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Add KNNGIST support to contrib/btree_gist.

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This extends GiST's support for nearest-neighbor searches to many of the
standard data types.

Teodor Sigaev
This commit is contained in:
Tom Lane
2011-03-02 14:43:24 -05:00
parent 6094c242d1
commit 8436489c81
40 changed files with 1546 additions and 59 deletions
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28
doc/src/sgml/btree-gist.sgml
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@ -8,7 +8,7 @@
</indexterm>
<para>
<filename>btree_gist</> provides sample GiST operator classes that
<filename>btree_gist</> provides GiST index operator classes that
implement B-tree equivalent behavior for the data types
<type>int2</>, <type>int4</>, <type>int8</>, <type>float4</>,
<type>float8</>, <type>numeric</>, <type>timestamp with time zone</>,
@ -23,18 +23,34 @@
In general, these operator classes will not outperform the equivalent
standard B-tree index methods, and they lack one major feature of the
standard B-tree code: the ability to enforce uniqueness. However,
they are useful for GiST testing and as a base for developing other
GiST operator classes.
they provide some other features that are not available with a B-tree
index, as described below. Also, these operator classes are useful
when a multi-column GiST index is needed, wherein some of the columns
are of data types that are only indexable with GiST but other columns
are just simple data types. Lastly, these operator classes are useful for
GiST testing and as a base for developing other GiST operator classes.
</para>
<para>
In addition to the typical btree search operators, btree_gist also
provides search operators for <literal>&lt;&gt;</literal> (<quote>not
In addition to the typical B-tree search operators, <filename>btree_gist</>
also provides index support for <literal>&lt;&gt;</literal> (<quote>not
equals</quote>). This may be useful in combination with an
<link linkend="SQL-CREATETABLE-EXCLUDE">exclusion constraint</link>,
as described below.
</para>
<para>
Also, for data types for which there is a natural distance metric,
<filename>btree_gist</> defines a distance operator <literal>&lt;-&gt;</>,
and provides GiST index support for nearest-neighbor searches using
this operator. Distance operators are provided for
<type>int2</>, <type>int4</>, <type>int8</>, <type>float4</>,
<type>float8</>, <type>timestamp with time zone</>,
<type>timestamp without time zone</>,
<type>time without time zone</>, <type>date</>, <type>interval</>,
<type>oid</>, and <type>money</>.
</para>
<sect2>
<title>Example Usage</title>
@ -48,6 +64,8 @@ CREATE TABLE test (a int4);
CREATE INDEX testidx ON test USING gist (a);
-- query
SELECT * FROM test WHERE a &lt; 10;
-- nearest-neighbor search: find the ten entries closest to "42"
SELECT *, a &lt;-&gt; 42 AS dist FROM test ORDER BY a &lt;-&gt; 42 LIMIT 10;
</programlisting>
<para>