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Re: Minor mathematical error in documentation

From: Russell Smith <mr-russ(at)pws(dot)com(dot)au>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: pgsql-bugs(at)postgresql(dot)org
Subject: Re: Minor mathematical error in documentation
Date: 2008-01-18 08:59:42
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Lists: pgsql-bugs
Tom Lane wrote:
> Russell Smith <mr-russ(at)pws(dot)com(dot)au> writes:
>> In-equality transformations do not guarantee that y > 1.5x == y/x > 
>> 1.5.  This is only true for x>0, y < 1.5*x for x<0.  I have not posted a 
>> patch as I'm not sure what is the best way to change the example.
> Seems a bit nit-picky, but we could change the example to
I would agree, it's nit-picky.  But lots of people rely on the truth of 
the documentation.  People say I have any y/x > z situation, PostgreSQL 
manual says it works better if I do y > z*x.  So they do it, no 
questions asked. Which is the real fear from my point of view.
> SELECT ... WHERE x > 0 AND y/x > 1.5;
> becomes
> SELECT ... WHERE CASE WHEN x > 0 THEN y/x > 1.5 ELSE false END;
> 			regards, tom lane
> ---------------------------(end of broadcast)---------------------------
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