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

Class LagAggFunction<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,LagAggFunction.LagAcc<T>>

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

All Implemented Interfaces:

Serializable, FunctionDefinition

public class LagAggFunction<T>
extends BuiltInAggregateFunction<T,LagAggFunction.LagAcc<T>>

Lag AggregateFunction.

See Also:

Serialized Form

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	LagAggFunction.LagAcc<T> Accumulator for LAG.

Constructor Summary

Constructors

Constructor and Description
LagAggFunction(LogicalType[] valueTypes)

Method Summary

Modifier and Type	Method and Description
void	accumulate(LagAggFunction.LagAcc<T> acc, T value)
void	accumulate(LagAggFunction.LagAcc<T> acc, T value, int offset)
void	accumulate(LagAggFunction.LagAcc<T> acc, T value, int offset, T defaultValue)
LagAggFunction.LagAcc<T>	createAccumulator() Creates and initializes the accumulator for this ImperativeAggregateFunction.
DataType	getAccumulatorDataType()
List<DataType>	getArgumentDataTypes()
DataType	getOutputDataType()
T	getValue(LagAggFunction.LagAcc<T> acc) Called every time when an aggregation result should be materialized.
void	resetAccumulator(LagAggFunction.LagAcc<T> acc)

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

getRequirements, getTypeInference, isDeterministic

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

LagAggFunction

public LagAggFunction(LogicalType[] valueTypes)

Method Detail

getArgumentDataTypes

public List<DataType> getArgumentDataTypes()

Overrides:

getArgumentDataTypes in class BuiltInAggregateFunction<T,LagAggFunction.LagAcc<T>>

getAccumulatorDataType

public DataType getAccumulatorDataType()

Overrides:

getAccumulatorDataType in class BuiltInAggregateFunction<T,LagAggFunction.LagAcc<T>>

getOutputDataType

public DataType getOutputDataType()

Overrides:

getOutputDataType in class BuiltInAggregateFunction<T,LagAggFunction.LagAcc<T>>

accumulate

public void accumulate(LagAggFunction.LagAcc<T> acc,
                       T value)
                throws Exception

Throws:

Exception

accumulate

public void accumulate(LagAggFunction.LagAcc<T> acc,
                       T value,
                       int offset)
                throws Exception

Throws:

Exception

accumulate

public void accumulate(LagAggFunction.LagAcc<T> acc,
                       T value,
                       int offset,
                       T defaultValue)
                throws Exception

Throws:

Exception

resetAccumulator

public void resetAccumulator(LagAggFunction.LagAcc<T> acc)
                      throws Exception

Throws:

Exception

getValue

public T getValue(LagAggFunction.LagAcc<T> 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,LagAggFunction.LagAcc<T>>

Parameters:

acc - the accumulator which contains the current intermediate results

Returns:

the aggregation result

createAccumulator

public LagAggFunction.LagAcc<T> 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,LagAggFunction.LagAcc<T>>

Returns:

the accumulator with the initial value