On Tue, Nov 13, 2012 at 11:13 AM, Jon Nelson <jnelson+pgsql@xxxxxxxxxxx> wrote: > I was working on a data warehousing project where a fair number of files > could be COPY'd more or less directly into tables. I have a somewhat nice > machine to work with, and I ran on 75% of the cores I have (75% of 32 is > 24). > > Performance was pretty bad. With 24 processes going, each backend (in COPY) > spent 98% of it's time in semop (as identified by strace). They are probably fighting over the right to insert records into the WAL stream. This has been improved in 9.2 > Given that each COPY is into it's own, newly-made table with no indices or > foreign keys, etc, I would have expected the interaction among the backends > to be minimal, but that doesn't appear to be the case. On newer versions if you set wal_level to minimal and archive_mode to off, then these operations would bypass WAL entirely. I can't figure out if there is a corresponding optimization in 8.4, though. Cheers, Jeff -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
