org.eigenbase.rel.rules
Class ReduceAggregatesRule

java.lang.Object
  org.eigenbase.relopt.RelOptRule
      org.eigenbase.rel.rules.ReduceAggregatesRule

public class ReduceAggregatesRule
extends RelOptRule

Rule to reduce aggregates to simpler forms. Currently only AVG(x) to SUM(x)/COUNT(x), but eventually will handle others such as STDDEV.

Version:

$Id: //open/dev/farrago/src/org/eigenbase/rel/rules/ReduceAggregatesRule.java#10 $

Author:

John V. Sichi

Field Summary

static ReduceAggregatesRule

instance The singleton.

Fields inherited from class org.eigenbase.relopt.RelOptRule

ANY, description, operands

Constructor Summary

protected

ReduceAggregatesRule(RelOptRuleOperand operand)

Method Summary

private RelDataType	getField(RelNode relNode, int i)
protected AggregateRelBase	newAggregateRel(AggregateRelBase oldAggRel, List<AggregateCall> newCalls) Do a shallow clone of oldAggRel and update aggCalls.
void	onMatch(RelOptRuleCall ruleCall) Receives notification about a rule match.
private void	reduceAverages(RelOptRuleCall ruleCall, AggregateRelBase oldAggRel)

Methods inherited from class org.eigenbase.relopt.RelOptRule

convert, equals, equals, getOperand, getOperands, getOutConvention, getOutTrait, hashCode, matches, mergeTraitsAndConvert, mergeTraitsAndConvert, toString

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Field Detail

instance

public static final ReduceAggregatesRule instance

The singleton.

Constructor Detail

ReduceAggregatesRule

protected ReduceAggregatesRule(RelOptRuleOperand operand)

Method Detail

onMatch

public void onMatch(RelOptRuleCall ruleCall)

Description copied from class: RelOptRule

Receives notification about a rule match. At the time that this method is called, call.rels holds the set of relational expressions which match the operands to the rule; call.rels[0] is the root expression.

Typically a rule would check that the nodes are valid matches, creates a new expression, then calls back RelOptRuleCall.transformTo(org.eigenbase.rel.RelNode) to register the expression.

Specified by:

onMatch in class RelOptRule

Parameters:

ruleCall - Rule call

See Also:

RelOptRule.matches(RelOptRuleCall)

reduceAverages

private void reduceAverages(RelOptRuleCall ruleCall,
                            AggregateRelBase oldAggRel)

newAggregateRel

protected AggregateRelBase newAggregateRel(AggregateRelBase oldAggRel,
                                           List<AggregateCall> newCalls)

Do a shallow clone of oldAggRel and update aggCalls. Could be refactored into AggregateRelBase and subclasses - but it's only needed for some subclasses.

Parameters:

oldAggRel - AggregateRel to clone.

newCalls - New list of AggregateCalls

Returns:

shallow clone with new list of AggregateCalls.

getField

private RelDataType getField(RelNode relNode,
                             int i)