Re: [PATCH 10/16] Introduce the concept that wal has a 'origin' node - Mailing list pgsql-hackers

On Wednesday, June 20, 2012 03:42:39 PM Robert Haas wrote:
> On Wed, Jun 20, 2012 at 9:25 AM, Simon Riggs <simon@2ndquadrant.com> wrote:
> > On 20 June 2012 21:19, Robert Haas <robertmhaas@gmail.com> wrote:
> >> On Wed, Jun 20, 2012 at 5:47 AM, Simon Riggs <simon@2ndquadrant.com> 
wrote:
> >>> The idea that logical rep is some kind of useful end goal in itself is
> >>> slightly misleading. If the thought is to block multi-master
> >>> completely on that basis, that would be a shame. Logical rep is the
> >>> mechanism for implementing multi-master.
> >> 
> >> If you're saying that single-master logical replication isn't useful,
> >> I disagree.  Of course, having both single-master and multi-master
> >> replication together is even more useful.
> >> 
> >> But I think getting even
> >> single-master logical replication working well in a single release
> >> cycle is going to be a job and a half.
> >> Thinking that we're going to
> >> get MMR in one release is not realistic.
> > If you block it, then the above becomes true, whether or not it starts
> > true.
> My main point in bringing this up is that if you pick a project that
> is too large, you will fail.
Were not the only ones here that are performing scope creep though... I think 
about all people who have posted in the whole thread except maybe Tom and 
Marko are guilty of doing so.

I still think its rather sensible to focus on exactly duplicated schemas in a 
very first version just because that leaves out some of the complexity while 
paving the road for other nice things.

> You've got four people objecting to this patch now, all of whom happen
> to be committers.  Whether or not MMR goes into core, who knows, but
> it doesn't seem that this patch is going to fly.
I find that a bit too early to say. Sure it won't fly exactly as proposed, but 
hell, who cares? What I want to get in is a solution to the specific problem 
the patch targets. At least you have, not sure about others, accepted that the 
problem needs a solution.
We do not agree yet how that solution looks should like but thats not exactly 
surprising as we started discussing the problem only a good day ago.

If people agree that your proposed way of just one flag bit is the way to go 
we will have to live with that. But thats different from saying the whole 
thing is dead.

> As I would rather see this project
> succeed, I recommend that you don't do that.  Both you and Andres seem
> to believe that MMR is a reasonable first target to shoot at, but I
> don't think anyone else - including the Slony developers who have
> commented on this issue - endorses that position. 
I don't think we get full MMR into 9.3. What I am proposing is that we build 
in the few pieces that are required to implement MMR *ontop* of whats 
hopefully in 9.3.
And I think thats a realistic goal.

> At PGCon, you were
> talking about getting a new set of features into PG over the next 3-5
> years.  Now, it seems like you want to compress that timeline to a
> year.
Well, I obviously would like to be everything be done in a release, but I also 
would like to go hiking for a year, have a restored sailing boat and some 
more. That doesn't make it reality...
To make it absolutely clear: I definitely don't think its realistic to have 
everything in 9.3. And I don't think Simon does so either. What I want is to 
have the basic building blocks in 9.3.
The difference probably just is whats determined as a building block.

Andres

-- Andres Freund                       http://www.2ndQuadrant.com/PostgreSQL Development, 24x7 Support, Training &
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