From: Tom Lane <tgl@sss.pgh.pa.us>
To: Justin Pryzby <pryzby@telsasoft.com>
cc: Alvaro Herrera <alvherre@alvh.no-ip.org>, pgsql-hackers@postgresql.org,
        Amit Langote <amitlangote09@gmail.com>
Subject: Re: \d with triggers: more than one row returned by a subquery used as an expression
In-reply-to: <20211222210308.GD17618@telsasoft.com>
References: <20211217154356.GJ17618@telsasoft.com> <20211222210308.GD17618@telsasoft.com>
Comments: In-reply-to Justin Pryzby <pryzby@telsasoft.com>
	message dated "Wed, 22 Dec 2021 15:03:08 -0600"
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Date: Mon, 17 Jan 2022 17:02:00 -0500
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Justin Pryzby <pryzby@telsasoft.com> writes:
> On Fri, Dec 17, 2021 at 09:43:56AM -0600, Justin Pryzby wrote:
>> I want to mention that the 2nd problem I mentioned here is still broken=
.
>> https://www.postgresql.org/message-id/20210717010259.GU20208@telsasoft.=
com
>> It happens if non-inheritted triggers on child and parent have the same=
 name.

> This is the fix I was proposing
> It depends on pg_partition_ancestors() to return its partitions in order=
:
> this partition =3D> parent =3D> ... =3D> root.

I don't think that works at all.  I might be willing to accept the
assumption about pg_partition_ancestors()'s behavior, but you're also
making an assumption about how the output of pg_partition_ancestors()
is joined to "pg_trigger AS u", and I really don't think that's safe.

ISTM the real problem is the assumption that only related triggers could
share a tgname, which evidently isn't true.  I think this query needs to
actually match on tgparentid, rather than taking shortcuts.  If we don't
want to use a recursive CTE, maybe we could define it as only looking up
to the immediate parent, rather than necessarily finding the root?

			regards, tom lane