From: Thomas Kellerer <spam_eater@gmx.net>
To: pgsql-performance@lists.postgresql.org
Subject: Re: Surprising benchmark count(1) vs. count(*)
Date: Thu, 19 Sep 2019 13:22:40 +0200
Message-ID: <35f81ca4-f68e-8b71-d34c-7364751b4e36@gmx.net> (raw)
In-Reply-To: <ab88db80f032933ff603d9d59745e8a09196bc1e.camel@cybertec.at>
References: <df354b76-a645-73fc-9645-4508e5291d71@gmx.net>
<ab88db80f032933ff603d9d59745e8a09196bc1e.camel@cybertec.at>
Laurenz Albe schrieb am 19.09.2019 um 12:22:
>> https://blog.jooq.org/2019/09/19/whats-faster-count-or-count1/
>>
>> Is there a reason why count(*) seems to be faster?
>
> "count(*)" is just the SQL standard's way of saying what you'd
> normally call "count()", that is, an aggregate without arguments.
>
> "count(1)" has to check if 1 IS NULL for each row, because NULL
> values are not counted. "count(*)" doesn't have to do that.
But 1 is a constant, why does it need to check it for each row?
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Subject: Re: Surprising benchmark count(1) vs. count(*)
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