Horton

Re: [HACKERS] MERGE SQL Statement for PG11

Peter Geoghegan <pg@bowt.ie>

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From: Peter Geoghegan <pg@bowt.ie>
To: Pavan Deolasee <pavan.deolasee@gmail.com>
Cc: Robert Haas <robertmhaas@gmail.com>, Andres Freund <andres@anarazel.de>, Simon Riggs <simon@2ndquadrant.com>, Tom Lane <tgl@sss.pgh.pa.us>, Amit Langote <Langote_Amit_f8@lab.ntt.co.jp>, Tomas Vondra <tomas.vondra@2ndquadrant.com>, Alvaro Herrera <alvherre@alvh.no-ip.org>, Andrew Dunstan <andrew.dunstan@2ndquadrant.com>, Pavan Deolasee <pavan.deolasee@2ndquadrant.com>, Stephen Frost <sfrost@snowman.net>, PostgreSQL-development <pgsql-hackers@postgresql.org>
Date: 2018-04-03T03:18:26Z
Lists: pgsql-hackers 
On Mon, Apr 2, 2018 at 8:11 PM, Pavan Deolasee <pavan.deolasee@gmail.com> wrote:
> Honestly I don't think Peter ever raised concerns about the join, though I
> could be missing early discussions when I wasn't paying attention. It's
> there from day 1. Peter raised concerns about the two RTE stuff which was
> necessitated when we added support for partitioned table. We discussed that
> at some length, with your inputs and agreed that it's not necessarily a bad
> thing and probably the only way to deal with partitioned tables.
>
> Personally, I don't see why an internal join is bad. That's what MERGE is
> doing anyways, so it closely matches with the overall procedure.

The issue is not that there is a join as such. It's how it's
represented in the parser, and how that affects other things. There is
a lot of special case logic to make it work.


-- 
Peter Geoghegan

Commits

  1. Add support for MERGE SQL command

  2. Avoid repeated name lookups during table and index DDL.

  3. Use an MVCC snapshot, rather than SnapshotNow, for catalog scans.