Re: index fast full scan vs index range scan

From: Senthil Ramanujam <sramanujam_at_comcast.net>
Date: Sun, 21 Mar 2004 21:31:46 -0500
Message-ID: <405E5012.7000707@comcast.net>

Please ignore this message if this is a duplicate. I sent this immediately right after posting my message, but didnt make it i guess.

>>
Sorry...i just realized that i missed some relevant information.

Environment: 9.2.0.1, Solaris 8. i am using the default values for the init parameters, nothing really changed.

This table has got 1 million rows. The query in question uses a couple of other tables. It returns ~100 rows for a given value from this table. >>

Senthil Ramanujam wrote:

>
> List,
>
> I may need a little help here understanding Oracle optimization. How
> will the following code be treated in Oracle optimizer?
>
> table has a column called "code". code is (not null) varchar2(24). it
> has a regular index on this column. :b1 would have any valid value.
>
> * exec :b1 := 'xxx';
> ...
> select ... from ... where code like :b1 || '%'*
>
> the above code lets the optimizer to choose "index fast full scan".
> but changing the code slightly as given below:
>
> * exec :b1 := 'xxx' || '%';
> ...
> select ... from ... where code like :b1*
>
> lets the optimizer to choose "index range scan". obviously, the second
> method runs much faster.
>
> Any thoughts or inputs are much appreciated.
>
> thanks.
>
> senthil
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Received on Sun Mar 21 2004 - 20:28:44 CST