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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Thomas Kellerer <spam_eater@gmx.net>
cc: pgsql-performance@lists.postgresql.org
Subject: Re: Surprising benchmark count(1) vs. count(*)
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Comments: In-reply-to Thomas Kellerer <spam_eater@gmx.net>
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Thomas Kellerer <spam_eater@gmx.net> writes:
> Laurenz Albe schrieb am 19.09.2019 um 12:22:
>> "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? 

[ shrug... ]  There's no special optimization for that case.
And I can't say that it seems attractive to add one.

			regards, tom lane