On Mon, May 10, 2010 at 11:32 PM, Carlo Stonebanks <stonec.regis...@sympatico.ca> wrote: > Hello all, > > A query ran twice in succession performs VERY poorly the first time as it > iterates through the nested loop. The second time, it rips. Please see SQL, > SLOW PLAN and FAST PLAN below.
This is almost always due to caching. First time the data aren't in the cache, second time they are. > I don't know why these nested loops are taking so long to execute. > " -> Nested Loop (cost=0.00..42866.98 rows=77 width=18) (actual > time=126.354..26301.027 rows=9613 loops=1)" > " -> Nested Loop (cost=0.00..42150.37 rows=122 width=18) (actual > time=117.369..15349.533 rows=13247 loops=1)" Your row estimates are WAY off. A nested loop might now be the best choice. Also note that some platforms add a lot of time to some parts of an explain analyze due to slow time function response. Compare the run time of the first run with and without explain analyze. -- Sent via pgsql-performance mailing list (pgsql-performance@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
