From: Tom Lane <tgl@sss.pgh.pa.us>
To: Richard Guo <guofenglinux@gmail.com>
cc: Konstantin Knizhnik <k.knizhnik@postgrespro.ru>,
        Thomas Munro <thomas.munro@gmail.com>,
        Alvaro Herrera <alvherre@2ndquadrant.com>,
        Pg Hackers <pgsql-hackers@lists.postgresql.org>
Subject: Re: weird hash plan cost, starting with pg10
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Comments: In-reply-to Richard Guo <guofenglinux@gmail.com>
	message dated "Mon, 13 Apr 2020 17:07:41 +0800"
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Date: Mon, 13 Apr 2020 09:53:46 -0400
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Richard Guo <guofenglinux@gmail.com> writes:
> At first I was wondering if we need to check whether HashState.hashtable
> is not NULL in ExecShutdownHash() before we decide to allocate save
> space for HashState.hinstrument. And then I convinced myself that that's
> not necessary since HashState.hinstrument and HashState.hashtable cannot
> be both NULL there.

Even if the hashtable is null at that point, creating an all-zeroes
hinstrument struct is harmless.

			regards, tom lane