From: Tom Lane <tgl@sss.pgh.pa.us>
To: Alvaro Herrera <alvherre@2ndquadrant.com>
Cc: Pg Hackers <pgsql-hackers@lists.postgresql.org>
Subject: Re: weird hash plan cost, starting with pg10
Date: Mon, 23 Mar 2020 13:00:59 -0400
Message-ID: <18131.1584982859@sss.pgh.pa.us> (raw)
In-Reply-To: <20200323165059.GA24950@alvherre.pgsql>
References: <20200323165059.GA24950@alvherre.pgsql>
Alvaro Herrera <alvherre@2ndquadrant.com> writes:
> While messing with EXPLAIN on a query emitted by pg_dump, I noticed that
> current Postgres 10 emits weird bucket/batch/memory values for certain
> hash nodes:
> -> Hash (cost=0.11..0.11 rows=10 width=12) (actual time=0.002..0.002 rows=1 loops=8)
> Buckets: 2139062143 Batches: 2139062143 Memory Usage: 8971876904722400kB
> -> Function Scan on unnest init_1 (cost=0.01..0.11 rows=10 width=12) (actual time=0.001..0.001 rows=1 loops=8)
Looks suspiciously like uninitialized memory ...
> The complete query is:
Reproduces here, though oddly only a couple of the several hash subplans
are doing that.
I'm not planning to dig into it right this second either.
regards, tom lane
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To: pgsql-hackers@postgresql.org
Cc: tgl@sss.pgh.pa.us, alvherre@2ndquadrant.com, pgsql-hackers@lists.postgresql.org
Subject: Re: weird hash plan cost, starting with pg10
In-Reply-To: <18131.1584982859@sss.pgh.pa.us>
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