An evaluation between Bloom Filter join and PERF join in Distributed Query Processing

Nowadays, with the explosion of information and the telecommunication era\u27s coming, more and more huge applications encourage decentralization of data while accessing data from different sites [HFB00]. The process of retrieving data from different sites called Distributed Query Processing. The objective of distributed query optimization is to find the most cost-effective of executing query across the network [OV99]. Semijoin [BC81] [BG+81] is known as an effective operator to eliminate the tuples of a relation which are not contributive to a query. 2-way semijoin [KR87] is an extended version of semijoin which not only performs forward reduction like traditional semijoin does, but also provides backward reduction always in cost-effective way. Bloom Filter[B70] and PERF [LR95] are 2 filter based techniques which use a bit vector to represent of the original join attributes projection during the data transmission. Compare with generating a bit array with hash function in bloom filter, Perf join is based on the tuples scan order to avoid losing information caused by hash collision. In the thesis, we will apply both bloom filter and pert on 2-way semijoin algorithms to reduce transmission cost of distributed queries. Performance of propose algorithms will compare against each others and IFS (Initial Feasible Solution) through amount of experiments. \u27Keywords:\u27 Distributed Query Processing, Semijoin, Bloom Filter, Perf Join

An evaluation of PERF joins for a two-way semijoin based algorithm.

Distributed database system is becoming more widely used instead of centralized database systems in business world due to business expansion and network technology development. Query optimization provides a strategy for executing each query over the networks in the most cost-effective way, which aims to minimize the transmission cost over the networks. Many techniques and algorithms have been proposed to optimize queries, such as semijoin[BC81][BGW+81], 2-way semijoin[KR87], composite semijoin[PC90], hash semijoin[TC92], PERF join[LR95], etc. In distributed query processing, the semijoin has been used as an effective operator to reduce the total amount of data transmission. 2-way semijoin is an extended version of semijoin for more cost-effective distributed query processing. PERF joins are 2-way semijoins using a bit vector during the backward phase. PERF[LR95] is designed to minimize the cost of the backward reduction. It is based on the tuple scan order instead of hashing. Thus it does not suffer any loss of join information incurred by hash collisions. Algorithm UPSJ and Algorithm CPSJ are proposed based on a 2-way semijoin algorithm. Two variants of PERF joins are applied to the 2-way semijoin algorithm. In Algorithm UPSJ, uncompressed PERF joins and 2-way semijoin techniques are combined. In Algorithm CPSJ, compressed PERF joins are applied during the backward processing. Programs are designed to implement both original and the enhanced algorithms. Several experiments are conducted and the results showed a considerable enhancement obtained by applying the PERF join concept.Dept. of Computer Science. Paper copy at Leddy Library: Theses & Major Papers - Basement, West Bldg. / Call Number: Thesis2005 .Y36. Source: Masters Abstracts International, Volume: 44-03, page: 1419. Thesis (M.Sc.)--University of Windsor (Canada), 2005