Re: Microsoft destroys TPC-C records!

> >> Remember when we optimized queries by listing tables and conditions
> >> in a certain order in the FROM and WHERE clauses? Wasn't that "tuning"
> >> the query? Today, no one seems to mind that cost-based optimizers find
> >> the best execution path for our queries. In fact, we'd laugh at a
 

> > I seem to mind. While cost based optimization is great and works in most
> > cases, it does not always find the best execution path for our queries.
> > Thankfully I can go back to rule based queries whenever I want.
>
 

> With the rule-based approach, the optimizer chooses whether to use an access
> path based on these factors:
> o the available access paths for the statement
> o the ranks of these access paths
>
> To choose an access path, the optimizer first examines the conditions in the
> statemens WHERE clause to determine which access paths are available. The
> optimizer then chooses the most highly ranked available access path.
>
> Note that the full table scan is the lowest ranked access path on the list.
> This means that the rule-based approach always chooses an access path
> that uses an index if one is available,
> even if a full table scan might execute faster.

Out of ALL the comments I made in my last post, this is the only thing you could come back with? I'm well aware of the workings of rule based and cost based optimization. Maybe you've heard of a little thing called the EXPLAIN PLAN and it's companion, the HINT?!?! My point was that cost based optimization does not always choose the best path. It's nice to be able to use hints to change the path. I'd rather have that flexibility at my fingertips than to have the db make all the decisions for me. That's the point of the majority of my comments.

Thanks,
Brian

-- 
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Brian Peasland
Raytheons Systems at
  USGS EROS Data Center
These opinions are my own and do not
necessarily reflect the opinions of my 
company!
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