Marc Cousin <cousinmarc@xxxxxxxxx> wrote: > to sum it up, should I keep these values (I hate doing this :) ) ? Many people need to set the random_page_cost and/or seq_page_cost to reflect the overall affect of caching on the active portion of the data. We set our fully-cached databases to 0.1 for both. Databases with less caching usually wind up at 2 and 1. We have one database which does best at 0.5 and 0.3. My advice is to experiment and try to find a pair of settings which works well for most or all of your queries. If you have a few which need a different setting, you can set a special value right before running the query, but I've always been able to avoid that (thankfully). > Would there be a way to approximately evaluate them regarding to > the expected buffer hit ratio of the query ? Nothing query-specific except setting them on the connection right before the query (and setting them back or discarding the connection afterward). Well, that and making sure that effective_cache_size reflects reality. -Kevin -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
