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 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(RelOptRuleOperand operand, RelBuilderFactory relBuilderFactory) Creates an AggregateReduceFunctionsRule.

Method Summary

Modifier and Type	Method and Description
private boolean	containsAvgStddevVarCall(List<AggregateCall> aggCallList) Returns whether any of the aggregates are calls to AVG, STDDEV_*, VAR_*.
private AggregateCall	createAggregateCallWithBinding(RelDataTypeFactory typeFactory, SqlAggFunction aggFunction, RelDataType operandType, Aggregate oldAggRel, AggregateCall oldCall, int argOrdinal)
private RelDataType	getFieldType(RelNode relNode, int i)
private boolean	isReducible(SqlKind kind) Returns whether the aggregate call is a reducible function
private static <T> int	lookupOrAdd(List<T> list, T element) Finds the ordinal of an element in a list, or adds it.
boolean	matches(RelOptRuleCall call) Returns whether this rule could possibly match the given operands.
protected void	newAggregateRel(RelBuilder relBuilder, Aggregate oldAggregate, List<AggregateCall> newCalls) Do a shallow clone of oldAggRel and update aggCalls.
void	onMatch(RelOptRuleCall ruleCall) Receives notification about a rule match.
private RexNode	reduceAgg(Aggregate oldAggRel, AggregateCall oldCall, List<AggregateCall> newCalls, Map<AggregateCall,RexNode> aggCallMapping, List<RexNode> inputExprs)
private void	reduceAggs(RelOptRuleCall ruleCall, Aggregate oldAggRel) Reduces all calls to AVG, STDDEV_POP, STDDEV_SAMP, VAR_POP, VAR_SAMP in the aggregates list to.
private RexNode	reduceAvg(Aggregate oldAggRel, AggregateCall oldCall, List<AggregateCall> newCalls, Map<AggregateCall,RexNode> aggCallMapping, List<RexNode> inputExprs)
private RexNode	reduceStddev(Aggregate oldAggRel, AggregateCall oldCall, boolean biased, boolean sqrt, List<AggregateCall> newCalls, Map<AggregateCall,RexNode> aggCallMapping, List<RexNode> inputExprs)
private RexNode	reduceSum(Aggregate oldAggRel, AggregateCall oldCall, List<AggregateCall> newCalls, Map<AggregateCall,RexNode> aggCallMapping)

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(RelOptRuleOperand operand,
                                    RelBuilderFactory relBuilderFactory)

Creates an AggregateReduceFunctionsRule.

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>) to register the expression.

Specified by:

onMatch in class RelOptRule

Parameters:

ruleCall - Rule call

See Also:

RelOptRule.matches(RelOptRuleCall)

containsAvgStddevVarCall

private boolean containsAvgStddevVarCall(List<AggregateCall> aggCallList)

Returns whether any of the aggregates are calls to AVG, STDDEV_*, VAR_*.

Parameters:

aggCallList - List of aggregate calls

isReducible

private boolean isReducible(SqlKind kind)

Returns whether the aggregate call is a reducible function

reduceAggs

private void reduceAggs(RelOptRuleCall ruleCall,
                        Aggregate oldAggRel)

Reduces all calls to AVG, STDDEV_POP, STDDEV_SAMP, VAR_POP, VAR_SAMP in the aggregates list to.

It handles newly generated common subexpressions since this was done at the sql2rel stage.

reduceAgg

private RexNode reduceAgg(Aggregate oldAggRel,
                          AggregateCall oldCall,
                          List<AggregateCall> newCalls,
                          Map<AggregateCall,RexNode> aggCallMapping,
                          List<RexNode> inputExprs)

createAggregateCallWithBinding

private AggregateCall createAggregateCallWithBinding(RelDataTypeFactory typeFactory,
                                                     SqlAggFunction aggFunction,
                                                     RelDataType operandType,
                                                     Aggregate oldAggRel,
                                                     AggregateCall oldCall,
                                                     int argOrdinal)

reduceAvg

private RexNode reduceAvg(Aggregate oldAggRel,
                          AggregateCall oldCall,
                          List<AggregateCall> newCalls,
                          Map<AggregateCall,RexNode> aggCallMapping,
                          List<RexNode> inputExprs)

reduceSum

private RexNode reduceSum(Aggregate oldAggRel,
                          AggregateCall oldCall,
                          List<AggregateCall> newCalls,
                          Map<AggregateCall,RexNode> aggCallMapping)

reduceStddev

private RexNode reduceStddev(Aggregate oldAggRel,
                             AggregateCall oldCall,
                             boolean biased,
                             boolean sqrt,
                             List<AggregateCall> newCalls,
                             Map<AggregateCall,RexNode> aggCallMapping,
                             List<RexNode> inputExprs)

lookupOrAdd

private static <T> int lookupOrAdd(List<T> list,
                                   T element)

Finds the ordinal of an element in a list, or adds it.

Type Parameters:

T - Element type

Parameters:

list - List

element - Element to lookup or add

Returns:

Ordinal of element in list

newAggregateRel

protected void newAggregateRel(RelBuilder relBuilder,
                               Aggregate oldAggregate,
                               List<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

getFieldType

private RelDataType getFieldType(RelNode relNode,
                                 int i)