Horton

Re: support for MERGE

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

View thread View on postgr.es
From: Álvaro Herrera <alvherre@alvh.no-ip.org>
To: Zhihong Yu <zyu@yugabyte.com>
Cc: Andres Freund <andres@anarazel.de>, "pgsql-hackers@lists.postgresql.org" <pgsql-hackers@lists.postgresql.org>, Simon Riggs <simon.riggs@enterprisedb.com>, Tomas Vondra <tomas.vondra@enterprisedb.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: 2022-03-09T17:44:42Z
Lists: pgsql-hackers 
On 2022-Mar-07, Zhihong Yu wrote:

> For v13-0003-MERGE-SQL-Command-following-SQL-2016.patch :
> 
> +    * Reset per-tuple memory context to free any expression evaluation
> +    * storage allocated in the previous cycle.
> +    */
> +   ResetExprContext(econtext);
> 
> Why is the memory cleanup done in the next cycle ? Can the cleanup be done
> at the end of the current cycle ?

I have removed that, because Andres had already pointed out that it was
redundant with the reset done in the caller.

> +            * XXX Should this explain why MERGE has the same logic as UPDATE?
> 
> I think explanation should be given.

Actually, the routine in question is only handling insert, not UPDATE,
so MERGE is not relevant to the function.  I have removed the comment.
This was probably a leftover from work prior to 86dc90056dfd; that
commit made it all irrelevant.

-- 
Álvaro Herrera              Valdivia, Chile  —  https://www.EnterpriseDB.com/
"Ninguna manada de bestias tiene una voz tan horrible como la humana" (Orual)

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.