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Mention BRIN as able to do multi-column indexes

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Documentation mentioned B-tree, GiST and GIN as able to do multicolumn
indexes; I failed to add BRIN to the list.

Author: Petr Jediný
Reviewed-By: Fujii Masao, Emre Hasegeli
This commit is contained in:
Alvaro Herrera 2016-03-28 19:11:12 -03:00
parent 1f4e9da624
commit 80b986cf52
1 changed files with 11 additions and 1 deletions
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doc/src/sgml/indices.sgml
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@ -395,7 +395,8 @@ CREATE INDEX test2_mm_idx ON test2 (major, minor);
</para>
<para>
Currently, only the B-tree, GiST and GIN index types support multicolumn
Currently, only the B-tree, GiST, GIN, and BRIN
index types support multicolumn
indexes. Up to 32 columns can be specified. (This limit can be
altered when building <productname>PostgreSQL</productname>; see the
file <filename>pg_config_manual.h</filename>.)
@ -440,6 +441,15 @@ CREATE INDEX test2_mm_idx ON test2 (major, minor);
the query conditions use.
</para>
<para>
A multicolumn BRIN index can be used with query conditions that
involve any subset of the index's columns. Like GIN and unlike B-tree or
GiST, index search effectiveness is the same regardless of which index
column(s) the query conditions use. The only reason to have multiple BRIN
indexes instead of one multicolumn BRIN index on a single table is to have
a different <literal>pages_per_range</literal> storage parameter.
</para>
<para>
Of course, each column must be used with operators appropriate to the index
type; clauses that involve other operators will not be considered.