On Fri, Jul 10, 2009 at 11:47 AM, Greg Stark<gsstark@mit.edu> wrote:
> On Fri, Jul 10, 2009 at 6:37 PM, Jeff Davis<pgsql@j-davis.com> wrote:
>>
>> -- foo has a primary key
>> SELECT * FROM foo UNION SELECT * FROM foo;
>>
>> That's logically equivalent to:
>>
>> SELECT * FROM foo;
>>
>> But postgresql will add a sort anyway.
>
>
> Well no, it's equivalent to SELECT DISTINCT * FROM foo;
And honestly, I'd rather see development effort go into making complex
queries run faster (the things like bitmap indexes on disk etc) rather
than optimising things that i can optimise myself.