Hi,
Wht is the purpose of ANALYZE command. if we ANALYZE the table/index wht happens to the object and how it improves the performance? Because why i am asking is, I have table which is contain fuction based index like UPPER(column_name). When i execute the below query, it is getting full table access.
select * from table_name where upper(column_name) = upper('ABC');
At the same time, when i analyze the table it is getting index based scan in the explain plan output.
ANALYZE TABLE table_name COMPUTE STATISTICS;
One more thing is when i execute DBMS_STATS package also the table is getting full table access. See my execute command below.
EXEC DBMS_STATS.gather_index_st
Can anyone share with me the solution of this? Thanks in advance.
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by: angelIIIPosted on 2009-01-28 at 23:49:25ID: 23494998
the analyse command will store statistics about the data in the table (and it's indexes) in the system, so that the analyser for your query execution, which determines the explain plan, knows more about what plan might be better.
it will however ignore (or put less weight) in outdates stats, hence after a ANALYSE command, it will consider it again, so give you a better plan again.