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Re: Attribute of type record has wrong type error with MERGE ... WHEN NOT MATCHED BY SOURCE THEN DELETE

Tom Lane <tgl@sss.pgh.pa.us>

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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Dean Rasheed <dean.a.rasheed@gmail.com>
Cc: Tender Wang <tndrwang@gmail.com>, Duncan Sands <duncan.sands@deepbluecap.com>, pgsql-bugs@lists.postgresql.org
Date: 2025-03-10T17:52:42Z
Lists: pgsql-bugs

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Dean Rasheed <dean.a.rasheed@gmail.com> writes:
> Unfortunately, it looks like this bug pre-dates MERGE WHEN NOT MATCHED
> BY SOURCE, and even MERGE itself. All that's needed to trigger it is a
> query that causes 2 whole-row Vars to be added, one before and one
> after view expansion. That can be made to happen via the rowmarking
> mechanism in all supported branches as follows:

Ugh, right.  So I withdraw my objection to fixing this in
makeWholeRowVar: all of the post-rewrite calls have need for this
behavior.  However, the proposed code change is wrong in detail.
The existing places that are checking for this situation are doing
tests like
	(rte->rtekind == RTE_SUBQUERY && OidIsValid(rte->relid)))
I don't believe that checking relkind instead is an improvement.

> Reading the commit message for 47bb9db7599 suggests that maybe it
> would be OK to further back-patch the changes to ApplyRetrieveRule()
> to retain relkind and relid on subquery RTEs for this purpose. That
> wouldn't affect stored rules, but I haven't looked to see what else it
> might affect.

Yeah, I think we can likely get away with that.  We cannot back-patch
the changes that added relid to the outfuncs/readfuncs representation,
which means that the RTE's relid won't propagate to parallel workers,
but I don't see why they'd need it.  We only need that info to get
as far as planning.  I've not tried though.

Draft HEAD patch attached.

			regards, tom lane

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Repair commits 317aba70e et al for -DWRITE_READ_PARSE_PLAN_TREES.

  2. Build whole-row Vars the same way during parsing and planning.

  3. Preserve RangeTblEntry.relid when expanding a view RTE.

  4. Fix incorrect non-strict join recheck in MERGE WHEN NOT MATCHED BY SOURCE.