Re: how to avoid fast full scan of index?

From: Anurag Varma <avarmadba.skipthis_at_yahoo.com>
Date: Fri, 08 Aug 2003 16:05:16 GMT
Message-ID: <0TPYa.268$aE1.186@nwrddc01.gnilink.net>

if you give a hint like

select /*+ index(g) */ .....

IMHO: it will avoid the fast full scan. Since it will override the index_ffs(g) clause.

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 - 11:05:16 CDT