Complete the implementation of XQuery Functions and Operators
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Key: VXQUERY-31
URL: https://issues.apache.org/jira/browse/VXQUERY-31
Project: VXQuery
Issue Type: Improvement
Reporter: Vinayak Borkar
VXQuery is an XQuery compiler and runtime being built to comply with version
1.0 of the XQuery spec at http://www.w3.org/TR/XQuery. The distinguishing
characteristic of this runtime is that it is designed to evaluate queries on
large amounts of XML data. VXQuery uses the Hyracks platform
(http://code.google.com/p/hyracks), a parallel dataflow engine, to parallelize
queries so they can run on a cluster of shared-nothing computers.
We plan to exploit three kinds of parallelism within the XQuery engine while
evaluating a single query.
1. Independent parallelism: Parts of a query that are unrelated to each other
can be evaluated in parallel.
2. Partitioned parallelism: The engine partitions data (both input data as well
as intermediate data) and processes the partitions in parallel.
3. Pipelined parallelism: The runtime organizes the work done to evaluate a
query as a sequence of workers. As and when work is completed on a piece of
data, the results of that piece are handed to the next worker, while the first
can process the next piece of data. This is similar to an assembly line used in
manufacturing plants.
Hyracks provides a set of operators to be able to evaluate queries in parallel.
However, it does not know anything about VXQuery or the XQuery language and
datamodel.
Currently we have a parser and translator that converts XQuery into a logical
form ready for evaluation.
The task that needs to be done as part of this project is to implement
functions that will plug into Hyracks operators so we can evaluate XQuery
queries.
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