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Re: Optimizer Question [message #18340] Mon, 28 January 2002 09:38
andrew again
Messages: 2577
Registered: March 2000
Senior Member
Do a warm query. i.e. don't measure the time for the first execution of the query. Run them both twice.

Also - check the gathered stats on the tables. If Oracle thinks there are only a few rows in the table it may decide not to use the index, whereas you may have tons of records.

select table_name, num_rows, last_analyzed from user_tables where table_name = ...;
select table_name, index_name, num_rows, last_analyzed from user_indexes where table_name = ...;

compare that to select count(*) from ...;

Analyze table ... estimate statistics;
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