NOTIFY performance

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