Torsten Förtsch <torsten.foertsch@xxxxxxx> wrote: > Is there an other way to make the planner use generate the 1st > plan? The planner cost factors are based on the assumption that a moderate percentage of random page reads will need to actually go out to disk. If a high percentage of pages are in cache, you may want to reduce random_page_cost to something closer to (or even equal to) seq_page_cost. I generally find I get better plans if I raise cpu_tuple_cost to 0.03. effective_cache_size should generally be between 50% and 75% of machine RAM. If these changes (or others of their ilk) cause costs to be estimated in a way which more nearly matches reality, better plans will be chosen. > Why does it generate the 2nd plan at all? It has the lowest estimated cost, based on your memory configuration and cost factors. > Does the planner take into account what is currently present in > shared memory? No. If you search the archives you can probably find previous discussions of whether it would be a good idea to do so; the consensus has been that it would not be. If you have further performance-related questions, please review this page so that you can provide enough information to allow people to give the most helpful advice: http://wiki.postgresql.org/wiki/SlowQueryQuestions -- Kevin Grittner EDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
