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Netezza Balanced optimizer adds order by clause

Posted: Thu Mar 21, 2013 12:20 am
by wbeitler
Hi all,

when using the balanced optimizer for Netezza, the join stages being pushed back to the source database, are combined in a single query
as planned. For some reason there is an order by clause added on the join key columns.

This order by slows down query performance big time, so question is how to make balanced optimizer loose the urge to create the order by clause...

Not keen on changing the optimized jobs after they are being created, for obvious reasons...

thanks,

William

Posted: Thu Mar 21, 2013 3:14 pm
by PaulVL
Odd, I was thinking that I would not accept the auto generated job at face value for the same obvious reasons.

Letting a tool do it all is nice for the most part, but you still have to eyeball the end result. Should something logically work better a different way, then tweek it.

The tools will rarely dive deep into your data to understand the impact the order by clause could have. Is it a good idea to put in? conceptually yes. Best idea under every circomstance... you decide.