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Optimization Algorithms for Exploiting the ParallelismCommunication Tradeoff in Pipelined Parallelism
, 1994
"... We address the problem of finding parallel plans for SQL queries using the twophase approach of join ordering followed by parallelization. We focus on the parallelization phase and develop algorithms for exploiting pipelined parallelism. We formulate parallelization as scheduling a weighted operato ..."
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Cited by 36 (2 self)
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We address the problem of finding parallel plans for SQL queries using the twophase approach of join ordering followed by parallelization. We focus on the parallelization phase and develop algorithms for exploiting pipelined parallelism. We formulate parallelization as scheduling a weighted operator tree to minimize response time. Our model of response time captures the fundamental tradeoff between parallel execution and its communication overhead. We assess the quality of an optimization algorithm by its performance ratio which is the ratio of the response time of the generated schedule to that of the optimal. We develop fast algorithms that produce nearoptimal schedules  the performance ratio is extremely close to 1 on the average and has a worst case bound of about 2 for many cases.
Scheduling Problems in Parallel Query Optimization
, 1995
"... We introduce a class of novel multiprocessor scheduling problems that arise in the optimization of SQL queries for parallel machines. These consist of scheduling a tree of interdependent communicating operators while exploiting both interoperator and intraoperator parallelism. We develop algorithm ..."
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Cited by 28 (1 self)
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We introduce a class of novel multiprocessor scheduling problems that arise in the optimization of SQL queries for parallel machines. These consist of scheduling a tree of interdependent communicating operators while exploiting both interoperator and intraoperator parallelism. We develop algorithms for the specific problem of scheduling a Pipelined Operator Tree in which all operators run in parallel using interoperator parallelism. Weights associated with nodes and edges represent respectively the cost of operators and communication. Communication cost is incurred only if adjacent operators are assigned different processors. The optimization problem is to assign operators to processors so as to minimize the maximum processor load. We develop two approximation algorithms for this NPhard problem. The faster algorithm has a performance ratio of 3.56 while the slower algorithm has a ratio of 2.87. 1 Introduction Exploiting parallel execution [DG92, Val93] to speed up database querie...
Scheduling and Mapping for Parallel Execution of Extended SQL Queries
 In ACM CIKM 95
, 1995
"... In this paper, we present an extension of PSA strategy (Parallel Scheduling Algorithm ), to determine an appropriate mapping of operations onto physical processors, taking into account the interconnection network topology of a sharednothing architecture. Performance evaluation, which relies on two b ..."
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Cited by 6 (1 self)
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In this paper, we present an extension of PSA strategy (Parallel Scheduling Algorithm ), to determine an appropriate mapping of operations onto physical processors, taking into account the interconnection network topology of a sharednothing architecture. Performance evaluation, which relies on two benchmarks shows the efficiency of PSA strategy by comparing to Static RightDeep strategy and to Bushy Tree Scheduling strategy. The major contributions of this work are (i) the incorporation of the mapping process into PSA strategy and (ii) the PSA strategy which provides a good tradeoff between response time minimization and throughput maximization. 1 Introduction The problem of ESQL [9] queries optimization for parallel execution is fundamental to obtain high performance and high data availability. One way to increase optimization capacity is to improve the efficiency of generating an optimal execution plan. The design of an ESQL queries Optimizer may be decomposed into three dimension...