Re: Relation cache invalidation on replica

On 27 February 2016 at 00:33, Simon Riggs <simon(at)2ndquadrant(dot)com> wrote:

> On 27 February 2016 at 00:29, Andres Freund <andres(at)anarazel(dot)de> wrote:
>
>> On 2016-02-26 18:05:55 +0300, Konstantin Knizhnik wrote:
>> > The reason of the problem is that invalidation messages are not
>> delivered to
>> > replica after the end of concurrent create index.
>> > Invalidation messages are included in xlog as part of transaction commit
>> > record.
>> > Concurrent index create is split into three transaction, last of which
>> is
>> > just performing inplace update of index tuple, marking it as valid and
>> > invalidating cache. But as far as this transaction is not assigned XID,
>> no
>> > transaction record is created in WAL and send to replicas. As a result,
>> > replica doesn't receive this invalidation messages.
>>
>> Ugh, that's a fairly ugly bug.
>
>
> Looking now.
>

If the above is true, then the proposed fix wouldn't work either.

No point in sending a cache invalidation message on the standby if you
haven't also written WAL, since the catalog re-read would just see the old
row.

heap_inplace_update() does write WAL, which blows away the starting premise.

So I'm not seeing this as an extant bug in an open source version of
PostgreSQL, in my current understanding.

--
Simon Riggs http://www.2ndQuadrant.com/
<http://www.2ndquadrant.com/>
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services