Scrambling Query Plans to Cope With Unexpected Delays
Scrambling Query Plans to Cope With Unexpected Delays
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Date
1998-10-15
Authors
Amsaleg, Laurent
Franklin, Michael J.
Tomasic, A.
Urhan., T.
Advisor
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Abstract
Accessing numerous widely-distributed data sources poses significant
new challenges for query optimization and execution. Congestion or
failure in the network introduce highly-variable response times for
wide-area data access. This paper is an initial exploration of
solutions to this variability. We investigate a class of dynamic,
run-time query plan modification techniques that we call query
plan scrambling. We present an algorithm which modifies execution
plans on-the-fly in response to unexpected delays in data
access. The algorithm both reschedules operators and
introduces new operators into the plan. We present simulation results
that show how our technique effectively hides delays in receiving
the initial requested tuples from remote data sources.
(Also cross-referenced as UMIACS-TR-96-35)