Re: MERGE SQL Statement for PG11

From: Simon Riggs <simon(at)2ndquadrant(dot)com>
To: Robert Haas <robertmhaas(at)gmail(dot)com>
Cc: Peter Geoghegan <pg(at)bowt(dot)ie>, Michael Paquier <michael(dot)paquier(at)gmail(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: MERGE SQL Statement for PG11
Date: 2017-10-30 13:21:20
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On 30 October 2017 at 09:44, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
> On Sun, Oct 29, 2017 at 1:19 AM, Simon Riggs <simon(at)2ndquadrant(dot)com> wrote:
>> Nothing I am proposing blocks later work.
> That's not really true. Nobody's going to be happy if MERGE has one
> behavior in one set of cases and an astonishingly different behavior
> in another set of cases. If you adopt a behavior for certain cases
> that can't be extended to other cases, then you're blocking a
> general-purpose MERGE.

If a general purpose solution exists, please explain what it is. The
problem is that nobody has ever done so, so its not like we are
discussing the difference between bad solution X and good solution Y,
we are comparing reasonable solution X with non-existent solution Y.

> And, indeed, it seems that you're proposing an implementation that
> adds no new functionality, just syntax compatibility. Do we really
> want or need two syntaxes for the same thing in core? I kinda think
> Peter might have the right idea here. Under his proposal, we'd be
> getting something that is, in a way, new.

Partitioning looked like "just new syntax", but it has been a useful
new feature.

MERGE provides new capabilities that we do not have and is much more
powerful than INSERT/UPDATE, in a syntax that follow what other
databases use today. Just like partitioning.

Will what I propose do everything in the first release? No, just like

If other developers are able to do things in phases, then I claim that
right also.

Simon Riggs
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services

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