On Fri, Aug 24, 2012 at 6:36 PM, Tomas Vondra <t...@fuzzy.cz> wrote: > attached is a patch that improves performance when dropping multiple > tables within a transaction. Instead of scanning the shared buffers for > each table separately, the patch removes this and evicts all the tables > in a single pass through shared buffers. > > Our system creates a lot of "working tables" (even 100.000) and we need > to perform garbage collection (dropping obsolete tables) regularly. This > often took ~ 1 hour, because we're using big AWS instances with lots of > RAM (which tends to be slower than RAM on bare hw). After applying this > patch and dropping tables in groups of 100, the gc runs in less than 4 > minutes (i.e. a 15x speed-up). > > This is not likely to improve usual performance, but for systems like > ours, this patch is a significant improvement.
Seems pretty reasonable. But instead of duplicating so much code, couldn't we find a way to use replace DropRelFileNodeAllBuffers with DropRelFileNodeAllBuffersList? Surely anyone who was planning to call the first one could instead call the second one with a count of one and a pointer to the address of the data they were planning to pass. I'd probably swap the order of arguments to DropRelFileNodeAllBuffersList as well. We could do something similar with smgrdounlink/smgrdounlinkall so that, again, only one copy of the code is needed. -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
