Re: Adaptive query execution

[Tim Kane <tim.kane@xxxxxxxxx>]

From: Claudio Freire <klaussfreire@xxxxxxxxx>

I thought I would see what happens when I do this:

   SELECT * FROM ONLY table_a UNION SELECT * FROM table_b;

What's the point, in the context of this example?

The sort-unique still has to be performed even if you didn't have data

in one side, since the other could still have duplicates.

Damn it. Okay, bad example. I should sleep.

A better example would be (from my other post just now - http://www.postgresql.org/message-id/CF9838D8.7EF3D%tim.kane@xxxxxxxxx ) where an empty parent-table is append’ed into a result set involving one (and only one) of its child relations.  Whereas a more optimum solution would involve only the child relation without the need to append the empty parent relation.

I’m sure there are other scenarios where adaptive query execution would be of greater benefit.

Tim