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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Thomas Munro <thomas.munro@gmail.com>
Cc: James Coleman <jtc331@gmail.com>
Cc: Tomas Vondra <tomas.vondra@2ndquadrant.com>
Cc: PostgreSQL mailing lists <pgsql-bugs@lists.postgresql.org>
Subject: Re: BUG #16104: Invalid DSA Memory Alloc Request in Parallel Hash
Date: Sun, 10 Nov 2019 16:34:09 -0500
Message-ID: <8966.1573421649@sss.pgh.pa.us> (raw)
In-Reply-To: <CA+hUKGLyafKXBMFqZCSeYikPbdYURbwr+jP6TAy8sY-8LO0V+Q@mail.gmail.com>
References: <CA+hUKGJUSbkivOxBqdN6dB9KoMxVZ-F8s28=Kr58cNMqKASktA@mail.gmail.com>
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	<20191109182735.ewficcv2hibbyzl4@development>
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	<20191110172925.mlkglpwzwego3wtp@development>
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	<CA+hUKGLyafKXBMFqZCSeYikPbdYURbwr+jP6TAy8sY-8LO0V+Q@mail.gmail.com>

Thomas Munro <thomas.munro@gmail.com> writes:
> I think I see what's happening: we're running out of hash bits.

Ugh.

> Besides switching to 64 bit hashes so that we don't run out of
> information (clearly a good idea), what other options do we have?

If the input column is less than 64 bits wide, this is an illusory
solution, because there can't really be that many independent hash bits.
I think we need to have some constraint that keeps us from widening
the batch+bucket counts to more hash bits than we have.

			regards, tom lane





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  Subject: Re: BUG #16104: Invalid DSA Memory Alloc Request in Parallel Hash
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