On Fri, Aug 24, 2012 at 1:46 PM, Artur Zając <azajac@xxxxxxxxxx> wrote: > Hello, > > > I would like to create some application using triggers and LISTEN/NOTIFY > framework. I've tested it, and I noticed that performance of NOTIFY > significally decreases with increasing number of distinct NOTIFIES in > transaction. > I found that function AsyncExistsPendingNotify is responsibe for it. I think > that complexivity of searching duplicates there is O(N^2). Would be possible > to improve performance of it? Maybe by using list for elements precedence > and binary search tree for searching duplicates - with complexivity of > O(Nlog2(N)). > > I'v tested with 50000 of NOTICES. Updating table with 20000 NOTICES when > searching is not performed took 1,5 second. With searching it took 28 > seconds. I've confirmed the n^2 behavior on 9.2: postgres=# select pg_notify(v::text, null) from generate_series(1,10000) v; Time: 281.000 ms postgres=# select pg_notify(v::text, null) from generate_series(1,50000) v; Time: 7148.000 ms ...but i'm curious if you're going about things the right way...typically I'd imagine you'd write out actionable items to a table and issue a much broader NOTIFY which taps listeners on the table to search the action queue. Could you describe your problem in a little more detail? merlin -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
