Examples of org.apache.vxquery.compiler.rewriter.rules.ConsolidateUnnestsRule

org.apache.vxquery.compiler.rewriter.rules.ConsolidateUnnestsRule

The rule searches for an unnest operator (1) immediately following an unnest operator (2). XQuery unnest operator (1) must have a scalar implementation of the unnest function. If so the two unnest expressions can be merged together.

 Before  plan__parent UNNEST( $v2 : uf2( $v1 ) ) UNNEST( $v1 : uf1( $v0 ) ) plan__child Where $v1 is not used in plan__parent. After plan__parent UNNEST( $v2 : uf2( sf1( $v0 ) ) ) plan__child uf1 becomes sf1 since it changes from unnesting to scalar expression.

@author prestonc

        normalization.add(new SetCollectionDataSourceRule());
        normalization.add(new IntroduceCollectionRule());
        normalization.add(new RemoveUnusedAssignAndAggregateRule());


        // Adds child steps to the data source scan.
        normalization.add(new ConsolidateUnnestsRule());
        normalization.add(new PushChildIntoDataScanRule());


        // Improvement for scalar child expressions
        normalization.add(new EliminateSubplanForSingleItemsRule());
        return normalization;

        normalization.add(new SetCollectionDataSourceRule());
        normalization.add(new IntroduceCollectionRule());
        normalization.add(new RemoveUnusedAssignAndAggregateRule());


        // Adds child steps to the data source scan.
        normalization.add(new ConsolidateUnnestsRule());
        normalization.add(new PushChildIntoDataScanRule());


        // Improvement for scalar child expressions
        normalization.add(new EliminateSubplanForSingleItemsRule());
        return normalization;

Related Classes of org.apache.vxquery.compiler.rewriter.rules.ConsolidateUnnestsRule

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