Horton

Re: [HACKERS] MERGE SQL Statement for PG11

Peter Geoghegan <pg@bowt.ie>

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From: Peter Geoghegan <pg@bowt.ie>
To: Alvaro Herrera <alvherre@alvh.no-ip.org>
Cc: Simon Riggs <simon@2ndquadrant.com>, Pavan Deolasee <pavan.deolasee@gmail.com>, Robert Haas <robertmhaas@gmail.com>, Tomas Vondra <tomas.vondra@2ndquadrant.com>, Andrew Dunstan <andrew.dunstan@2ndquadrant.com>, Pavan Deolasee <pavan.deolasee@2ndquadrant.com>, Stephen Frost <sfrost@snowman.net>, PostgreSQL-development <pgsql-hackers@postgresql.org>
Date: 2018-03-23T01:15:54Z
Lists: pgsql-hackers 
On Thu, Mar 22, 2018 at 6:02 PM, Alvaro Herrera <alvherre@alvh.no-ip.org> wrote:
> Incremental development is a good thing.  Trying to do everything in a
> single commit is great when time is infinite or even merely very long,
> but if you run out of it, which I'm sure is common, leaving some things
> out that can be reasonable implemented in a separate patch is perfectly
> acceptable.

We're talking about something that took me less than an hour to get
working. AFAICT, it's just a matter of tweaking the grammar, and
adding a bit of transformWithClause() boilerplate to the start of
transformMergeStmt().

As I've pointed out on this thread already, I'm often concerned about
supporting functionality like this because it increases my overall
confidence in the design. If it was genuinely hard to add WITH clause
support, then that would probably tell us something about the overall
design that likely creates problems elsewhere. It's easy to say that
it isn't worth holding the patch up for WITH clause support, because
that's true, but it's also beside the point.

-- 
Peter Geoghegan

Commits

  1. Add support for MERGE SQL command

  2. Add API of sorts for transition table handling in trigger.c

  3. Revert MERGE patch

  4. Fix several bugs related to ON CONFLICT's EXCLUDED pseudo relation.