Re: Slow standby snapshot - Mailing list pgsql-hackers

From Simon Riggs
Subject Re: Slow standby snapshot
Date
Msg-id CANbhV-Ey8HRYPvnvQnsZAteCfzN3VHVhZVKfWMYcnjMnSzs4dQ@mail.gmail.com
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In response to Re: Slow standby snapshot  (Andrey Borodin <x4mmm@yandex-team.ru>)
Responses Re: Slow standby snapshot
Re: Slow standby snapshot
List pgsql-hackers
On Tue, 2 Aug 2022 at 12:32, Andrey Borodin <x4mmm@yandex-team.ru> wrote:

> KnownAssignedXidsRemoveTree() only compress with probability 1/8, but it is still O(N*N).

Currently it is O(NlogS), not quite as bad as O(N^2).

Since each xid in the tree is always stored to the right, it should be
possible to make that significantly better by starting each binary
search from the next element, rather than the start of the array.
Something like the attached might help, but we can probably make that
cache conscious to improve things even more.

-- 
Simon Riggs                http://www.EnterpriseDB.com/

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