Oracle-L: Function Based Index

From: Prem Khanna J <jprem_at_kssnet.co.jp>
Date: Wed, 28 May 2003 22:54:50 -0800
Message-ID: <F001.005A537B.20030528225450@fatcity.com>

Guys,

create table Tab1 ( name varchar2(100),age int,state varchar2(100),country varchar2(100));

insert into tab1 values ('SCOTT',25,'TN','India');

I have 20,00,000 records like above.

create index idx1 on tab1 (upper(name));

analyze table tab1 compute statistics;
analyze index idx1 compute statistics;

select age from tab1 where upper(name)='SCOTT'; ---> this will return around 50 records.

0 SELECT STATEMENT Optimizer=CHOOSE (Cost=2458 Card=262146 Bytes=2097168) 1 0 TABLE ACCESS (FULL) OF 'TAB1' (Cost=2458 Card=262146 Bytes=2097168)

INIT.ORA ---------------------- optimizer_mode=choose compatible=8.1.0 query_rewrite_enabled=true query_rewrite_integrity=trusted
It's Oracle 8.1.6/Win2K.

When i add a HINT, IDX1 is used.Why is it so ? Why this SELECT does not use index IDX1 w/o a hint ?

TIA.
Jp.

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Author: Prem Khanna J
INET: jprem_at_kssnet.co.jp

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Function Based Index - Not Used ???