Hail there, Short question: Why would pg optimizer choose a worst (slower) query plan for a query with 'LIMIT 1' instead of, say, 'LIMIT 3'?
Complete scenario: Query: 'SELECT * FROM a WHERE a.b_id = 42 ORDER BY created LIMIT 1' - b_id is a FK to b; - created is a datetime with the time of the creation of the row; - both 'b' and 'created' are indexed separately This query, with the LIMIT 1, uses the index on created, which is much slower (10x) than if it used the index on b_id If I change the LIMIT from 1 to 3 pg starts using the index on b_id. Already tried running REINDEX and VACUUM ANALYZE on both A and B. Nothing changed. Why does this happen? Is there any way I can hint/force the optimizer to use b_id index? Thanks -- Marcio Ribeiro
