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In-Reply-To: <c2619b41-37da-4fed-99db-1444072771bd@vondra.me>
From: Amit Langote <amitlangote09@gmail.com>
Date: Fri, 23 May 2025 11:17:48 +0900
Message-ID: 
 <CA+HiwqGELoOkjV=5LhWm=x3GPE3=n0YP2sFuE_FEdrci1b+gqQ@mail.gmail.com>
Subject: Re: generic plans and "initial" pruning
To: Tomas Vondra <tomas@vondra.me>
Cc: Tom Lane <tgl@sss.pgh.pa.us>, Tender Wang <tndrwang@gmail.com>,
	Alexander Lakhin <exclusion@gmail.com>, Robert Haas <robertmhaas@gmail.com>,
	Alvaro Herrera <alvherre@alvh.no-ip.org>, Andres Freund <andres@anarazel.de>,
	Daniel Gustafsson <daniel@yesql.se>, David Rowley <dgrowleyml@gmail.com>,
	PostgreSQL Hackers <pgsql-hackers@postgresql.org>,
 Thom Brown <thom@linux.com>
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On Thu, May 22, 2025 at 10:04=E2=80=AFPM Tomas Vondra <tomas@vondra.me> wro=
te:
> On 5/22/25 10:12, Amit Langote wrote:
> > Note that I=E2=80=99ve only reverted the changes related to deferring l=
ocks on
> > prunable partitions. I=E2=80=99m planning to leave the preparatory comm=
its
> > leading up to that one in place unless anyone objects. For reference,
> > here they are in chronological order (the last 3 are bug fixes):
> >
> > bb3ec16e14d Move PartitionPruneInfo out of plan nodes into PlannedStmt
> > d47cbf474ec Perform runtime initial pruning outside ExecInitNode()
> > cbc127917e0 Track unpruned relids to avoid processing pruned relations
> > 75dfde13639 Fix an oversight in cbc127917 to handle MERGE correctly
> > cbb9086c9ef Fix bug in cbc127917 to handle nested Append correctly
> > 28317de723b Ensure first ModifyTable rel initialized if all are pruned
> >
> > I think separating initial pruning from plan node initialization is
> > still worthwhile on its own, as evidenced by the improvements in
> > cbc127917e.
> >
>
> I'm OK with that in principle, assuming the benefits outweigh the risk
> of making backpatching harder. The patches don't seem exceptionally
> large / invasive, but I don't know how often we modify these parts.

Thanks. I agree it's something to be mindful of, but I don=E2=80=99t expect
the reimplementation of the locking deferral to require changes to
this part of the code again. So barring any surprises, it shouldn't be
the case that the pruning code ends up looking significantly different
in v19.

Also, the actual pruning logic hasn=E2=80=99t changed much -- just where it=
=E2=80=99s
called from.

Let me know if any of that still raises concerns.

--=20
Thanks, Amit Langote