How many rows do you have in that table? I think , that planner thinks that the element you are looking for is so common - that it will be to expensive to use index to fetch it. Perhaps try increasing default_statistics_target , and revacuuming the table.
You could also try changing it just for the column: ALTER TABLE records ALTER id SET source_id 1000; vacuum analyze verbose records; -- Sent via pgsql-performance mailing list (pgsql-performance@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
