Re: I'd like to discuss scaleout at PGCon

On 1 June 2018 at 16:56, Ashutosh Bapat <ashutosh(dot)bapat(at)enterprisedb(dot)com> wrote:
> On Fri, Jun 1, 2018 at 11:10 AM, Simon Riggs <simon(at)2ndquadrant(dot)com> wrote:
>>
>> Using a central coordinator also allows multi-node transaction
>> control, global deadlock detection etc..
>
> But that becomes an SPOF and then we have to configure a standby for
> that. I am not saying that that's a bad design but it's not very good
> for many work-loads. But it would be good if we could avoid any
> "central server" in this configuration.
>
>>
>> And that is why both XL and "FDW approach" rely on a central coordinator.
>
> I don't think we ever specified that "FDW approach" "relies" on a
> central coordinator. One could configure and setup a cluster with
> multiple coordinators using FDWs.

Yes, of course. You're just misunderstanding me. I'm talking about a
query coordinator "role". There can be many coordinator components and
they can be spread out in variours ways, but for any one SQL query
there needs to be one coordinator node. Not a SPOF.

>>
>> FDWs alone are not enough. It is clear that some more tight coupling
>> is required to get things to work well. For example, supporting SQL
>> query plans that allow for redistribution of data for joins.
>
> I think partitioning + FDW provide basic infrastructure for
> distributing data, planning queries working with such data. We need
> more glue to support node management, cluster configuration. So, I
> agree with your statement. But I think it was clear from the beginning
> that we need more than FDW and partitioning.

No, it wasn't clear. But I'm glad to hear it. It might actually work then.

--
Simon Riggs http://www.2ndQuadrant.com/
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