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<sect1 id="intarray">
<title>intarray</title>
<indexterm zone="intarray">
<primary>intarray</primary>
</indexterm>
<para>
This is an implementation of RD-tree data structure using GiST interface
of PostgreSQL. It has built-in lossy compression.
</para>
<para>
Current implementation provides index support for one-dimensional array of
int4's - gist__int_ops, suitable for small and medium size of arrays (used on
default), and gist__intbig_ops for indexing large arrays (we use superimposed
signature with length of 4096 bits to represent sets).
</para>
<sect2>
<title>Functions</title>
<itemizedlist>
<listitem>
<para>
<literal>int icount(int[])</literal> - the number of elements in intarray
</para>
<programlisting>
test=# select icount('{1,2,3}'::int[]);
icount
--------
3
(1 row)
</programlisting>
</listitem>
<listitem>
<para>
<literal>int[] sort(int[], 'asc' | 'desc')</literal> - sort intarray
</para>
<programlisting>
test=# select sort('{1,2,3}'::int[],'desc');
sort
---------
{3,2,1}
(1 row)
</programlisting>
</listitem>
<listitem>
<para>
<literal>int[] sort(int[])</literal> - sort in ascending order
</para>
</listitem>
<listitem>
<para>
<literal>int[] sort_asc(int[]),sort_desc(int[])</literal> - shortcuts for sort
</para>
</listitem>
<listitem>
<para>
<literal>int[] uniq(int[])</literal> - returns unique elements
</para>
<programlisting>
test=# select uniq(sort('{1,2,3,2,1}'::int[]));
uniq
---------
{1,2,3}
(1 row)
</programlisting>
</listitem>
<listitem>
<para>
<literal>int idx(int[], int item)</literal> - returns index of first
intarray matching element to item, or '0' if matching failed.
</para>
<programlisting>
test=# select idx('{1,2,3,2,1}'::int[],2);
idx
-----
2
(1 row)
</programlisting>
</listitem>
<listitem>
<para>
<literal>int[] subarray(int[],int START [, int LEN])</literal> - returns
part of intarray starting from element number START (from 1) and length LEN.
</para>
<programlisting>
test=# select subarray('{1,2,3,2,1}'::int[],2,3);
subarray
----------
{2,3,2}
(1 row)
</programlisting>
</listitem>
<listitem>
<para>
<literal>int[] intset(int4)</literal> - casting int4 to int[]
</para>
<programlisting>
test=# select intset(1);
intset
--------
{1}
(1 row)
</programlisting>
</listitem>
</itemizedlist>
</sect2>
<sect2>
<title>Operations</title>
<table>
<title>Operations</title>
<tgroup cols="2">
<thead>
<row>
<entry>Operator</entry>
<entry>Description</entry>
</row>
</thead>
<tbody>
<row>
<entry><literal>int[] && int[]</literal></entry>
<entry>overlap - returns TRUE if arrays have at least one common element</entry>
</row>
<row>
<entry><literal>int[] @> int[]</literal></entry>
<entry>contains - returns TRUE if left array contains right array</entry>
</row>
<row>
<entry><literal>int[] <@ int[]</literal></entry>
<entry>contained - returns TRUE if left array is contained in right array</entry>
</row>
<row>
<entry><literal># int[]</literal></entry>
<entry>returns the number of elements in array</entry>
</row>
<row>
<entry><literal>int[] + int</literal></entry>
<entry>push element to array ( add to end of array)</entry>
</row>
<row>
<entry><literal>int[] + int[] </literal></entry>
<entry>merge of arrays (right array added to the end of left one)</entry>
</row>
<row>
<entry><literal>int[] - int</literal></entry>
<entry>remove entries matched by right argument from array</entry>
</row>
<row>
<entry><literal>int[] - int[]</literal></entry>
<entry>remove right array from left</entry>
</row>
<row>
<entry><literal>int[] | int</literal></entry>
<entry>returns intarray - union of arguments</entry>
</row>
<row>
<entry><literal>int[] | int[]</literal></entry>
<entry>returns intarray as a union of two arrays</entry>
</row>
<row>
<entry><literal>int[] & int[]</literal></entry>
<entry>returns intersection of arrays</entry>
</row>
<row>
<entry><literal>int[] @@ query_int</literal></entry>
<entry>
returns TRUE if array satisfies query (like
<literal>'1&(2|3)'</literal>)
</entry>
</row>
<row>
<entry><literal>query_int ~~ int[]</literal></entry>
<entry>returns TRUE if array satisfies query (commutator of @@)</entry>
</row>
</tbody>
</tgroup>
</table>
<para>
(Before PostgreSQL 8.2, the containment operators @> and <@ were
respectively called @ and ~. These names are still available, but are
deprecated and will eventually be retired. Notice that the old names
are reversed from the convention formerly followed by the core geometric
datatypes!)
</para>
</sect2>
<sect2>
<title>Example</title>
<programlisting>
CREATE TABLE message (mid INT NOT NULL,sections INT[]);
CREATE TABLE message_section_map (mid INT NOT NULL,sid INT NOT NULL);
-- create indices
CREATE unique index message_key ON message ( mid );
CREATE unique index message_section_map_key2 ON message_section_map (sid, mid );
CREATE INDEX message_rdtree_idx ON message USING GIST ( sections gist__int_ops);
-- select some messages with section in 1 OR 2 - OVERLAP operator
SELECT message.mid FROM message WHERE message.sections && '{1,2}';
-- select messages contains in sections 1 AND 2 - CONTAINS operator
SELECT message.mid FROM message WHERE message.sections @> '{1,2}';
-- the same, CONTAINED operator
SELECT message.mid FROM message WHERE '{1,2}' <@ message.sections;
</programlisting>
</sect2>
<sect2>
<title>Benchmark</title>
<para>
subdirectory bench contains benchmark suite.
</para>
<programlisting>
cd ./bench
1. createdb TEST
2. psql TEST < ../_int.sql
3. ./create_test.pl | psql TEST
4. ./bench.pl - perl script to benchmark queries, supports OR, AND queries
with/without RD-Tree. Run script without arguments to
see availbale options.
a)test without RD-Tree (OR)
./bench.pl -d TEST -c -s 1,2 -v
b)test with RD-Tree
./bench.pl -d TEST -c -s 1,2 -v -r
BENCHMARKS:
Size of table <message>: 200000
Size of table <message_section_map>: 269133
Distribution of messages by sections:
section 0: 74377 messages
section 1: 16284 messages
section 50: 1229 messages
section 99: 683 messages
old - without RD-Tree support,
new - with RD-Tree
+----------+---------------+----------------+
|Search set|OR, time in sec|AND, time in sec|
| +-------+-------+--------+-------+
| | old | new | old | new |
+----------+-------+-------+--------+-------+
| 1| 0.625| 0.101| -| -|
+----------+-------+-------+--------+-------+
| 99| 0.018| 0.017| -| -|
+----------+-------+-------+--------+-------+
| 1,2| 0.766| 0.133| 0.628| 0.045|
+----------+-------+-------+--------+-------+
| 1,2,50,65| 0.794| 0.141| 0.030| 0.006|
+----------+-------+-------+--------+-------+
</programlisting>
</sect2>
<sect2>
<title>Authors</title>
<para>
All work was done by Teodor Sigaev (<email>teodor@stack.net</email>) and Oleg
Bartunov (<email>oleg@sai.msu.su</email>). See
<ulink url="http://www.sai.msu.su/~megera/postgres/gist"></ulink> for
additional information. Andrey Oktyabrski did a great work on adding new
functions and operations.
</para>
</sect2>
</sect1>
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