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: Pg Hackers <pgsql-hackers@lists.postgresql.org>
Cc: Simon Riggs <simon.riggs@enterprisedb.com>, Tomas Vondra <tomas.vondra@enterprisedb.com>, Zhihong Yu <zyu@yugabyte.com>, Daniel Westermann <dwe@dbi-services.com>, Amit Langote <amitlangote09@gmail.com>, Justin Pryzby <pryzby@telsasoft.com>, Japin Li <japinli@hotmail.com>, Erik Rijkers <er@xs4all.nl>, Jaime Casanova <jcasanov@systemguards.com.ec>
Date: 2022-01-28T20:27:37Z
Lists: pgsql-hackers

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MERGE, v10.  I am much more comfortable with this version; I have
removed a bunch of temporary hacks and cleaned up the interactions with
table AM and executor, which is something that had been bothering me for
a while.  The complete set of changes can be seen in github,
https://github.com/alvherre/postgres/commits/merge-15

The most important one is probably
https://github.com/alvherre/postgres/commit/1bc92bd3f5af8b0406c5a633a68b2f76ba5a2616
where I introduced a new struct used at executor time to pass to
ExecUpdate et al where they can install the various bits of status info
on its way out; this allowed cleanup of the function signatures, as well
as TM_FailureData which was being modified in a somewhat strange way.

I am not aware of anything of significance in terms of remaining work
for this project.  The one thing I'm a bit bothered about is the fact
that we expose a lot of executor functions previously static.  I am now
wondering if it would be better to move the MERGE executor support
functions into nodeModifyTable.c, which I think would mean we would not
have to expose those function prototypes.

-- 
Álvaro Herrera         PostgreSQL Developer  —  https://www.EnterpriseDB.com/

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.