Subject: Re: Surprising benchmark count(1) vs. count(*)
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From: Thomas Kellerer <spam_eater@gmx.net>
To: pgsql-performance@lists.postgresql.org
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Date: Thu, 19 Sep 2019 13:22:40 +0200
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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?