Re: index-only scans vs. Hot Standby, round two

On Mon, Apr 16, 2012 at 1:58 PM, Simon Riggs <simon@2ndquadrant.com> wrote:
> If we do need to do something, then introduce concept of a visibility conflict.
>
> On replay:
> If feedback not set, set LSN of visibility conflict on PROCs that
> conflict, if not already set.
>
> On query:
> If feedback not set, check conflict LSN against page, if page is
> later, check visibility.

Hmm, should have read the whole thread before replying.  This similar
to what I just proposed in response to Heikki's message, but using LSN
in lieu of (or maybe you mean in addition to) XID.

I don't think we can ignore the need to throw conflicts just because
hot_standby_feedback is set; there are going to be corner cases, for
example, when it's just recently been turned on and the master has
already done cleanup; or if the master and standby have recently
gotten disconnected for even just a few seconds.

But fundamentally we all seem to be converging on some variant of the
"soft conflict" idea.

-- 
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company