Simon Riggs <simon@xxxxxxxxxxxxxxx> writes: > On Tue, 2008-04-01 at 13:07 +0530, Pavan Deolasee wrote: >> Please see the attached patch. One change I made is to hold the SHARE lock >> on the page while ANALYZE is reading tuples from it. I thought it would >> be a right thing to do instead of repeatedly acquiring/releasing the lock. > ANALYZE is a secondary task and so we shouldn't be speeding it up at the > possible expense of other primary tasks. So I think holding locks for > longer than minimum is not good in this case and I see no reason to make > the change described. I think Pavan's change is probably good. In the first place, it's only a shared buffer lock and besides ANALYZE isn't going to be holding it long (all it's doing at this point is counting tuples and copying some of them into memory). In the second place, repeated lock release and re-grab threatens cache line contention and a context swap storm if there is anyone else trying to access the page. In the third, whether there's contention or not the extra acquire/release work will cost CPU cycles. In the fourth, if we actually believed this was a problem we'd need to redesign VACUUM too, as it does the same thing. I haven't read the patch yet, but I'm inclined to go with the design Pavan suggests. regards, tom lane -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
