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

Class RemoveUnusedUnnestIterateRule

java.lang.Object

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

org.apache.vxquery.compiler.rewriter.rules.RemoveUnusedUnnestIterateRule

All Implemented Interfaces:

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

public class RemoveUnusedUnnestIterateRule
extends AbstractUsedVariablesProcessingRule

The rule searches for an unnest operator (1) immediately following an unnest or data scan operator (2). If the variable is only used in unnest (1) then unnest (1) can be removed.

 Before

   plan__parent
   UNNEST( $v2 : iterate( $v1 ) )
   UNNEST( $v1 : $v )
   plan__child

   Where $v1 is not used in plan__parent.

 After

   plan__parent
   ASSIGN( $v2 : $v1 )
   UNNEST( $v1 : $v )
   plan__child
 

Author:

prestonc

Field Summary

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

hasRun, usedVariables

Constructor Summary

Constructors

Constructor	Description
RemoveUnusedUnnestIterateRule()

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

RemoveUnusedUnnestIterateRule

public RemoveUnusedUnnestIterateRule()

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