Can PostgreSQL index array columns?

Question

I can\'t find a definite answer to this question in the documentation. If a column is an array type, will all the entered values be individually indexed?

I created a

Answer 1

It's now possible to index the individual array elements. For example:

CREATE TABLE test (foo int[]);
INSERT INTO test VALUES ('{1,2,3}');
INSERT INTO test VALUES ('{4,5,6}');
CREATE INDEX test_index on test ((foo[1]));
SET enable_seqscan TO off;

EXPLAIN ANALYZE SELECT * from test WHERE foo[1]=1;
                                                QUERY PLAN                                                    
------------------------------------------------------------------------------------------------------------------
 Index Scan using test_index on test  (cost=0.00..8.27 rows=1 width=32) (actual   time=0.070..0.071 rows=1 loops=1)
   Index Cond: (foo[1] = 1)
 Total runtime: 0.112 ms
(3 rows)

This works on at least Postgres 9.2.1. Note that you need to build a separate index for each array index, in my example I only indexed the first element.