Re: pg_multixact not getting truncated

On 11/05/2014 11:15 AM, Josh Berkus wrote:
> On 11/05/2014 10:40 AM, Jim Nasby wrote:
>> Can you post the contents of pg_multixact/members/?
> 
> Well, not as of last week, obviously.
> 
> https://gist.github.com/jberkus/d05db3629e8c898664c4
> 
> I haven't pasted all the filenames, because, well, look at the count.  I
> also added the contents of the /offsets directory, for full information.
> 
> Note that we've added 400 multixact files since my first email.

So, just did a quick survey of our managed services customers.  4 out of
6 have pg_multixact bloat.  Basically it looks like this:

User1 (the one above): 1.1GB
User2: 64K
User3: 929MB
User4: 1.3GB
User5: 301MB
User6: 48K

Nobody (out of 6 more) running a version older than 9.3 had a
pg_multixact larger than 128K.

None of these users used pg_upgrade, so that's not the source of this
problem.  Instead, as demonstrated earlier, we are simply not truncating
pg_multixact sufficiently.

So this looks like a pretty serious bug.

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