An efficient way to reestablish B+ trees in a distributed environment

Abstract

When a file is transferred from one site to another in a distributed environment, fast access paths supported by indices of the file like the B + tree at the sending site may become useless because of memory reallocation at the receiving site. It is known that (re-)establishing a B + tree at a receiving site is rather expensive. In this paper, we propose a method which allows us to obtain a data file and efficiently construct a similar B + tree on the file at a receiving site (the term similar is in the sense that both B + trees at the sending site and at the receiving site are indexed on the same attribute of the file, although they need not be identical) in a distributed environment. Both local processing cost and communication cost in terms of page I/Os are taken into consideration. We demonstrate that our approach is more cost-effective than the usual approach (which transfers the data file and then uses the data file to establish its B + index at the receiving site) despite a modest communication overhead. Under a typical situation, the usual approach is about 2 times more expensive than our approach in terms of page I/Os. Extensive performance study is also provided. The method is then generalized to situations where different sites may have different page sizes. Finally, the file reorganization problem is addressed, that is, useless data records such as empty records and records marked “deleted” in a file are not transferred, and a “fresh” file is established at the receiving site. File reorganization is also shown to be applicable to efficient database reloading and database reorganization.