Sami,
Your problem is not with the index, but rather the cost based optimizer. Most
of us have been beat severely over the head and shoulders through the years that full
table scans are a BAD thing, me included BTW. Well, it's time for the old dog to
learn new tricks. So that I'm not a long winded person, take a look in Select
magazine, 3rd qtr 2003, for the article "In Defense of Full Table Scans" by Jeff
Maresh. For a long time the CBO was a mystery to me as well especially when it did
unexpected things like this. I've applied Jeff's ideas on computing an index's
efficiency to see if it explained what the CBO did. Amazingly in 95% of the cases
I've analyzed it made absolute sense.
I'm including Jeff with a courtesy copy of this message so that 1) I can pat
him for making the waters clear and 2) so he can add anything he desires.
Dick Goulet
Senior Oracle DBA
Oracle Certified 8i DBA
-----Original Message-----
Sent: Wednesday, November 05, 2003 12:10 PM
To: Multiple recipients of list ORACLE-L
Hi List,
Does someone throw ligts on the following index behavior
Note
a)"name" is an unique index column
b) table and index has been analyzed b4 running the query
1) select id from table1 where name like 'ABC%';
FULL Table scan
1) select id from table1 where name like 'AB%';
Index scan
"name" is an unique index column
Any help would be really appreciated.
-Sami
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