Bitmap index design and evaluation

  • Authors:

  • Chee-Yong Chan;Yannis E. Ioannidis

  • Affiliations:

  • Department of Computer Sciences, University of Wisconsin-Madison;Department of Informatics, University of Athens, Hellas (Greece) and Department of Computer Sciences, University of Wisconsin-Madison

  • Venue:
  • SIGMOD '98 Proceedings of the 1998 ACM SIGMOD international conference on Management of data
  • Year:
  • 1998

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Abstract

Bitmap indexing has been touted as a promising approach for processing complex adhoc queries in read-mostly environments, like those of decision support systems. Nevertheless, only few possible bitmap schemes have been proposed in the past and very little is known about the space-time tradeoff that they offer. In this paper, we present a general framework to study the design space of bitmap indexes for selection queries and examine the disk-space and time characteristics that the various alternative index choices offer. In particular, we draw a parallel between bitmap indexing and number representation in different number systems, and define a space of two orthogonal dimensions that captures a wide array of bitmap indexes, both old and new. Within that space, we identify (analytically or experimentally) the following interesting points: (1) the time-optimal bitmap index; (2) the space-optimal bitmap index; (3) the bitmap index with the optimal space-time tradeoff (knee); and (4) the time-optimal bitmap index under a given disk-space constraint. Finally, we examine the impact of bitmap compression and bitmap buffering on the space-time tradeoffs among those indexes. As part of this work, we also describe a bitmap-index-based evaluation algorithm for selection queries that represents an improvement over earlier proposals. We believe that this study offers a useful first set of guidelines for physical database design using bitmap indexes.