Horton

Re: MERGE and parsing with prepared statements

Justin Pryzby <pryzby@telsasoft.com>

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From: Justin Pryzby <pryzby@telsasoft.com>
To: Alvaro Herrera <alvherre@alvh.no-ip.org>
Cc: Simon Riggs <simon.riggs@enterprisedb.com>, "David G. Johnston" <david.g.johnston@gmail.com>, Matthias van de Meent <boekewurm+postgres@gmail.com>, PostgreSQL Hackers <pgsql-hackers@postgresql.org>, Peter Eisentraut <peter.eisentraut@enterprisedb.com>, Amit Langote <amitlangote09@gmail.com>, Japin Li <japinli@hotmail.com>, Zhihong Yu <zyu@yugabyte.com>, PostgreSQL Developers <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: 2022-08-19T13:30:16Z
Lists: pgsql-hackers 
On Fri, Aug 12, 2022 at 01:53:25PM +0200, Alvaro Herrera wrote:
> On 2022-Aug-12, Simon Riggs wrote:
> 
> > Sorry, but I disagree with this chunk in the latest commit,
> > specifically, changing the MATCHED from after to before the NOT
> > MATCHED clause.

3d895bc84 also moved a semicolon into the middle of the sql statement.

> > The whole point of the second example was to demonstrate that the
> > order of the MATCHED/NOT MATCHED clauses made no difference.
> > 
> > By changing the examples so they are the same, the sentence at line
> > 573 now makes no sense.
> 
> Hmm, I thought the point of the example was to show that you can replace
> the table in the USING clause with a query that retrieves the column;
> but you're right, we lost the thing there.  Maybe it was too subtle to
> the point that I failed to understand it.  Perhaps we can put it back
> the way it was and explain these two differences (change of data source
> *and* clause ordering) more explicitly.

Evidently I misunderstood it, too.

-- 
Justin

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.