org.apache.calcite.rel.rules

Class AggregateReduceFunctionsRule

java.lang.Object

org.apache.calcite.plan.RelOptRule

org.apache.calcite.plan.RelRule<AggregateReduceFunctionsRule.Config>

org.apache.calcite.rel.rules.AggregateReduceFunctionsRule

All Implemented Interfaces:

TransformationRule

@Value.Enclosing
public class AggregateReduceFunctionsRule
extends RelRule<AggregateReduceFunctionsRule.Config>
implements TransformationRule

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
• COVAR_POP(x, y) → (SUM(x * y) - SUM(x, y) * SUM(y, x) / REGR_COUNT(x, y)) / REGR_COUNT(x, y)
• COVAR_SAMP(x, y) → (SUM(x * y) - SUM(x, y) * SUM(y, x) / REGR_COUNT(x, y)) / CASE REGR_COUNT(x, y) WHEN 1 THEN NULL ELSE REGR_COUNT(x, y) - 1 END
• REGR_SXX(x, y) → REGR_COUNT(x, y) * VAR_POP(y)
• REGR_SYY(x, y) → REGR_COUNT(x, y) * VAR_POP(x)

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

See Also:

CoreRules.AGGREGATE_REDUCE_FUNCTIONS

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static interface	AggregateReduceFunctionsRule.Config Rule configuration.

Nested classes/interfaces inherited from class org.apache.calcite.plan.RelRule

RelRule.Done, RelRule.MatchHandler<R extends RelOptRule>, RelRule.OperandBuilder, RelRule.OperandDetailBuilder<R extends RelNode>, RelRule.OperandTransform

Nested classes/interfaces inherited from class org.apache.calcite.plan.RelOptRule

RelOptRule.ConverterRelOptRuleOperand

Field Summary

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

config

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

description, operands, relBuilderFactory

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	AggregateReduceFunctionsRule(AggregateReduceFunctionsRule.Config config) Creates an AggregateReduceFunctionsRule.
	AggregateReduceFunctionsRule(Class<? extends Aggregate> aggregateClass, RelBuilderFactory relBuilderFactory, EnumSet<SqlKind> functionsToReduce) Deprecated.
	AggregateReduceFunctionsRule(RelOptRuleOperand operand, RelBuilderFactory relBuilderFactory) Deprecated.

Method Summary

Modifier and Type	Method and Description
boolean	canReduce(AggregateCall call) Returns whether this rule can reduce a given aggregate function call.
boolean	canReduceAggCallByGrouping(Aggregate oldAggRel, AggregateCall call) Returns whether this rule can reduce some agg-call, which its arg exists in the aggregate's group.
boolean	matches(RelOptRuleCall call) Returns whether this rule could possibly match the given operands.
protected void	newAggregateRel(RelBuilder relBuilder, Aggregate oldAggregate, List<AggregateCall> newCalls) Does a shallow clone of oldAggRel and updates aggCalls.
protected void	newCalcRel(RelBuilder relBuilder, RelDataType rowType, List<RexNode> exprs) Adds a calculation with the expressions to compute the original aggregate calls from the decomposed ones.
void	onMatch(RelOptRuleCall ruleCall) Receives notification about a rule match.

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

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

Methods inherited from class java.lang.Object

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

Constructor Detail

AggregateReduceFunctionsRule

protected AggregateReduceFunctionsRule(AggregateReduceFunctionsRule.Config config)

Creates an AggregateReduceFunctionsRule.

AggregateReduceFunctionsRule

@Deprecated
public AggregateReduceFunctionsRule(RelOptRuleOperand operand,
                                                RelBuilderFactory relBuilderFactory)

Deprecated.

AggregateReduceFunctionsRule

@Deprecated
public AggregateReduceFunctionsRule(Class<? extends Aggregate> aggregateClass,
                                                RelBuilderFactory relBuilderFactory,
                                                EnumSet<SqlKind> functionsToReduce)

Deprecated.

Method Detail

matches

public boolean matches(RelOptRuleCall call)

Description copied from class: RelOptRule

Returns whether this rule could possibly match the given operands.

This method is an opportunity to apply side-conditions to a rule. The RelOptPlanner calls this method after matching all operands of the rule, and before calling RelOptRule.onMatch(RelOptRuleCall).

In implementations of RelOptPlanner which may queue up a matched RelOptRuleCall for a long time before calling RelOptRule.onMatch(RelOptRuleCall), this method is beneficial because it allows the planner to discard rules earlier in the process.

The default implementation of this method returns true. It is acceptable for any implementation of this method to give a false positives, that is, to say that the rule matches the operands but have RelOptRule.onMatch(RelOptRuleCall) subsequently not generate any successors.

The following script is useful to identify rules which commonly produce no successors. You should override this method for these rules:

awk '
 /Apply rule/ {rule=$4; ruleCount[rule]++;}
 /generated 0 successors/ {ruleMiss[rule]++;}
 END {
   printf "%-30s %s %s\n", "Rule", "Fire", "Miss";
   for (i in ruleCount) {
     printf "%-30s %5d %5d\n", i, ruleCount[i], ruleMiss[i];
   }
 } ' FarragoTrace.log

Overrides:

matches in class RelOptRule

Parameters:

call - Rule call which has been determined to match all operands of this rule

Returns:

whether this RelOptRule matches a given RelOptRuleCall

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.apache.calcite.rel.RelNode, java.util.Map<org.apache.calcite.rel.RelNode, org.apache.calcite.rel.RelNode>, org.apache.calcite.plan.RelHintsPropagator) to register the expression.

Specified by:

onMatch in class RelOptRule

Parameters:

ruleCall - Rule call

See Also:

RelOptRule.matches(RelOptRuleCall)

canReduce

public boolean canReduce(AggregateCall call)

Returns whether this rule can reduce a given aggregate function call.

canReduceAggCallByGrouping

public boolean canReduceAggCallByGrouping(Aggregate oldAggRel,
                                          AggregateCall call)

Returns whether this rule can reduce some agg-call, which its arg exists in the aggregate's group.

newAggregateRel

protected void newAggregateRel(RelBuilder relBuilder,
                               Aggregate oldAggregate,
                               List<AggregateCall> newCalls)

Does a shallow clone of oldAggRel and updates 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(RelBuilder relBuilder,
                          RelDataType rowType,
                          List<RexNode> exprs)

Adds a calculation with the expressions to compute the original aggregate calls from the decomposed ones.

Parameters:

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

rowType - The output row type of the original aggregate.

exprs - The expressions to compute the original aggregate calls