From: =?iso-8859-2?Q?Artur_Zaj=B1c?= <azajac@ang.com.pl>
To: <pgsql-performance@postgresql.org>
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Subject: NOTIFY performance
Date: Fri, 24 Aug 2012 20:46:42 +0200
Message-ID: <002401cd8228$ce80e970$6b82bc50$@ang.com.pl>
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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.

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Artur Zajac