Tuning Query w/database link
- From: "Hostetter, Jay M" <JHostetter@xxxxxxxxxxxxxxxxxxxx>
- To: <oracle-l@xxxxxxxxxxxxx>
- Date: Fri, 6 Aug 2004 15:31:59 -0400
I am trying to help a developer tune a query that uses a database link.
For testing purposes, I've broken the query down to the simple query
shown below. TEST_VIEW is a remote view that joins three tables, which
results in approximately 1 million rows. The query that Oracle passes
to the remote database never has a predicate - it is always 'select *
from test_view'. I have tried various hints, but I cannot get Oracle to
use a predicate in the remote query. The user has to wait 6 minutes (or
so) while the remote query pulls 1 million records to the local
database. If I execute an explain plan for 'select * from test_view
where a.alra_id=100001', an index is used an the query completes in
milliseconds. Any thoughts on how I can help this user, without
creating local snapshots of the tables?
select * from test_view@remotenode <mailto:j@remotenode> a,
project_accounting_costs b
where a.alra_id=b.source_id
and b.source_id=100001;
Both databases are 8.1.7.3 on Tru64. Both databases have statistics
computed and the optimizer_mode=CHOOSE. I've tried various hints
including DRIVING_SITE, FIRST_ROWS, ALL_ROWS, INDEX, etc. I also put a
hint in the remote view.
Thanks,
Jay
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