Re: MERGE ... WHEN NOT MATCHED BY SOURCE - Mailing list pgsql-hackers

On Sat, 1 Jul 2023 at 18:04, Dean Rasheed <dean.a.rasheed@gmail.com> wrote:
>
> On Tue, 21 Mar 2023 at 12:26, Alvaro Herrera <alvherre@alvh.no-ip.org> wrote:
> >
> > On 2023-Mar-21, Dean Rasheed wrote:
> >
> > > Looking at it with fresh eyes though, I realise that I could have just written
> > >
> > >     action->qual = make_and_qual((Node *) ntest, action->qual);
> > >
> > > which is equivalent, but more concise.
> >
> > Nice.
> >
> > I have no further observations about this patch.
> >
>
> Looking at this one afresh, it seems that the change to make Vars
> outer-join aware broke it -- the Var in the qual to test whether the
> source row is null needs to be marked as nullable by the join added by
> transform_MERGE_to_join(). That's something that needs to be done in
> transform_MERGE_to_join(), so it makes more sense to add the new qual
> there rather than in transformMergeStmt().
>
> Also, now that MERGE has ruleutils support, it's clear that adding the
> qual in transformMergeStmt() isn't right anyway, since it would then
> appear in the deparsed output.
>
> So attached is an updated patch doing that, which seems neater all
> round, since adding the qual is closely related to the join-type
> choice, which is now a decision taken entirely in
> transform_MERGE_to_join(). This requires a new "mergeSourceRelation"
> field on the Query structure, but as before, it does away with the
> "mergeUseOuterJoin" field.
>
> I've also updated the ruleutils support. In the absence of any WHEN
> NOT MATCHED BY SOURCE actions, this will output not-matched actions
> simply as "WHEN NOT MATCHED" for backwards compatibility, and to be
> SQL-standard-compliant. If there are any WHEN NOT MATCHED BY SOURCE
> actions though, I think it's preferable to output explicit "BY SOURCE"
> and "BY TARGET" qualifiers for all not-matched actions, to make the
> meaning clearer.

CFBot shows that the patch does not apply anymore as in [1]:
=== Applying patches on top of PostgreSQL commit ID
f2bf8fb04886e3ea82e7f7f86696ac78e06b7e60 ===
=== applying patch ./support-merge-when-not-matched-by-source-v8.patch
...
patching file doc/src/sgml/ref/merge.sgml
Hunk #5 FAILED at 409.
Hunk #9 FAILED at 673.
2 out of 9 hunks FAILED -- saving rejects to file
doc/src/sgml/ref/merge.sgml.rej
..
patching file src/include/nodes/parsenodes.h
Hunk #1 succeeded at 175 (offset -8 lines).
Hunk #2 succeeded at 1657 (offset -6 lines).
Hunk #3 succeeded at 1674 (offset -6 lines).
Hunk #4 FAILED at 1696.
1 out of 4 hunks FAILED -- saving rejects to file
src/include/nodes/parsenodes.h.rej

Please post an updated version for the same.

[1] - http://cfbot.cputube.org/patch_46_4092.log

Regards,
Vignesh