Comments on: Cost – again http://jonathanlewis.wordpress.com/2011/01/10/cost-again/ Just another Oracle weblog Mon, 20 May 2013 17:10:14 +0000 hourly 1 http://wordpress.com/ By: Randolf Geist http://jonathanlewis.wordpress.com/2011/01/10/cost-again/#comment-39248 Fri, 21 Jan 2011 11:23:50 +0000 http://jonathanlewis.wordpress.com/?p=2227#comment-39248 This is a very valid point, and makes the whole point about “comparing costs of the same / different query” moot, in particular with the introduction of Cost Based Query Transformation (CBQT) in 10g – because since then the optimizer effectively compares costs of “different”, namely transformed, queries all the time (I assume this is what you intended to express with “it will also be comparing costs of different queries”).

It also gives an important clue why this improvement not always produces desirable results, simply because the cost estimates might be wrong for various reasons.

Randolf

]]> By: Doug's Oracle Blog http://jonathanlewis.wordpress.com/2011/01/10/cost-again/#comment-39220 Wed, 19 Jan 2011 00:00:50 +0000 http://jonathanlewis.wordpress.com/?p=2227#comment-39220 Cost…

As soon as I saw the title of Jonathan Lewis’ post, I had an inkling of what it might have to say and I wasn’t too far off the mark. Although I don’t disagree with a single statement of his post (I’ve read it a few times to make sure), I tend to ta…

]]>