On 05/30/15 01:20, Tomas Vondra wrote:
Notice the cost - it's way lover than the previous plan (9.2 vs ~111k), yet this plan was not chosen. So either the change broke something (e.g. by violating some optimizer assumption), or maybe there's a bug somewhere else ...
After a bit more investigation, what I think is happening here is add_path() does not realize this is a SEMI join and a single tuple is enough, and discards the simple indexscan path in favor of the bitmap index scan as that seems cheaper when scanning everything.
So not really a bug, but maybe 'consider_startup' would help? -- Tomas Vondra http://www.2ndQuadrant.com PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
