Global query normalization to improve XML index based rewrites for path subsetted index
First Claim
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1. A method comprising:
- receiving a query that specifies a particular path expression;
normalizing the query to generate a normalized query, wherein normalizing the query comprises generating, based on the particular path expression, a plurality of normalized path expressions;
generating, based on the particular path expression, from a subset of the plurality of normalized path expressions, one or more temporary path expressions;
determining whether each of the one or more temporary path expressions is subsumed by a path of a node that is indexed by a path-subsetted XML index that is associated with one or more subsetted path expressions that indicate a set of one or more nodes that are indexed by said path-subsetted XML index; and
in response to determining that each of the one or more temporary path expressions is subsumed by a path of a node that is indexed by said path-subsetted XML index, using the path-subsetted XML index to process the plurality of normalized path expressions;
wherein the method is performed by one or more computers.
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Abstract
Techniques for processing a query that includes a path expression are provided. A query processor determines whether an XML index may be used to execute the query instead of having to scan multiple XML documents. The query is parsed and normalized, which results in multiple normalized path expressions that are based on the original path expression. If the XML index is a path-subsetted index, then the query processor generates annotated path expressions based on the normalized path expressions. The query processor determines whether each of the annotated path expressions is satisfiable by the path-subsetted XML index. If so, then the XML index is used to process the query.
173 Citations
18 Claims
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1. A method comprising:
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receiving a query that specifies a particular path expression; normalizing the query to generate a normalized query, wherein normalizing the query comprises generating, based on the particular path expression, a plurality of normalized path expressions; generating, based on the particular path expression, from a subset of the plurality of normalized path expressions, one or more temporary path expressions; determining whether each of the one or more temporary path expressions is subsumed by a path of a node that is indexed by a path-subsetted XML index that is associated with one or more subsetted path expressions that indicate a set of one or more nodes that are indexed by said path-subsetted XML index; and in response to determining that each of the one or more temporary path expressions is subsumed by a path of a node that is indexed by said path-subsetted XML index, using the path-subsetted XML index to process the plurality of normalized path expressions; wherein the method is performed by one or more computers. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. One or more non-transitory machine-readable media storing instructions which, when executed by one or more processors, cause:
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receiving a query that specifies a particular path expression; normalizing the query to generate a normalized query, wherein normalizing the query comprises generating, based on the particular path expression, a plurality of normalized path expressions generating, based on the particular path expression, from a subset of the plurality of normalized path expressions, one or more temporary path expressions; determining whether each of the one or more temporary path expressions is subsumed by a path of a node that is indexed by a path-subsetted XML index that is associated with one or more subsetted path expressions that indicate a set of one or more nodes that are indexed by said path-subsetted XML index; and in response to determining that each of the one or more temporary path expressions is subsumed by a path of a node that is indexed by said path-subsetted XML index, using the path-subsetted XML index to process the plurality of normalized path expressions. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18)
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Specification