On Fri, Mar 23, 2007 at 02:13:57PM +0100, Henrik Zagerholm wrote: > I'm just amazed that setting the statistics threshold on one column > mad all the difference. IS there any guidelines on what columns I > should change the statistics on?
Start by looking for columns involved in simple comparisons with a constant -- especially if you know that the distribution of values is uneven -- and see how far off the row count estimate is for various values. You can use simple queries such as EXPLAIN ANALYZE SELECT 1 FROM tbl_file WHERE fk_filetype_id = 83; To learn more read "How the Planner Uses Statistics" in the documentation: http://www.postgresql.org/docs/8.2/interactive/planner-stats-details.html Among the configuration settings to consider changing are shared_buffers, effective_cache_size, work_mem, and random_page_cost. The following is a good starting point: http://www.powerpostgresql.com/PerfList If you have additional performance-related questions then consider posting to pgsql-performance. -- Michael Fuhr ---------------------------(end of broadcast)--------------------------- TIP 4: Have you searched our list archives? http://archives.postgresql.org/
