Dynamic plan migration for snapshot-equivalent continuous queries in data stream systems

  • Authors:

  • Jürgen Krämer;Yin Yang;Michael Cammert;Bernhard Seeger;Dimitris Papadias

  • Affiliations:

  • University of Marburg, Germany;Hong Kong University of Science and Technology, China;University of Marburg, Germany;University of Marburg, Germany;Hong Kong University of Science and Technology, China

  • Venue:
  • EDBT'06 Proceedings of the 2006 international conference on Current Trends in Database Technology
  • Year:
  • 2006

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Abstract

A data stream management system executes a large number of continuous queries in parallel. As stream characteristics and query workload change over time, the plan initially installed for a continuous query may become inefficient. As a consequence, the query optimizer will re-optimize this plan based on the current statistics. The replacement of the running plan with a more efficient but semantically equivalent plan at runtime is called dynamic plan migration. In order to have a sound semantic foundation for query optimization, we investigate dynamic plan migration for snapshot-equivalent plans. We develop a general method for dynamic plan migration that treats the old and new plan as snapshot-equivalent black boxes. This enables the query optimizer to apply the conventional transformation rules during re-optimization. As a consequence, our approach supports the dynamic optimization of arbitrary continuous queries expressible in CQL, whereas existing solutions are limited in their scope.