Re: Multixacts wraparound monitoring

Pavlov, Vladimir wrote:
> Hello,
> If I get you right:
> Latest checkpoint's NextMultiXactId:      2075246000
> Latest checkpoint's oldestMultiXid:       2019511697
> Number of members files:    10820
> Size pg_multixact/members/ (bytes) (2.7Gb):    2887696384
> Pages in file:    32
> Members on page:    2045
> Number of members (32*2045*10820):    708060800
> Members per multixact (2075246000 - 2019511697)/708060800:    12,70421916
> Multixact size (bytes) (2887696384/708060800):    4,078316981 - It's a lot?

Yeah, 12.7 members per multixact on average is a lot, unless you have 12
processes concurrently locking the same tuples, all the time (although
that is possible).   My guess is that this is related to subtransactions
(either explicit SAVEPOINTs in your SQL code, or EXCEPTION blocks in
plpgsql functions).

--
Álvaro Herrera                http://www.2ndQuadrant.com/
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