Query performance question
- From: Mike Schmitt <mschmitt@xxxxxxxxxxxx>
- To: oracle-l@xxxxxxxxxxxxx
- Date: Thu, 02 Mar 2006 16:19:30 -0600
Hi All,
I was hoping someone could help me figure out a way to get better
performance from the following query. This is in a 10.2.0.1 instance with
updated statistics
This following query takes 6 minutes ~27million consistent gets:
select count(*) from fred.table_a A
where A.col_1 in (select col_3 from fred.table_b B where B.col_4 = '662')
or A.col_2 in (select col_3 from fas.table_b B where B.col_4 = '662')
If I make the above statement into two separate queries, each one takes
approximately 1 second.
for example:
1 second ~1400 consistent gets
select count(*) from fred.table_a A
where A.col_1 in (select col_3 from fred.table_b B where B.col_4 = '662')
..............................
I have tried using various hints, however my tracing keeps showing that the
statement with the 'or' continues to want to access table_A (which is
~7million rows) with a full table scan. While the individual queries
access table_A by way of indexes on col_1 and col_2.
Any ideas on how I can get the optimizer to handle this query differently,
and get the timing more in line with the individual queries.
Thanks in advance
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