Re: Re: Hot Standby query cancellation and Streaming Replication integration

Josh Berkus <josh@agliodbs.com> writes:
> On 2/26/10 10:53 AM, Tom Lane wrote:
>> I think that what we are going to have to do before we can ship 9.0
>> is rip all of that stuff out and replace it with the sort of closed-loop
>> synchronization Greg Smith is pushing.  It will probably be several
>> months before everyone is forced to accept that, which is why 9.0 is
>> not going to ship this year.

> I don't think that publishing visibility info back to the master ... and
> subsequently burdening the master substantially for each additional
> slave ... are what most users want.

I don't see a "substantial additional burden" there.  What I would
imagine is needed is that the slave transmits a single number back
--- its current oldest xmin --- and the walsender process publishes
that number as its transaction xmin in its PGPROC entry on the master.

I don't doubt that this approach will have its own gotchas that we
find as we get into it.  But it looks soluble.  I have no faith in
either the correctness or the usability of the approach currently
being pursued.
        regards, tom lane