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

Class ConvertAssignToAggregateRule

java.lang.Object

org.apache.vxquery.compiler.rewriter.rules.AbstractVXQueryAggregateRule

org.apache.vxquery.compiler.rewriter.rules.ConvertAssignToAggregateRule

All Implemented Interfaces:

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

public class ConvertAssignToAggregateRule
extends AbstractVXQueryAggregateRule

The rule searches for assign operators that have a xquery aggregate function. The aggregate function will be more efficient when used by an aggregate operator. XQuery aggregate functions are implemented in both scalar (one XDM Instance input as a sequence) and iterative (a stream of XDM Instances each one is single object).

 Before
 
   plan__parent
   ASSIGN( $v2 : sf1( $v0 ) )
   plan__child
   
   Where sf1 is a XQuery aggregate function expression (count, max, min, 
   average, sum) with any supporting functions like treat, promote or data. 
   The variable $v0 is defined in plan__child.
   
 After
 
   plan__parent
   SUBPLAN{
     AGGREGATE( $v2 : af1( $v1 ) )
     UNNEST( $v1 : iterate( $v0 ) )
     NESTEDTUPLESOURCE
   }
   plan__child
 

Author:

prestonc

Constructor Summary

Constructors

Constructor	Description
ConvertAssignToAggregateRule()

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)	Find where an assign for a aggregate function is used before aggregate operator for a sequence.

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

getAggregateFunction

Methods inherited from class java.lang.Object

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

Constructor Detail

ConvertAssignToAggregateRule

public ConvertAssignToAggregateRule()

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

Find where an assign for a aggregate function is used before aggregate operator for a sequence. Search pattern 1: assign [function-call: count(function-call: treat($$))] Search pattern 2: $$ for aggregate [function-call: sequence()]

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)