Re: Huge speed penalty using <>TRUE instead of =FALSE

From: Peter Eisentraut <peter_e(at)gmx(dot)net>
To: pgsql-bugs(at)postgresql(dot)org
Cc: Mikael Krantz <mk(at)zigamorph(dot)se>, "Jan-Ivar Mellingen" <jan-ivar(dot)mellingen(at)alreg(dot)no>
Subject: Re: Huge speed penalty using <>TRUE instead of =FALSE
Date: 2009-07-17 12:35:29
Message-ID: 200907171535.29504.peter_e@gmx.net
Views: Raw Message | Whole Thread | Download mbox | Resend email
Thread:
Lists: pgsql-bugs

On Friday 17 July 2009 12:45:47 Mikael Krantz wrote:
> It might be that your column may be NULL as well as TRUE or FALSE. I
> am no expert in this matter though.

Nulls also need to be considered when attempting to substitute purportedly
equivalent clauses. But in this case it wouldn't actually matter, because

WHERE foo <> TRUE

and

WHERE foo = false

would both omit the row if foo is null. Both expressions only return true if
foo has the value "false". But again, this is data type specific knowledge.

In response to

Responses

Browse pgsql-bugs by date

  From Date Subject
Next Message Tom Lane 2009-07-17 14:11:49 Re: Huge speed penalty using <>TRUE instead of =FALSE
Previous Message Peter Eisentraut 2009-07-17 10:36:44 Re: Huge speed penalty using <>TRUE instead of =FALSE