org.eigenbase.oj.rex
Class OJRexImplementorTableImpl.OJBasicAggImplementor

java.lang.Object
  org.eigenbase.oj.rex.OJRexImplementorTableImpl.OJBasicAggImplementor

All Implemented Interfaces:

OJAggImplementor

Direct Known Subclasses:

OJRexImplementorTableImpl.OJCountAggImplementor, OJRexImplementorTableImpl.OJMinMaxAggImplementor, OJRexImplementorTableImpl.OJSumAggImplementor

Enclosing class:

OJRexImplementorTableImpl

public abstract static class OJRexImplementorTableImpl.OJBasicAggImplementor
extends Object
implements OJAggImplementor

Constructor Summary

OJRexImplementorTableImpl.OJBasicAggImplementor()

Method Summary

boolean	canMerge() Returns whether this aggregation can merge together two accumulators.
void	implementMerge(JavaRelImplementor implementor, RelNode rel, Expression accumulator, Expression otherAccumulator) Generates (into the current statement list, gleaned by calling implementor's JavaRelImplementor.getStatementList() method) code to merge two accumulators.
Expression	implementStartAndNext(JavaRelImplementor implementor, JavaRel rel, AggregateCall call) This is a default implementation of OJAggImplementor.implementStartAndNext(org.eigenbase.oj.rel.JavaRelImplementor, org.eigenbase.oj.rel.JavaRel, org.eigenbase.rel.AggregateCall); particular derived classes may do better.

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.eigenbase.oj.rex.OJAggImplementor

implementNext, implementResult, implementStart

Constructor Detail

OJRexImplementorTableImpl.OJBasicAggImplementor

public OJRexImplementorTableImpl.OJBasicAggImplementor()

Method Detail

canMerge

public boolean canMerge()

Description copied from interface: OJAggImplementor

Returns whether this aggregation can merge together two accumulators.

For example, COUNT can (you just add the accumulators); AVG and MEDIAN cannot.

Specified by:

canMerge in interface OJAggImplementor

Returns:

whether this aggregation can merge together two accumulators

implementMerge

public void implementMerge(JavaRelImplementor implementor,
                           RelNode rel,
                           Expression accumulator,
                           Expression otherAccumulator)

Description copied from interface: OJAggImplementor

Generates (into the current statement list, gleaned by calling implementor's JavaRelImplementor.getStatementList() method) code to merge two accumulators. For sum(x), this looks like ((saffron.runtime.Holder.int_Holder) accumulator).value += ((saffron.runtime.Holder.int_Holder) other).value.

The method is only called if OJAggImplementor.canMerge() returns true.

Specified by:

implementMerge in interface OJAggImplementor

Parameters:

implementor - a callback object which knows how to generate things

rel - the relational expression which is generating this code

accumulator - the expression which holds the total

otherAccumulator - accumulator to merge in

implementStartAndNext

public Expression implementStartAndNext(JavaRelImplementor implementor,
                                        JavaRel rel,
                                        AggregateCall call)

This is a default implementation of OJAggImplementor.implementStartAndNext(org.eigenbase.oj.rel.JavaRelImplementor, org.eigenbase.oj.rel.JavaRel, org.eigenbase.rel.AggregateCall); particular derived classes may do better.

Specified by:

implementStartAndNext in interface OJAggImplementor