On 19 October 2013 19:22, Peter Geoghegan <p...@heroku.com> wrote: > I won't repeat the rationale for the patch here.
I can't see the problem that this patch is trying to solve. I'm having trouble understanding when I would use this. VACUUM uses 6 bytes per dead tuple. And autovacuum regularly removes dead tuples, limiting their numbers. In what circumstances will the memory usage from multiple concurrent VACUUMs become a problem? In those circumstances, reducing autovacuum_work_mem will cause more passes through indexes, dirtying more pages and elongating the problem workload. I agree that multiple concurrent VACUUMs could be a problem but this doesn't solve that, it just makes things worse. Freezing doesn't require any memory at all, so wraparound vacuums won't be controlled by this parameter. Can we re-state what problem actually is here and discuss how to solve it. (The reference [2] didn't provide a detailed explanation of the problem, only the reason why we want a separate parameter). -- Simon Riggs http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Training & Services -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
