Horton

Re: support for MERGE

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

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From: Álvaro Herrera <alvherre@alvh.no-ip.org>
To: "Andres Freund" <andres@anarazel.de>
Cc: "pgsql-hackers@lists.postgresql.org" <pgsql-hackers@lists.postgresql.org>, "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: 2022-03-07T20:04:01Z
Lists: pgsql-hackers 
On Mon, Mar 7, 2022, at 4:59 PM, Álvaro Herrera wrote:
> I attach v13 here.  This version includes a 0002 that's does the split of nodeModifyTable.c routines, then 0003 implements MERGE on top of that.  0001 is as before.

In 0002, I've opted to have two separate structs.  One is the ModifyTableContext, as before, but I've removed 'tupleid' and 'oldtuple' (the specification of the tuple to delete/update) because it makes ExecCrossPartitionUpdate cleaner if we pass them separately.  The second struct is UpdateContext, which is used inside ExecUpdate as output data from its subroutines.  This is also for the benefit of cross-partition updates.

I'm pretty happy with how this turned out; even without considering MERGE, it seems to me that ExecUpdate benefits from being shorter.

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.