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arXiv 1104.0867cs.DBcs.DS
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查询结果的分解表示

Factorised Representations of Query Results

Dan Olteanu, Jakub Zavodny

摘要:

查询易处理性传统上被定义为输入数据库和查询大小的函数,或者输入和输出大小的函数,其中查询结果被表示为元组包。在这份报告中,我们介绍了一个框架,允许调查超出此设置的易处理性。关键的见解是,虽然查询结果的基数可以是指数的,但它的结构可以是非常规则的,因此可以分解为嵌套表示,其大小仅是输入数据库和查询大小的多项式。对于一个给定的查询结果,可能有几个等价的表示,我们量化的结果的规则性,其可读性,这是最小的所有表示中的任何元组的最大出现次数表示。我们给出了一个特征的选择项目连接查询的基础上的任何输入数据库的结果的可读性的界限。我们补充它的算法,可以找到渐近最优的上限和相应的因式分解表示。

英文摘要:

Query tractability has been traditionally defined as a function of input database and query sizes, or of both input and output sizes, where the query result is represented as a bag of tuples. In this report, we introduce a framework that allows to investigate tractability beyond this setting. The key insight is that, although the cardinality of a query result can be exponential, its structure can be very regular and thus factorisable into a nested representation whose size is only polynomial in the size of both the input database and query. For a given query result, there may be several equivalent representations, and we quantify the regularity of the result by its readability, which is the minimum over all its representations of the maximum number of occurrences of any tuple in that representation. We give a characterisation of select-project-join queries based on the bounds on readability of their results for any input database. We complement it with an algorithm that can find asymptotically optimal upper bounds and corresponding factorised representations.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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