Horton

Re: MERGE ... RETURNING

Merlin Moncure <mmoncure@gmail.com>

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From: Merlin Moncure <mmoncure@gmail.com>
To: Jeff Davis <pgsql@j-davis.com>
Cc: Dean Rasheed <dean.a.rasheed@gmail.com>, Gurjeet Singh <gurjeet@singh.im>, Isaac Morland <isaac.morland@gmail.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Date: 2023-10-25T01:07:20Z
Lists: pgsql-hackers

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  1. Add RETURNING support to MERGE.

  2. doc: Improve a couple of places in the MERGE docs.

  3. doc: improve description of privileges for MERGE and update glossary.

  4. Fix RLS policy usage in MERGE.

  5. Fix leak of LLVM "fatal-on-oom" section counter.

  6. Implement outer-level aggregates to conform to the SQL spec, with

On Tue, Oct 24, 2023 at 2:11 PM Jeff Davis <pgsql@j-davis.com> wrote:

> On Wed, 2023-08-23 at 11:58 +0100, Dean Rasheed wrote:
> > Updated version attached, fixing an uninitialized-variable warning
> > from the cfbot.
>
> I took another look and I'm still not comfortable with the special
> IsMergeSupportFunction() functions. I don't object necessarily -- if
> someone else wants to commit it, they can -- but I don't plan to commit
> it in this form.
>
> Can we revisit the idea of a per-WHEN RETURNING clause? The returning
> clauses could be treated kind of like a UNION, which makes sense
> because it really is a union of different results (the returned tuples
> from an INSERT are different than the returned tuples from a DELETE).
> You can just add constants to the target lists to distinguish which
> WHEN clause they came from.
>
> I know you rejected that approach early on, but perhaps it's worth
> discussing further?
>

 Yeah.  Side benefit, the 'action_number' felt really out of place, and
that neatly might solve it.  It doesn't match tg_op, for example.  With the
current approach, return a text, or an enum? Why doesn't it match concepts
that are pretty well established elsewhere?  SQL has a pretty good track
record for not inventing weird numbers with no real meaning (sadly, not so
much the developers).   Having said that, pg_merge_action() doesn't feel
too bad if the syntax issues can be worked out.

Very supportive of the overall goal.

merlin