Optimization of real conjunctive queries

Optimization of real conjunctive queries
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真实连接查询的优化

DOI：
10.1145/153850.153856
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发表时间：
1993
期刊：
Proceedings of the twelfth ACM SIGACT-SIGMOD-SIGART symposium on Principles of database systems
影响因子：
--
通讯作者：
Moshe Y. Vardi
Moshe Y. Vardi
中科院分区：
--
文献类型：
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作者：
S. Chaudhuri;Moshe Y. Vardi

文献摘要

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合取查询的优化问题已经得到了广泛的研究。不幸的是，这项研究几乎总是假设集合论语义（即，删除重复项）。相反，SQL查询具有袋理论语义（即，通常不消除重复）。本文研究了Bagtheoretic语义下的合取查询优化问题。我们表明，从集理论设置的优化技术不结转袋理论设置。
The optimization problem for conjunctive queries has been studied extensively. Unfortunately, this research almost invariably assumes set-theoretic semantics (i.e., duplicates are eliminated). In contrast, SQL queries have bag-theoretic semantics (i.e., in general duplicates are not eliminated). In this paper we study the optimization problems for conjunct ive queries under bagtheoretic semantics. We show that optimization techniques from the set-theoretic setting do not carry over to the bag-theoretic setting.