Re: Hot Standby (v9d)

On Tue, Feb 3, 2009 at 9:40 AM, Simon Riggs <simon(at)2ndquadrant(dot)com> wrote:
> On Tue, 2009-02-03 at 09:14 -0500, Robert Haas wrote:
>> I think _the_ solution is to notice when you're about to vacuum a page
>> that is still visible to a running backend on the standby, and save
>> that page off to a separate cache of old page versions (perhaps using
>> the relation fork mechanism).
>
> I'll let you write that, for the next release...

LOL. How many sponsorship dollars are available for that project?

> The problem with all of this is we've been talking about it for 8 months
> now and various opinions are held by people. What is being presented is
> a broad set of options (summarised from Wiki)

I think everyone understands that these are things we might want to do
down the line, not things we need to have now. For this release, I
was under the impression that we'd pretty much settled on implementing
(1) and maybe (3) but not (2) from the below list.

> 1. Wait then cancel
> a) always for databases, tablespaces and locks
> b) deferred cancelation for buffer changes
>
> 2. We connect to Primary server from Standby server and keep a
> transaction open using contrib/dblink functions, then commit as soon as
> we are done.
>
> 3. We pause recovery by issuing a pg_recovery_pause() function, or start
> server in pause mode using recovery_started_paused = on.
>
> Yes, it's a critical area to the success of the feature. But this is
> enough for first release and for us to get user feedback.

I completely agree.

...Robert