Horton

Re: support for MERGE

Alvaro Herrera <alvherre@alvh.no-ip.org>

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From: Alvaro Herrera <alvherre@alvh.no-ip.org>
To: Justin Pryzby <pryzby@telsasoft.com>, Amit Langote <amitlangote09@gmail.com>, Japin Li <japinli@hotmail.com>
Cc: Zhihong Yu <zyu@yugabyte.com>, Simon Riggs <simon.riggs@enterprisedb.com>, Pg Hackers <pgsql-hackers@lists.postgresql.org>, Tomas Vondra <tomas.vondra@enterprisedb.com>, Daniel Westermann <dwe@dbi-services.com>, Erik Rijkers <er@xs4all.nl>, Jaime Casanova <jcasanov@systemguards.com.ec>, Andres Freund <andres@anarazel.de>
Date: 2022-03-17T18:36:48Z
Lists: pgsql-hackers 
On 2022-Mar-17, Alvaro Herrera wrote:

> I'll see what to do about Instrumentation->nfiltered{1,2,3} that was
> complained about by Andres upthread.  Maybe some additional macros will
> help.

This turns out not to be as simple as I expected, mostly because we want
to keep Instrumentation as a node-agnostic struct.  Things are already a
bit wonky with nfiltered/nfiltered2, and the addition of nfiltered3
makes things a lot uglier, and my impulse of using a union to separate
what is used for scans/joins vs. what is used for MERGE results in an
even more node-specific definition rather than the other way around.

Looking at the history I came across this older thread where this was
discussed
https://postgr.es/m/20180409215851.idwc75ct2bzi6tea@alvherre.pgsql
particularly this message from Robert,
https://www.postgresql.org/message-id/CA%2BTgmoaE3R6%3DV0G6zbht2L_LE%2BTsuYuSTPJXjLW%2B9_tpMGubZQ%40mail.gmail.com

I'll keep looking at this in the coming days, see if I can come up with
something sensible.

-- 
Álvaro Herrera           39°49'30"S 73°17'W  —  https://www.EnterpriseDB.com/
Y una voz del caos me habló y me dijo
"Sonríe y sé feliz, podría ser peor".
Y sonreí. Y fui feliz.
Y fue peor.

Commits

  1. Doc fixes for MERGE statement

  2. MERGE docs adjustments

  3. Link to MVCC docs in MERGE docs

  4. Fix EXPLAIN MERGE output when no tuples are processed

  5. Make EXPLAIN MERGE output format more compact

  6. Add support for MERGE SQL command

  7. Split ExecUpdate and ExecDelete into reusable pieces

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

  9. Represent Lists as expansible arrays, not chains of cons-cells.