Re: support for MERGE

On Fri, Nov 12, 2021 at 9:58 AM Alvaro Herrera <alvherre@alvh.no-ip.org>
wrote:

> Here's a new version.  Many of the old complaints have been fixed;
> particularly, the handling of partitioned tables is now much cleaner and
> straightforward.  Amit Langote helped considerably in getting this part
> to shape -- thanks for that.  Amit also helped correct the EvalPlanQual
> behavior, which wasn't quite up to snuff.
>
> There are a few things that can still be improved here.  For one, I need
> to clean up the interactions with table AM (and thus heapam.c etc).
> Secondarily, and I'm now not sure that I really want to do it, is change
> the representation for executor: instead of creating a fake join between
> target and source, perhaps we should have just source, and give
> optimizer a separate query to fetch tuples from target.
>
> What I did do is change how the target table is represented from parse
> analysis to executor.  For example, in the original code, there were two
> RTEs that represented the target table; that is gone.  Now the target
> table is always just the query's resultRelation.  This removes a good
> number of ugly hacks that had been objected to.
>
> I'll park this in the January commitfest now.
>
> --
> Álvaro Herrera              Valdivia, Chile  —
> https://www.EnterpriseDB.com/
> "Cómo ponemos nuestros dedos en la arcilla del otro. Eso es la amistad;
> jugar
> al alfarero y ver qué formas se pueden sacar del otro" (C. Halloway en
> La Feria de las Tinieblas, R. Bradbury)
>
Hi,

+           skipped_path = total - insert_path - update_path - delete_path;

Should there be an assertion that skipped_path is not negative ?

+    * We maintain separate transaction tables for UPDATE/INSERT/DELETE
since
+    * MERGE can run all three actions in a single statement. Note that
UPDATE
+    * needs both old and new transition tables

Should the 'transaction' in the first line be transition ?

cheers