Re: pgsql: Improve autovacuum logging for aggressive and anti-wraparound ru

On 3/29/19 7:51 AM, Michael Paquier wrote:
> On Sat, Mar 09, 2019 at 10:15:37AM +0900, Michael Paquier wrote:
>> I am adding an open item about that. I think I could commit the
>> patch, but I need to study it a bit more first.
> So, coming back to this thread, and studying the problem again, it
> looks that the diagnostic that a non-aggressive, anti-wraparound
> vacuum could be triggered because the worker sees trouble in the
> force because of some activity happening in parallel. Hence, if we
> face this case, it looks right to skip the vacuum for this relation.
>
> Attached is an updated patch with a better error message, more
> comments, and the removal of the anti-wraparound non-aggressive log
> which was added in 28a8fa9. The error message could be better I
> guess. Suggestions are welcome.
>
> Thoughts?

+                (errmsg_internal("found vacuum to prevent wraparound of
table \"%s.%s.%s\" to be not aggressive, so skipping",

This might convey something to hackers, but I doubt it will convey much
to regular users. Perhaps something like "skipping redundant
anti-wraparound vacuum of table ..." would be better.

The comment is also a bit too tentative. Perhaps something like this
would do:

Normally the relfrozenxid for an anti-wraparound vacuum will be old
enough to force an aggressive vacuum. However, a concurrent vacuum
might have already done this work that the relfroxzenxid in relcache
has been updated. If that happens this vacuum is redundant, so skip it.

cheers

andrew

--
Andrew Dunstan https://www.2ndQuadrant.com
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services