Thanks for the quick response, Andrew. How could the 'commit prepared' be I/O bound? Isn't all the I/O accomplished during 'prepare transaction', leaving only a tiny bit of data to write at commit? > > You could be I/O bound. Have a look at iostat and sar. > > A > -- > Andrew Sullivan > ajs(at)crankycanuck(dot)ca > > > > On Tue, Nov 25, 2008 at 7:17 PM, John Smith <sodgodofall@xxxxxxxxx> wrote: > > I have a pg instance with 700GB of data, almost all of which is in one > > table. When I PREPARE and then COMMIT PREPARED a transaction that > > reads & writes to a large fraction of that data (about 10%, > > effectively randomly chosen rows and so every file in the table is > > modified), the COMMIT PREPARED sometimes takes a very long time--2 to > > 5 minutes. Is this expected? Is it possible for the commit to hang > > waiting on some lock for this long? I haven't yet been able to examine > > pg_locks during this 5 minute delay. There is very little > > concurrency--only a couple of open sessions--when the COMMIT PREPARED > > is issued. > > > > Thanks for your help, > > John > > > -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
