mac_man2...@yahoo.it wrote:
Since I am interested just in work_mem variations, I should prevent each query to take advantages from revious executions of the 22 queries them selves. For example, taking cache advantages.
work_mem has nothing to do with disk caching; it controls whether larger sorts are done using disk or memory. The main parameter that controls the size of the disk cache is shared_buffers. If you found the descriptions in the manual confusing, http://wiki.postgresql.org/wiki/Tuning_Your_PostgreSQL_Server is another guide to what the settings mean that may help you out.
If you want to eliminate caching effects from your test, you will need to both restart the database server and flush the operating system cache. You can do this easily on Linux: http://linux-mm.org/Drop_Caches but it's not as simple to do on most other platforms without rebooting.
P.S. The right list for this discussion if you want to talk about it more is pgsql-performance. This one is focused at things involving PostgreSQL development, not questions related to using the database.
-- Greg Smith 2ndQuadrant US Baltimore, MD PostgreSQL Training, Services and Support g...@2ndquadrant.com www.2ndQuadrant.us -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
