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

Class RemoveUnusedSortDistinctNodesRule

java.lang.Object

org.apache.vxquery.compiler.rewriter.rules.RemoveUnusedSortDistinctNodesRule

All Implemented Interfaces:

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

public class RemoveUnusedSortDistinctNodesRule
extends Object
implements org.apache.hyracks.algebricks.core.rewriter.base.IAlgebraicRewriteRule

The rule searches for where the xquery sort distinct function is used and determines if the sort and distinct is necessary. The plan is modified if any of these items is not required.

 Before

   plan__parent
   ASSIGN( $v1 : sort_distinct_nodes_asc_or_atomics( $v0 ) )
   plan__child

   Where $v0 is a variable defined in plan__child.

 After

   if ( $v0 is unique nodes && $v0 is in document order )

     plan__parent
     ASSIGN( $v1 : $v0 )
     plan__child

   if ( $v0 is NOT unique nodes && $v0 is in document order )

     plan__parent
     ASSIGN( $v1 : distinct_nodes_or_atomics( $v0 ) )
     plan__child

   if ( $v0 is unique nodes && $v0 is NOT in document order )

     plan__parent
     ASSIGN( $v1 : sort_nodes_asc( $v0 ) )
     plan__child

   if ( $v0 is NOT unique nodes && $v0 is NOT in document order )

     plan__parent
     ASSIGN( $v1 : sort_distinct_nodes_asc_or_atomics( $v0 ) )
     plan__child
 

Author:

prestonc

Constructor Summary

Constructors

Constructor	Description
RemoveUnusedSortDistinctNodesRule()

Method Summary

Modifier and Type	Method	Description
boolean	rewritePost(org.apache.commons.lang3.mutable.Mutable<org.apache.hyracks.algebricks.core.algebra.base.ILogicalOperator> opRef, org.apache.hyracks.algebricks.core.algebra.base.IOptimizationContext context)
boolean	rewritePre(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 java.lang.Object

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

Constructor Detail

RemoveUnusedSortDistinctNodesRule

public RemoveUnusedSortDistinctNodesRule()

Method Detail

rewritePre

public boolean rewritePre(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:

rewritePre in interface org.apache.hyracks.algebricks.core.rewriter.base.IAlgebraicRewriteRule

Throws:

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

rewritePost

public boolean rewritePost(org.apache.commons.lang3.mutable.Mutable<org.apache.hyracks.algebricks.core.algebra.base.ILogicalOperator> opRef,
                           org.apache.hyracks.algebricks.core.algebra.base.IOptimizationContext context)

Specified by:

rewritePost in interface org.apache.hyracks.algebricks.core.rewriter.base.IAlgebraicRewriteRule