Package org.apache.vxquery.compiler.rewriter.rules

Class ConsolidateUnnestsRule

java.lang.Object

org.apache.vxquery.compiler.rewriter.rules.AbstractUsedVariablesProcessingRule

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

All Implemented Interfaces:

org.apache.hyracks.algebricks.core.rewriter.base.IAlgebraicRewriteRule

public class ConsolidateUnnestsRule
extends AbstractUsedVariablesProcessingRule

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 and uf1 is not a descendant expression.
 
 After
 
   plan__parent
   UNNEST( $v2 : uf2( sf1( $v0 ) ) )
   plan__child
 
   uf1 becomes sf1 since it changes from unnesting to scalar expression.
 

Author:

prestonc

Field Summary

Fields inherited from class org.apache.vxquery.compiler.rewriter.rules.AbstractUsedVariablesProcessingRule

hasRun, usedVariables

Constructor Summary

Constructors

Constructor	Description
ConsolidateUnnestsRule()

Method Summary

Modifier and Type	Method	Description
protected boolean	processOperator(org.apache.commons.lang3.mutable.Mutable<org.apache.hyracks.algebricks.core.algebra.base.ILogicalOperator> opRef, org.apache.hyracks.algebricks.core.algebra.base.IOptimizationContext context)

Methods inherited from class org.apache.vxquery.compiler.rewriter.rules.AbstractUsedVariablesProcessingRule

rewritePost, rewritePre, rewritePreTrackingUsedVariables

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

ConsolidateUnnestsRule

public ConsolidateUnnestsRule()

Method Detail

processOperator

protected boolean processOperator(org.apache.commons.lang3.mutable.Mutable<org.apache.hyracks.algebricks.core.algebra.base.ILogicalOperator> opRef,
                                  org.apache.hyracks.algebricks.core.algebra.base.IOptimizationContext context)
                           throws org.apache.hyracks.algebricks.common.exceptions.AlgebricksException

Specified by:

processOperator in class AbstractUsedVariablesProcessingRule

Throws:

org.apache.hyracks.algebricks.common.exceptions.AlgebricksException