On May 09, Sterpu Victor modulated: > I tested it now, EXPLAIN ANALYZE is not showing LEFT JOIN at all if > I don't select from the joined tables. > Now is clear why the query is so mutch more efficient when I select > less data. > > Thank you >
With so many joins, you may want to experiment with postgresql parameter tuning. These parameters in particular can have a significant impact on the plan choice and execution time: work_mem effective_cache_size from_collapse_limit join_collapse_limit geqo_threshold geqo_effort Setting these to appropriately large values can make analytic queries run much faster. Of course, setting them too high can also make for very bad plans which cause the DB server to over subscribe its memory and start swapping... it requires a bit of reading and a bit of experimentation to find ideal settings for your environment. Karl -- Sent via pgsql-general mailing list (pgsql-general@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
