Re: how to avoid fast full scan of index?

> select /*+ index(g) */ .....
>
> IMHO: it will avoid the fast full scan. Since it will override the
> index_ffs(g) clause.

No, it will just tell CBO to use an index access path (fast full scan or skip scan for example).
There is an event: "10120 CBO Disable index fast full scan", but it didn't work in my test env (9.2.0.1 W2k).

Before I start speculating about optimizer_* parameters, it would be helpful to have both execution plans and your db version information. Also make sure, that your second join SQL is correct, not missing any predicates etc..

Tanel.

>
> Try that.
>
> Anurag
>
>
> "oofoof" <oofoofoof_at_ureach.com> wrote in message
> news:894b11eb.0308080802.65850337_at_posting.google.com...
> > I have a large query generated by a tool that joins tables
> > A-B-C-D-E-F-G-H-I
> > I modified the query to produce the same results by joining tables:
> > A-F-G-H-I
> >
> > A composite index is used by Oracle on table G in both queries, but in
> > the first case, Oracle uses an index range scan on that index while in
the
> > second case, Oracle uses a fast full scan on the same index. So, instead
> of
> > the second query running faster (joins fewer tables), it runs slower.
> > The query selects only a small subset of entries in the index and the
> index
> > has the 2 columns required to satisfy the query (no table access is
> necessary).
> > What can I do to avoid the fast full scan? I could not find a hint that
> > accomplished it. Will building a histogram on the index help?
>
>
Received on Fri Aug 08 2003 - 12:21:03 CDT