Re: Cost based Query Vs Rule based query

David Slavin wrote:
>
> We recently received advanced Oracle training from an Oracle consultant
> who's been working in the industry for decades.
>
> He claimed that Rules based queries almost always outperform Cost based
> queries and he advised us to turn off the costing functions.
>
> To optimize query performance he recommended using EXPLAIN PLAN. In order
> to take advantage of EXPLAIN PLAN you have to know which basic functions
> allow for greater performance, and how reordering or changing your query
> will change the basic functions that Oracle chooses to implement your
> query. He was able to distill his years of experience into a basic list
> of do's and dont's.

My personal experience is that a competent individual can ***always*** create a rule-based statement that will outperform a cost-based statement - IF the individual is given the time & the mandate.

However, in a (what is becoming more typical) system that supports

1. A LOT of different queries
2. A LOT of individuals using ad-hoc tools without knowing how to use them
3. A LACK of competent individuals who have the time to do perf. analysis

cost-based optimization attempts to find a happy medium for everyone. This allows our few competent individuals the time to analyze and optimize the few statements that are indeed critical.

/Hans Received on Fri Feb 02 1996 - 00:00:00 CET