Dynamic Query Operator Scheduling for Wide-Area Remote Access
Dynamic Query Operator Scheduling for Wide-Area Remote Access
Files
Publication or External Link
Date
1998-10-15
Authors
Amsaleg, Laurent
Franklin, Michael J.
Tomasic, Anthony
Advisor
Citation
DRUM DOI
Abstract
Distributed databases operating over wide-area networks such as the
Internet, must deal with the unpredictable nature of the performance
of communication. The response times of accessing remote sources can
vary widely due to network congestion, link failure, and other
problems. In such an unpredictable environment, the traditional iterator-based
query execution model performs poorly. We have developed a class of methods,
called query scrambling, for dealing explicitly with the problem of
unpredictable response times.
Query scrambling dynamically modifies query execution plans on-the-fly
in reaction to unexpected delays in data access. In this paper we focus on
the dynamic scheduling of query operators in the context of query scrambling.
We explore various choices for dynamic scheduling and examine, through a
detailed simulation, the effects of these choices. Our experimental
environment considers pipelined and non-pipelined join processing in a
client with multiple remote data sources and delayed or possibly bursty
arrivals of data. Our performance results show that scrambling rescheduling
is effective in hiding the impact of delays on query response time for a
number of different delay scenarios.
(Also cross-referenced as UMIACS- TR-97-54