Package org.apache.qpid.server.query.engine.parsing.expression.function.aggregation

Class AvgExpression<T>

java.lang.Object

org.apache.qpid.server.query.engine.parsing.expression.AbstractExpressionNode<T,R>

org.apache.qpid.server.query.engine.parsing.expression.function.AbstractFunctionExpression<T,R>

org.apache.qpid.server.query.engine.parsing.expression.function.aggregation.AbstractAggregationExpression<T,Double>

org.apache.qpid.server.query.engine.parsing.expression.function.aggregation.AvgExpression<T>

Type Parameters:

T - Input parameter type

All Implemented Interfaces:

Function<T,Double>, Expression<T,Double>, ExpressionNode<T,Double>

public class AvgExpression<T>
extends AbstractAggregationExpression<T,Double>

The AVG() function returns the average value of a numeric collection.

Field Summary

Fields inherited from class org.apache.qpid.server.query.engine.parsing.expression.function.AbstractFunctionExpression

_functionName

Fields inherited from class org.apache.qpid.server.query.engine.parsing.expression.AbstractExpressionNode

_metadata

Constructor Summary

Constructors

Constructor	Description
AvgExpression(String alias, List<ExpressionNode<T,?>> args)	Constructor initializes children expression list

Method Summary

Modifier and Type	Method	Description
Double	aggregate(List<T> items)	Performs avg operation using parameters and the value supplied
CollectorType	getCollectorType()	Returns averaging collector type

Methods inherited from class org.apache.qpid.server.query.engine.parsing.expression.function.aggregation.AbstractAggregationExpression

apply, getArguments, getSource, setSelect, setValue

Methods inherited from class org.apache.qpid.server.query.engine.parsing.expression.function.AbstractFunctionExpression

evaluateChild, getFunctionName, getOptionalConstantParameter, getOptionalParameter, getRequiredParameter

Methods inherited from class org.apache.qpid.server.query.engine.parsing.expression.AbstractExpressionNode

containsAggregation, ctx, evaluateChild, getAggregations, getAlias, getChild, getChildren, getParent, isAccessor, isInstantlyEvaluable, setAlias, setParent, toString

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.apache.qpid.server.query.engine.parsing.expression.Expression

andThen

Methods inherited from interface java.util.function.Function

andThen, compose

Constructor Detail

AvgExpression

public AvgExpression(String alias,
                     List<ExpressionNode<T,?>> args)

Constructor initializes children expression list

Parameters:

alias - Expression alias

args - List of children expressions

Method Detail

getCollectorType

public CollectorType getCollectorType()

Returns averaging collector type

Specified by:

getCollectorType in class AbstractAggregationExpression<T,Double>

Returns:

CollectorType instance

aggregate

public Double aggregate(List<T> items)

Performs avg operation using parameters and the value supplied

Specified by:

aggregate in class AbstractAggregationExpression<T,Double>

Parameters:

items - Collection to perform aggregation on

Returns:

Aggregated result