Re: Partial Analyze bad?

Unfortunately, the rule based optimizer will never use a full table scan if an index is available even if the full table scan would be much faster. I am seeing lots of these due to non-selective indexes in a third party application.

keith boulton wrote:

> On Thu, 25 Feb 1999 21:30:54 -0700, Ken Rachynski
> <krachyn_at_cadvision.com> wrote:
>
> >Good day,
> >
> >I was trying to analyze the tables in my application the other day and
> >had to stop the process with only half of the tables analyzed. Since
> >then, nearly all operations that use a mixture of analyzed and
> >non-analyzed tables slowed down considerably. I have removed all
> >statistics on my tables and the performance seems to have improved.
> >
> >Would I benefit much by having all the tables analyzed? Is it bad to
> >have only some analyzed?
>
> In general, you should analyse all or none of your tables.
> However, in version 7, the cost based optimiser has a very strong
> tendency to perform full table scans and hash joins in cases where it
> is very very much faster to use indexes and nested loops. This can be
> overcome by setting optimizer_mode = first_rows in your init.ora file.
Received on Sat Mar 06 1999 - 16:11:53 CST