Re: cost based optimizer vs rule based optimizer

For large tables, you can save time by analyzing just a percentage of the table:

example: analyze table XXXXX estimate statistics sample 10 percent;

This should provide good statistics for CBO without taking the time to analyze the whole table.

mpir_at_compuserve.com wrote:

> A factor to consider is the size of the db and tables. I have some 50M row
> tables that are too large to analyze in our maintenance window(it takes too
> long, and they are needed for the user applications). FOr those apps, rule
> based is the only practical solution, at least until we can move the tables to
> partitions.
>
> In article <6mlpsq$c9c$1_at_nnrp1.dejanews.com>,
> alanlee1_at_my-dejanews.com wrote:
> >
> > CBO is normally the one to use but be careful with
> > query with self-join especially with huge tables.
> > If nothing works, try manual tuning with RBO.
> >
> > Hope this helps.
> >
> > Alan Lee
> > BSI
> >
> > In article <3576EE22.3AA6_at_creo.com>,
> > kbahi_at_creo.com wrote:
> > >
> > > Hi
> > > Does anyone have any opinions on which optimizer to use?
> > > Are they comparable? Is one always better than the other?
> > > Does it depend on the database ( volume, rate of change)
> > >
> > > Any info appreciated.
> > > BTW we are using oracle 8.0.3 under NT.
> > >
> > > Thanks
> > > Kel Bahi
> > > Creo Products
> > > kbahi_at_creo.com
> > >
> >
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>
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Received on Wed Jun 24 1998 - 00:00:00 CDT