Re: could not access status of transaction pg_multixact issue

From: jim_yates <pg(at)wg5jim(dot)net>
To: pgsql-sql(at)postgresql(dot)org
Subject: Re: could not access status of transaction pg_multixact issue
Date: 2014-10-10 14:37:01
Message-ID: 1412951821680-5822573.post@n5.nabble.com
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Alvaro Herrera-9 wrote
> jim_yates wrote:
>
>> Then I'm really confused.
>> The minimum relminmxid for all the rows in pg_class that have relminmxid
>> greater then zero is 1.
>> That's the current value of datminmxid in pg_database.
>>
>> And the NextMultiXactId from pg_controldump is 303464.
>>
>> So if I use the min value from pg_class then I have some other issue.
>>
>> Where should I get the new pg_database value from?
>
> I'm deep in another issue which I don't want to page out right now, but
> try vacuuming the tables that have relminmxid=1 with low values set for
> vacuum_multixact_freeze_table_age and vacuum_multixact_freeze_min_age,
> say 100000. (I think 65536 ought to get you beyond segment
> pg_multixact/offset/0000, and then that file would be removed.) Since
> any multixact values below the point at which pg_upgrade ran should be
> marked "no longer running" through hint bits, there would be no
> pg_multixact lookups anyway and thus the vacuuming should complete with
> no errors.
>
> --
> Álvaro Herrera http://www.2ndQuadrant.com/
> PostgreSQL Development, 24x7 Support, Training & Services

I set vacuum_multixact_freeze_table_age and vacuum_multixact_freeze_min_age
to 100,000 and vacuumed all the tables with a relminmxid='1' and relkind='r'
using pg_class as the source.
I still couldn't vacuum or select the original table with the issue.
I did solve the problem by dropping the table and restoring from my standby
server.

Is there else anything I need to do to prevent being bitten by this bug
again?

I still have a value of 1 for datminmxid in pg_database, and the 0000 file
is still in pg_multixact/members and offsets.

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