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From: Alvaro Herrera <alvherre@2ndquadrant.com>
To: Jeff Janes <jeff.janes@gmail.com>
Cc: Serge Negodyuck <petr@petrovich.kiev.ua>
Cc: Pg Bugs <pgsql-bugs@postgresql.org>
Subject: Re: BUG #8673: Could not open file "pg_multixact/members/xxxx" on slave during hot_standby
Date: Mon, 9 Jun 2014 18:50:39 -0400
Message-ID: <20140609225039.GC18688@eldon.alvh.no-ip.org> (raw)
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References: <20131209142525.GA1123@awork2.anarazel.de>
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	<20131209182701.GD9519@awork2.anarazel.de>
	<20140103014616.GB7035@eldon.alvh.no-ip.org>
	<CABKyZDEV49nUYJej9Hv-hPUS=VUmMt1LmVV=YW=fV5X8nKtdtw@mail.gmail.com>
	<20140606013943.GT5146@eldon.alvh.no-ip.org>
	<20140606164727.GU5146@eldon.alvh.no-ip.org>
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Jeff Janes wrote:

> This patch seems to solve a problem I've also been having with non-existent
> "pg_multixact/members/13D35" files in my testing of torn page write and fk
> locks again recent 9.4.  However, sometimes I've found the problem even
> before multi wrap around occured, and my reading of this thread suggests
> that the current issue would not show up in that case, so I don't know how
> much comfort to take in the knowledge that the problem seems to have gone
> away--as they say, things that go away by themselves without explanation
> also tend to come back by themselves.

I think this problem is rather related to the code touched by commit
722acf51a0d074d19782ad7e97ebe3fdb63fbb87, which is about removing
unneeded files in pg_multixact/members.  I checked your files, and it
seems that pg_multixact/members files that should still exist are gone;
for instance, pg_controldata says that the oldest multi is 2586314407,
but if I run
select * from pg_get_multixact_members('that value')
I get an error saying that pg_multixact/members/218B does not exist.

It seems that there are a lot of files that were improperly removed.
I expect that existing files should be sequential, but there are a lot
of holes in a listing of pg_multixact/members.

-- 
Álvaro Herrera                http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services


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  Cc: alvherre@2ndquadrant.com, jeff.janes@gmail.com, petr@petrovich.kiev.ua, pgsql-bugs@postgresql.org
  Subject: Re: BUG #8673: Could not open file "pg_multixact/members/xxxx" on slave during hot_standby
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