On-the-fly tuple selection for XQuery

  • Authors:

  • Alexandru Berlea

  • Affiliations:

  • Technische Universität München

  • Venue:
  • XIME-P '07 Proceedings of the 4th international workshop on XQuery implementation, experience and perspectives
  • Year:
  • 2007

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Abstract

We address the problem of selection of fragments of XML input data as required for XQuery evaluation. Rather than first selecting individual fragments in isolation and then bringing them together as required by multiple variable bindings, we select the tuples of co-related fragments at once in one-pass over the input. Our approach is event-driven and correspondingly does not require building the input data in memory. The tuples as needed for generating the output are reported as early as possible. Combined with an incremental garbage collection scheme of the buffers, our approach allows to store at any time only as much data as necessarily needed for the query evaluation.