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

Class AbstractAggregationExpression<T,R>

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,R>

Type Parameters:

T - Input parameter type

R - Output parameter type

All Implemented Interfaces:

Function<T,R>, Expression<T,R>, ExpressionNode<T,R>

Direct Known Subclasses:

AvgExpression, CountExpression, MaxExpression, MinExpression, SumExpression

public abstract class AbstractAggregationExpression<T,R>
extends AbstractFunctionExpression<T,R>

Parent for aggregation function classes

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

Method Summary

Modifier and Type	Method	Description
abstract R	aggregate(List<T> items)	Aggregation implementation
R	apply(T value)	Should be called after aggregate() method returning cached result.
protected List<?>	getArguments(List<T> items, FunctionParameterTypePredicate<Object> _typeValidator)	Evaluates and validates input collection values
abstract CollectorType	getCollectorType()	Type of the collector depends on the aggregation type
Expression<T,R>	getSource()
void	setSelect(SelectExpression<T,R> selectExpression)
void	setValue(R value)

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

AbstractAggregationExpression

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

Constructor initializes children expression list

Parameters:

alias - Expression alias

args - List of children expressions

Method Detail

apply

public R apply(T value)

Should be called after aggregate() method returning cached result. When query contains HAVING clause, extracts result from the nested map.

Parameters:

value - Object to handle

Returns:

Aggregation result

getArguments

protected List<?> getArguments(List<T> items,
                               FunctionParameterTypePredicate<Object> _typeValidator)

Evaluates and validates input collection values

Parameters:

items - Input collection

_typeValidator - Argument type validator

Returns:

List of evaluated values

aggregate

public abstract R aggregate(List<T> items)

Aggregation implementation

Parameters:

items - Collection to perform aggregation on

Returns:

Aggregation result

getCollectorType

public abstract CollectorType getCollectorType()

Type of the collector depends on the aggregation type

Returns:

CollectorType instance

setValue

public void setValue(R value)

setSelect

public void setSelect(SelectExpression<T,R> selectExpression)

getSource

public Expression<T,R> getSource()