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数据库管理系统概述英文版课件:tutorial10 Query Processing and Optimization.ppt
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数据库管理系统概述英文版课件:tutorial10 Query Processing and Optimization.ppt
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The Hong Kong
University of Science
and Technology
COMP231 Tutorial 10
Query Processing and Optimization
Department of Computer Science, HKUST2Database Management Systems
Review: Materialization and Pipelining
•
Materialization
•
Generate results of an expression whose inputs are relations
or the results are already computed, materialize (store) it on
disk.
•
Overall cost = Sum of costs of individual operations +
cost of writing intermediate results to disk
•
Pipelining
•
Pass tuples to parent operations immediately after an
operation is being executed
•
Avoid writing intermediate results to disk
Department of Computer Science, HKUST3Database Management Systems
•
Consider the relations R1(A,B,C), R2(C,D,E), and R3(E,F).
Primary keys are underlined and foreign keys in italics.
•
Assume that :
•
R1 has 1,000 tuples in 100 pages.
•
R2 has 10,000 tuples in 1,000 pages.
•
R3 has 100,000 tuples in 10,000 pages.
•
Give an efficient pipelining strategy to compute R1 R2 R3.
Exercise1: Index nested loop join and pipelining (1/3)
Department of Computer Science, HKUST4Database Management Systems
•
R1(A,B,C); 1,000 tuples; 100 pages.
•
R2(C,D,E); 10,000 tuples; 1,000 pages.
•
R3(E,F); 100,000 tuples;10,000 pages.
•
The size of the result is 1,000 tuples.
•
(R1 R2) R3 is cheaper than R1 (R2 R3), as is discussed
during the class.
Exercise1: Index nested loop join and pipelining (2/3)
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