org.apache.flink.table.runtime.functions.aggregate

Class FirstValueAggFunction<T>

java.lang.Object

org.apache.flink.table.functions.UserDefinedFunction

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

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

org.apache.flink.table.runtime.functions.aggregate.BuiltInAggregateFunction<T,RowData>

org.apache.flink.table.runtime.functions.aggregate.FirstValueAggFunction<T>

All Implemented Interfaces:

Serializable, FunctionDefinition

@Internal
public final class FirstValueAggFunction<T>
extends BuiltInAggregateFunction<T,RowData>

Built-in FIRST_VALUE aggregate function.

See Also:

Serialized Form

Constructor Summary

Constructors

Constructor and Description
FirstValueAggFunction(LogicalType valueType)

Method Summary

Modifier and Type	Method and Description
void	accumulate(RowData rowData, Object value)
void	accumulate(RowData rowData, Object value, Long order)
void	accumulate(RowData rowData, StringData value)
void	accumulate(RowData rowData, StringData value, Long order)
RowData	createAccumulator() Creates and initializes the accumulator for this ImperativeAggregateFunction.
DataType	getAccumulatorDataType()
List<DataType>	getArgumentDataTypes()
DataType	getOutputDataType()
T	getValue(RowData acc) Called every time when an aggregation result should be materialized.
boolean	isDeterministic() Returns information about the determinism of the function's results.
void	resetAccumulator(RowData rowData)

Methods inherited from class org.apache.flink.table.runtime.functions.aggregate.BuiltInAggregateFunction

getRequirements, getTypeInference

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

getKind

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

getAccumulatorType, getResultType

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

Constructor Detail

FirstValueAggFunction

public FirstValueAggFunction(LogicalType valueType)

Method Detail

getArgumentDataTypes

public List<DataType> getArgumentDataTypes()

Overrides:

getArgumentDataTypes in class BuiltInAggregateFunction<T,RowData>

getAccumulatorDataType

public DataType getAccumulatorDataType()

Overrides:

getAccumulatorDataType in class BuiltInAggregateFunction<T,RowData>

getOutputDataType

public DataType getOutputDataType()

Overrides:

getOutputDataType in class BuiltInAggregateFunction<T,RowData>

isDeterministic

public boolean isDeterministic()

Description copied from interface: FunctionDefinition

Returns information about the determinism of the function's results.

It returns true if and only if a call to this function is guaranteed to always return the same result given the same parameters. true is assumed by default. If the function is not purely functional like random(), date(), now(), ... this method must return false.

Furthermore, return false if the planner should always execute this function on the cluster side. In other words: the planner should not perform constant expression reduction during planning for constant calls to this function.

Specified by:

isDeterministic in interface FunctionDefinition

Overrides:

isDeterministic in class BuiltInAggregateFunction<T,RowData>

createAccumulator

public RowData createAccumulator()

Description copied from class: ImperativeAggregateFunction

Creates and initializes the accumulator for this ImperativeAggregateFunction.

The accumulator is an intermediate data structure that stores the aggregated values until a final aggregation result is computed.

Specified by:

createAccumulator in class ImperativeAggregateFunction<T,RowData>

Returns:

the accumulator with the initial value

accumulate

public void accumulate(RowData rowData,
                       Object value)

accumulate

public void accumulate(RowData rowData,
                       Object value,
                       Long order)

accumulate

public void accumulate(RowData rowData,
                       StringData value)

accumulate

public void accumulate(RowData rowData,
                       StringData value,
                       Long order)

resetAccumulator

public void resetAccumulator(RowData rowData)

getValue

public T getValue(RowData acc)

Description copied from class: AggregateFunction

Called every time when an aggregation result should be materialized. The returned value could be either an early and incomplete result (periodically emitted as data arrives) or the final result of the aggregation.

Specified by:

getValue in class AggregateFunction<T,RowData>

Parameters:

acc - the accumulator which contains the current intermediate results

Returns:

the aggregation result