On 09/12/12 4:03 PM, Sébastien Lorion wrote:
I agree 1GB is a lot, I played around with that value, but it hardly makes a difference. Is there a plateau in how that value affects query performance ? On a master DB, I would set it low and raise as necessary, but what would be a good average value on a read-only DB with same spec and max_connections ?
a complex query can require several times work_mem for sorts and hash merges. how many queries do you expect to ever be executing concurrently? I'll take 25% of my system memory and divide it by 'max_connections' and use that as work_mem for most cases.
on a large memory system doing dedicated transaction processing, I generally shoot for about 50% of the server memory as disk cache, 1-2GB as shared_buffers, 512MB-2GB as maintenance_work_mem, and 20-25% as work_mem (divided by max_connections)
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