From: Tom Lane <tgl@sss.pgh.pa.us>
To: michalalbrycht@gmail.com
Cc: pgsql-bugs@lists.postgresql.org
Subject: Re: BUG #16840: Rows not found in table partitioned by hash when not all partitions exists
Date: Wed, 27 Jan 2021 13:08:34 -0500
Message-ID: <2407555.1611770914@sss.pgh.pa.us> (raw)
In-Reply-To: <16840-571a22976f829ad4@postgresql.org>
References: <16840-571a22976f829ad4@postgresql.org>
PG Bug reporting form <noreply@postgresql.org> writes:
> CREATE TABLE dir (
> id SERIAL,
> volume_id BIGINT,
> path TEXT
> ) PARTITION BY HASH (volume_id);
> CREATE TABLE dir_part_2 PARTITION OF dir FOR VALUES WITH (modulus 3,
> remainder 2);
> SELECT * FROM dir WHERE volume_id=1 AND (path='abc' OR path='def') --
> returns 0 rows - NOT OK!
Hmm, seems to be a case of faulty partition exclusion, because the
plan isn't scanning anything:
=# explain SELECT * FROM dir WHERE volume_id=1 AND (path='abc' OR path='def');
QUERY PLAN
------------------------------------------
Result (cost=0.00..0.00 rows=0 width=0)
One-Time Filter: false
(2 rows)
Probably the reason we'd not noticed is that an incomplete set of
hash partitions isn't a very useful situation: if you don't
populate all of the partitions, you risk unexpected insertion
failures, since you really shouldn't be assuming which partition
any given key value will map into. Still, it's clearly a bug.
Thanks for the report!
regards, tom lane
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To: pgsql-bugs@postgresql.org
Cc: tgl@sss.pgh.pa.us, michalalbrycht@gmail.com, pgsql-bugs@lists.postgresql.org
Subject: Re: BUG #16840: Rows not found in table partitioned by hash when not all partitions exists
In-Reply-To: <2407555.1611770914@sss.pgh.pa.us>
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