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From: David Rowley <dgrowleyml@gmail.com>
Date: Fri, 1 Apr 2022 21:19:49 +1300
Message-ID: <CAApHDvqno9XyXr9aXyWOKQ96-fzdyh5dRZbbzTQopYNq1CNJCQ@mail.gmail.com>
Subject: Re: generic plans and "initial" pruning
To: Amit Langote <amitlangote09@gmail.com>
Cc: Robert Haas <robertmhaas@gmail.com>, Tom Lane <tgl@sss.pgh.pa.us>, 
	PostgreSQL-development <pgsql-hackers@postgresql.org>
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On Fri, 1 Apr 2022 at 19:58, Amit Langote <amitlangote09@gmail.com> wrote:
> Yes, the ExecLockRelsInfo node in the current patch, that first gets
> added to the QueryDesc and subsequently to the EState of the query,
> serves as that stashing place.  Not sure if you've looked at
> ExecLockRelInfo in detail in your review of the patch so far, but it
> carries the initial pruning result in what are called
> PlanInitPruningOutput nodes, which are stored in a list in
> ExecLockRelsInfo and their offsets in the list are in turn stored in
> an adjacent array that contains an element for every plan node in the
> tree.  If we go with a PlannedStmt.partpruneinfos list, then maybe we
> don't need to have that array, because the Append/MergeAppend nodes
> would be carrying those offsets by themselves.

I saw it, just not in great detail. I saw that you had an array that
was indexed by the plan node's ID.  I thought that wouldn't be so good
with large complex plans that we often get with partitioning
workloads.  That's why I mentioned using another index that you store
in Append/MergeAppend that starts at 0 and increments by 1 for each
node that has a PartitionPruneInfo made for it during create_plan.

> Maybe a different name for ExecLockRelsInfo would be better?
>
> Also, given Tom's apparent dislike for carrying that in PlannedStmt,
> maybe the way I have it now is fine?

I think if you change how it's indexed and the other stuff then we can
have another look.  I think the patch will be much easier to review
once the ParitionPruneInfos are moved into PlannedStmt.

David