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Clarify hash index caution and copy to CREATE INDEX docs

This commit is contained in:
Simon Riggs 2012-10-17 08:14:29 +01:00
parent 22cc3b35f4
commit 9f9695a0cd
2 changed files with 16 additions and 2 deletions
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6
doc/src/sgml/indices.sgml
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@ -196,8 +196,10 @@ CREATE INDEX <replaceable>name</replaceable> ON <replaceable>table</replaceable>
<para> <para>
Hash index operations are not presently WAL-logged, Hash index operations are not presently WAL-logged,
so hash indexes might need to be rebuilt with <command>REINDEX</> so hash indexes might need to be rebuilt with <command>REINDEX</>
after a database crash. They are also not replicated over streaming or after a database crash if there were unwritten changes.
file-based replication. 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. For these reasons, hash index use is presently discouraged.
</para> </para>
</caution> </caution>

12
doc/src/sgml/ref/create_index.sgml
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@ -466,6 +466,18 @@ Indexes:
they can be useful. they can be useful.
</para> </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> <para>
Currently, only the B-tree, GiST and GIN index methods support Currently, only the B-tree, GiST and GIN index methods support
multicolumn indexes. Up to 32 fields can be specified by default. multicolumn indexes. Up to 32 fields can be specified by default.