On applying hash filters to improving the execution of multi-join queries |
| |
Authors: | Ming-Syan Chen Hui-I Hsiao Philip S Yu |
| |
Affiliation: | (1) Electrical Engineering Department, National Taiwan University, Taipei, Taiwan , TW;(2) IBM T.J. Watson Research Center, P.O.Box 704, Yorktown, NY 10598, USA , US |
| |
Abstract: | In this paper, we explore an approach of interleaving a bushy execution tree with hash filters to improve the execution of
multi-join queries. Similar to semi-joins in distributed query processing, hash filters can be applied to eliminate non-matching
tuples from joining relations before the execution of a join, thus reducing the join cost. Note that hash filters built in
different execution stages of a bushy tree can have different costs and effects. The effect of hash filters is evaluat
ed first. Then, an efficient scheme to determine an effective sequence of hash filters for a bushy execution tree is developed,
where hash filters are built and applied based on the join sequence specified in the bushy tree so that not only is the reduction
effect optimized but also the cost associated is minimized. Various schemes using hash filters are implemented and evaluated
via simulation. It is experimentally shown that the application of hash filters is in general a very powerful means to improve
th
e execution of multi-join queries, and the improvement becomes more prominent as the number of relations in a query increases.
Edited by G. Gardarin. Received October 1994 / Accepted December 1995 |
| |
Keywords: | : Hash filters – Parallel query processing – Bushy trees – Sort-merge joins |
本文献已被 SpringerLink 等数据库收录! |
|