On Sat, Jun 13, 2009 at 12:12 AM, Erik Jones<ejo...@engineyard.com> wrote: > > On Jun 9, 2009, at 10:51 AM, Rob Sargent wrote: > >> Caching helps a *lot* and I'm thankful for that but I would like to take >> it out of the picture as I massage my queries for better performance. >> Naturally the first invocation of the query cannot take advantage of the >> cache and these queries would normally only be called once for the same >> target data. What tricks are there to flush, ignore, circumvent the >> caching boost? (Especially in the production environment.) > > Why on earth would you want your queries to always go to disk?
I think he answered that in the original message -- to better represent the real workload. Unfortunately there isn't really a good answer. On Linux you can echo 1 > /proc/sys/vm/drop_caches but that doesn't affect the postgres shared buffers and worse, it does affect other buffers that probably would still be cached. The best answer is usually to build a test configuration large enough that it has similar cache effects as your production environment. Then test random values and repeat the test many times to avoid any random fluctuations. -- greg http://mit.edu/~gsstark/resume.pdf -- Sent via pgsql-sql mailing list (pgsql-sql@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-sql
