Banchong Harangsri

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We propose a new approach to the estimation of join selectivity. The technique, which we have called “systematic sampling”, is a novel variant of the sampling-based approach. Systematic sampling works as follows: Given a relation R of N tuples, with a join attribute that can be accessed in ascending/descending order via an index, if n is the number of(More)
In this paper, we propose a new approach to the estimation of query size for select and join operations. The technique, which we have called \systematic sam-pling", is a novel variant of the sampling approach, which sorts the relation before sampling, and which maintains a summary relation to improve run-time performance. We compare the method to a number(More)
Query optimisation is a signiicant unsolved problem in the development of multidatabase systems. The main reason for this is that the query cost functions for the component database systems may not be known to the global query optimiser. In this paper, we describe a method, based on a classical clustering algorithm, for classifying queries which allows us(More)
Query optimisation is a significant unsolved problem in the development of multidatabase systems. The main reason for this is that the query cost functions for the component database systems may not be known to the global query optimiser. In this paper, we describe a method, based on a classical clustering algorithm, for classifying queries which allows us(More)
In this paper, we propose a two-phase approach to the problem of optimal allocation of data objects (fragments) on a network in a distributed database system. In the rst phase, we perform fragment clustering 1 , in which we form groupings of fragments that tend to be accessed together. In the second phase, we use a \divide and con-quer" search technique to(More)
We propose a new approach to the estimation of query result sizes for join queries. The technique, which we have called “systematic sampling—SYSSMP”, is a novel variant of the sampling-based approach. A key novelty of the systematic sampling is that it exploits the sortedness of data; the result of this is that the sample relation obtained well represents(More)
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