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From: Josh Berkus <josh@agliodbs.com>
To: Alvaro Herrera <alvherre@2ndquadrant.com>
Cc: pgsql-hackers@postgresql.org
Subject: Re: Need Multixact Freezing Docs
Date: Wed, 16 Apr 2014 11:06:19 -0700
Message-ID: <534EC69B.9010107@agliodbs.com> (raw)
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> You can see the current multixact value in pg_controldata output.  Keep
> timestamped values of that somewhere (a table?) so that you can measure
> consumption rate.  I don't think we provide SQL-level access to those
> values.

Bleh.  Do we provide SQL-level access in 9.4?  If not, I think that's a
requirement before release.  Telling users to monitor a setting using a
restricted-permission command-line utility which produces a
version-specific text file they have to parse is not going to win us a
lot of fans.

> 
>> Also: how do I check the multixact age of a table?  There doesn't seem
>> to be any data for this ...
> 
> pg_class.relminmxid is the oldest multixact value that might be present
> in a table.

On every database I've tested, age(relminmxid) returns int_max.  So this
is apparently broken.

-- 
Josh Berkus
PostgreSQL Experts Inc.
http://pgexperts.com


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