Design, Implementation, and Performance of the LHAM Log-Structured History Data Access Method
P. Muth, Patrick O’Neil, Achim Pick, Gerhard Weikum · 1998
Numerous applications such as stock market or medical informa-tion systems require that both historical and current data be logical-ly integrated into a temporal database. The underlying access method must support different forms of “time-travel ” queries, the migration of old record versions onto inexpensive archive media, and high insert and update rates. This paper introduces a new ac-cess method for transaction-time temporal data, called the Log-structured History Data Access Method (LHAM) that meets these demands. The basic principle of LHAM is to partition the data into successive components based on the timestamps of the record ver-sions. Components are assigned to different levels of a storage hier-archy, and incoming data is continuously migrated through the hierarchy. The paper discusses the LHAM concepts, including concurrency control and recovery, our full-fledged LHAM imple-mentation, and experimental performance results based on this im-plementation. A detailed comparison with the TSB-tree, both ana-lytically and based on experiments with real implementations, shows that LHAM is highly superior in terms of insert performance while query performance is in almost all cases at least as good as for the TSB-tree; in many cases it is much better, I