org.apache.calcite.rel.rules

Class AggregateReduceFunctionsRule

java.lang.Object

org.apache.calcite.plan.RelOptRule

org.apache.calcite.rel.rules.AggregateReduceFunctionsRule

public class AggregateReduceFunctionsRule
extends org.apache.calcite.plan.RelOptRule

Planner rule that reduces aggregate functions in Aggregates to simpler forms.

Rewrites:

• AVG(x) → SUM(x) / COUNT(x)
• STDDEV_POP(x) → SQRT( (SUM(x * x) - SUM(x) * SUM(x) / COUNT(x)) / COUNT(x))
• STDDEV_SAMP(x) → SQRT( (SUM(x * x) - SUM(x) * SUM(x) / COUNT(x)) / CASE COUNT(x) WHEN 1 THEN NULL ELSE COUNT(x) - 1 END)
• VAR_POP(x) → (SUM(x * x) - SUM(x) * SUM(x) / COUNT(x)) / COUNT(x)
• VAR_SAMP(x) → (SUM(x * x) - SUM(x) * SUM(x) / COUNT(x)) / CASE COUNT(x) WHEN 1 THEN NULL ELSE COUNT(x) - 1 END

Since many of these rewrites introduce multiple occurrences of simpler forms like COUNT(x), the rule gathers common sub-expressions as it goes.

Field Summary

Fields

Modifier and Type	Field and Description
static AggregateReduceFunctionsRule	INSTANCE The singleton.

Fields inherited from class org.apache.calcite.plan.RelOptRule

description, operands, relBuilderFactory

Constructor Summary

Constructors

Constructor and Description
AggregateReduceFunctionsRule(org.apache.calcite.plan.RelOptRuleOperand operand, org.apache.calcite.tools.RelBuilderFactory relBuilderFactory) Creates an AggregateReduceFunctionsRule.

Method Summary

Modifier and Type	Method and Description
boolean	matches(org.apache.calcite.plan.RelOptRuleCall call)
protected void	newAggregateRel(org.apache.calcite.tools.RelBuilder relBuilder, org.apache.calcite.rel.core.Aggregate oldAggregate, List<org.apache.calcite.rel.core.AggregateCall> newCalls) Do a shallow clone of oldAggRel and update aggCalls.
protected void	newCalcRel(org.apache.calcite.tools.RelBuilder relBuilder, org.apache.calcite.rel.core.Aggregate oldAggregate, List<org.apache.calcite.rex.RexNode> exprs) Add a calc with the expressions to compute the original agg calls from the decomposed ones.
void	onMatch(org.apache.calcite.plan.RelOptRuleCall ruleCall)

Methods inherited from class org.apache.calcite.plan.RelOptRule

any, convert, convert, convertList, convertOperand, equals, equals, getOperand, getOperands, getOutConvention, getOutTrait, hashCode, none, operand, operand, operand, operand, operand, some, toString, unordered

Methods inherited from class java.lang.Object

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

Field Detail

INSTANCE

public static final AggregateReduceFunctionsRule INSTANCE

The singleton.

Constructor Detail

AggregateReduceFunctionsRule

public AggregateReduceFunctionsRule(org.apache.calcite.plan.RelOptRuleOperand operand,
                                    org.apache.calcite.tools.RelBuilderFactory relBuilderFactory)

Creates an AggregateReduceFunctionsRule.

Method Detail

matches

public boolean matches(org.apache.calcite.plan.RelOptRuleCall call)

Overrides:

matches in class org.apache.calcite.plan.RelOptRule

onMatch

public void onMatch(org.apache.calcite.plan.RelOptRuleCall ruleCall)

Specified by:

onMatch in class org.apache.calcite.plan.RelOptRule

newAggregateRel

protected void newAggregateRel(org.apache.calcite.tools.RelBuilder relBuilder,
                               org.apache.calcite.rel.core.Aggregate oldAggregate,
                               List<org.apache.calcite.rel.core.AggregateCall> newCalls)

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

Parameters:

relBuilder - Builder of relational expressions; at the top of its stack is its input

oldAggregate - LogicalAggregate to clone.

newCalls - New list of AggregateCalls

newCalcRel

protected void newCalcRel(org.apache.calcite.tools.RelBuilder relBuilder,
                          org.apache.calcite.rel.core.Aggregate oldAggregate,
                          List<org.apache.calcite.rex.RexNode> exprs)

Add a calc with the expressions to compute the original agg calls from the decomposed ones.

Parameters:

relBuilder - Builder of relational expressions; at the top of its stack is its input

oldAggregate - The original LogicalAggregate that is replaced.

exprs - The expressions to compute the original agg calls.