Horton

Re: [HACKERS] MERGE SQL Statement for PG11

Robert Haas <robertmhaas@gmail.com>

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From: Robert Haas <robertmhaas@gmail.com>
To: Peter Geoghegan <pg@bowt.ie>
Cc: Andres Freund <andres@anarazel.de>, Simon Riggs <simon@2ndquadrant.com>, Tom Lane <tgl@sss.pgh.pa.us>, Pavan Deolasee <pavan.deolasee@gmail.com>, 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: 2018-04-03T03:01:50Z
Lists: pgsql-hackers 
On Mon, Apr 2, 2018 at 10:40 PM, Peter Geoghegan <pg@bowt.ie> wrote:
> On Mon, Apr 2, 2018 at 7:18 PM, Andres Freund <andres@anarazel.de> wrote:
>> I did a scan through this, as I hadn't been able to keep with the thread
>> previously. Sorry if some of the things mentioned here have been
>> discussed previously. I am just reading through the patch in its own
>> order, so please excuse if there's things I remark on that only later
>> fully make sense.
>>
>>
>> later update: TL;DR: I don't think the parser / executor implementation
>> of MERGE is architecturally sound.  I think creating hidden joins during
>> parse-analysis to implement MERGE is a seriously bad idea and it needs
>> to be replaced by a different executor structure.
>
> +1. I continue to have significant misgivings about this. It has many
> consequences that we know about, and likely quite a few more that we
> don't.

+1.  I didn't understand from Peter's earlier comments that we were
doing that, and I agree that it isn't a good design choice.

-- 
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company

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.