE INDEX <replaceable>name</replaceable> ON <replaceable>table</replaceable> <para> Hash index operations are not presently WAL-logged, so hash indexes might need to be rebuilt with <command>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. </para> </caution> diff --git a/doc/src/sgml/ref/create_index.sgml b/doc/src/sgml/ref/create_index.sgml index 17b433a47e4..2403b7642a1 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. </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 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. + </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. |