org.apache.flink.table.functions

Class UserDefinedAggregateFunction<T,ACC>

java.lang.Object

org.apache.flink.table.functions.UserDefinedFunction

org.apache.flink.table.functions.UserDefinedAggregateFunction<T,ACC>

All Implemented Interfaces:

Serializable, FunctionDefinition

Direct Known Subclasses:

AggregateFunction, TableAggregateFunction

@PublicEvolving
public abstract class UserDefinedAggregateFunction<T,ACC>
extends UserDefinedFunction

Base class for user-defined aggregates and table aggregates.

See Also:

Serialized Form

Constructor Summary

Constructors

Constructor and Description
UserDefinedAggregateFunction()

Method Summary

Modifier and Type	Method and Description
abstract ACC	createAccumulator() Creates and initializes the accumulator for this UserDefinedAggregateFunction.
org.apache.flink.api.common.typeinfo.TypeInformation<ACC>	getAccumulatorType() Returns the TypeInformation of the UserDefinedAggregateFunction's accumulator.
org.apache.flink.api.common.typeinfo.TypeInformation<T>	getResultType() Returns the TypeInformation of the UserDefinedAggregateFunction's result.

Methods inherited from class org.apache.flink.table.functions.UserDefinedFunction

close, functionIdentifier, open, toString

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.apache.flink.table.functions.FunctionDefinition

getKind, getRequirements, isDeterministic

Constructor Detail

UserDefinedAggregateFunction

public UserDefinedAggregateFunction()

Method Detail

createAccumulator

public abstract ACC createAccumulator()

Creates and initializes the accumulator for this UserDefinedAggregateFunction. The accumulator is used to keep the aggregated values which are needed to compute an aggregation result.

Returns:

the accumulator with the initial value

getResultType

public org.apache.flink.api.common.typeinfo.TypeInformation<T> getResultType()

Returns the TypeInformation of the UserDefinedAggregateFunction's result.

Returns:

The TypeInformation of the UserDefinedAggregateFunction's result or null if the result type should be automatically inferred.

getAccumulatorType

public org.apache.flink.api.common.typeinfo.TypeInformation<ACC> getAccumulatorType()

Returns the TypeInformation of the UserDefinedAggregateFunction's accumulator.

Returns:

The TypeInformation of the UserDefinedAggregateFunction's accumulator or null if the accumulator type should be automatically inferred.