Re: generic plans and "initial" pruning

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From: Tender Wang <[email protected]>
To: Amit Langote <[email protected]>
Cc: Alexander Lakhin <[email protected]>
Cc: Tomas Vondra <[email protected]>
Cc: Robert Haas <[email protected]>
Cc: Alvaro Herrera <[email protected]>
Cc: Andres Freund <[email protected]>
Cc: Daniel Gustafsson <[email protected]>
Cc: David Rowley <[email protected]>
Cc: PostgreSQL Hackers <[email protected]>
Cc: Thom Brown <[email protected]>
Cc: Tom Lane <[email protected]>
Subject: Re: generic plans and "initial" pruning
Date: Sun, 23 Feb 2025 20:46:03 +0800
Message-ID: <CAHewXNkUz9XGG8nnoxZaw35e+5bQVVP=eeJE4cW4V2e+P9ndFw@mail.gmail.com> (raw)
In-Reply-To: <CA+HiwqFp3jZGSz==QjeuV62_62F6+V6b62=Uqvy99sW_gsgWBA@mail.gmail.com>
References: <CA+HiwqFpZ80UJKr4tZus4Omgg7YESzFXKSwSHRW2Ap2=XSVyUA@mail.gmail.com>
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Amit Langote <[email protected]> 于2025年2月23日周日 16:36写道：

> On Sun, Feb 23, 2025 at 2:03 AM Tender Wang <[email protected]> wrote:
> > Alexander Lakhin <[email protected]> 于2025年2月22日周六 23:00写道：
> >> 21.02.2025 05:40, Amit Langote wrote:
> >>
> >> I pushed the final piece yesterday.
> >>
> >>
> >> Please look at new error, produced by the following script,
> >> starting from 525392d57:
> >> CREATE TABLE t(id int) PARTITION BY RANGE (id);
> >> CREATE INDEX idx on t(id);
> >> CREATE TABLE tp_1 PARTITION OF t FOR VALUES FROM (10) TO (20);
> >> CREATE TABLE tp_2 PARTITION OF t FOR VALUES FROM (20) TO (30) PARTITION
> BY RANGE(id);
> >> CREATE TABLE tp_2_1 PARTITION OF tp_2 FOR VALUES FROM (21) to (22);
> >> CREATE TABLE tp_2_2 PARTITION OF tp_2 FOR VALUES FROM (22) to (23);
> >> CREATE FUNCTION stable_one() RETURNS INT AS $$ BEGIN RETURN 1; END; $$
> LANGUAGE plpgsql STABLE;
> >>
> >> SELECT min(id) OVER (PARTITION BY id ORDER BY id) FROM t WHERE id >=
> stable_one();
> >>
> >> ERROR:  XX000: trying to open a pruned relation
> >> LOCATION:  ExecGetRangeTableRelation, execUtils.c:830
> >>
> >> This issue was discovered with SQLsmith.
>
> Thanks for the report.
>
> > The error message was added in commit  525392d57. In this case, the
> estate->es_unpruned_relids only includes 1, which is the offset of table t.
> > In register_partpruneinfo(), we collect glob->prunableRelids; in this
> case, it contains 2,3,4,5. Then we will do:
> > result->unprunableRelids = bms_difference(glob->allRelids,
> >  glob->prunableRelids);
> > so the result->unprunableRelids only contains 1.
> >
> > But tp_2 is also partition table, and its partpruneinfo created by
> create_append_plan() is put into the head of global list.
> > So we first process it in ExecDoInitialPruning().  Then error reports
> because we only contain 1 in estate->es_unpruned_relids.
>
> Thanks for checking.
>
> The RT index of tp_2 should appear in PlannedStmt.unprunableRelids,
> because it needs to be opened in CreatePartitionPruneState() for
> setting up its PartitionPruneInfo. We use ExecGetRangeTableRelation()
> to open, which expects the relation to be locked, so the error.
>
> To ensure tp_2 appears in PlannedStmt.unprunableRelids, we should
> prevent make_partitionedrel_pruneinfo() from placing the RT index into
> leafpart_rti_map[], as the current condition for inclusion doesn’t
> account for whether the partition is itself partitioned.
>
> I've come up with the attached.
>

LGTM.

-- 
Thanks,
Tender Wang

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