RCached-tree: an index structure for efficiently answering popular queries

  • Authors:
  • Manash Pal;Arnab Bhattacharya;Debjyoti Paul

  • Affiliations:
  • Indian Institute of Technology, Kanpur, Kanpur, India;Indian Institute of Technology, Kanpur, Kanpur, India;Indian Institute of Technology, Kanpur, Kanpur, India

  • Venue:
  • Proceedings of the 22nd ACM international conference on Conference on information & knowledge management
  • Year:
  • 2013

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Abstract

In many applications of similarity searching in databases, a set of similar queries appear more frequently. Since it is rare that a query point with its associated parameters (range or number of nearest neighbors) will repeat exactly, intelligent caching mechanisms are required to efficiently answer such queries. In addition, the performance of non-repeating and non-cached queries should not suffer too much either. In this paper, we propose RCached-tree, belonging to the family of R-trees, that aims to solve this problem. In every internal node of the tree up to a certain level, a portion of the space is reserved for storing popular queries and their solutions. For a new query that is encompassed by a cached query, this enables bypassing the traversal of lower levels of the subtree corresponding to the node as the answers can be obtained directly from the result set of the cached query. The structure adapts itself to varying query patterns; new popular queries replace the old cached ones that are not popular any more. Queries that are not popular as well as insertions, deletions and updates are handled in the same manner as in a general R-tree. Experiments show that the RCached-tree can outperform R-tree and other such structures by a significant margin when the proportion of popular queries is 20% or more by reserving 30-40% of the internal nodes as cache.