Package org.apache.flink.table.examples.java.functions

Class LastDatedValueFunction<T>

java.lang.Object

org.apache.flink.table.functions.UserDefinedFunction

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

org.apache.flink.table.functions.AggregateFunction<Row,LastDatedValueFunction.Accumulator<T>>

org.apache.flink.table.examples.java.functions.LastDatedValueFunction<T>

Type Parameters:

T - input value

All Implemented Interfaces:

Serializable, FunctionDefinition

public final class LastDatedValueFunction<T>
extends AggregateFunction<Row,LastDatedValueFunction.Accumulator<T>>

Implementation of an AggregateFunction that returns a row containing the latest non-null value with its corresponding date.

The function uses a custom TypeInference and thus disables any of the default reflection-based logic. It has a generic parameter T which will result in Object (due to type erasure) during runtime. The TypeInference will provide the necessary information how to call accumulate(...) for the given call in the query.

For code readability, we might use some internal utility methods that should rarely change. Implementers can copy those if they don't want to rely on non-official API.

See Also:

Serialized Form

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static class	LastDatedValueFunction.Accumulator<T>	Generic accumulator for representing state.

Constructor Summary

Constructors

Constructor	Description
LastDatedValueFunction()

Method Summary

Modifier and Type	Method	Description
void	accumulate(LastDatedValueFunction.Accumulator<T> acc, T input, LocalDate date)	Generic runtime function that will be called with different kind of instances for input depending on actual call in the query.
LastDatedValueFunction.Accumulator<T>	createAccumulator()	Creates and initializes the accumulator for this ImperativeAggregateFunction.
TypeInference	getTypeInference(DataTypeFactory typeFactory)	Declares the TypeInference of this function.
Row	getValue(LastDatedValueFunction.Accumulator<T> acc)	Called every time when an aggregation result should be materialized.

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

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

getRequirements, isDeterministic, supportsConstantFolding

Constructor Detail

LastDatedValueFunction

public LastDatedValueFunction()

Method Detail

getTypeInference

public TypeInference getTypeInference(DataTypeFactory typeFactory)

Declares the TypeInference of this function. It specifies:

• which argument types are supported when calling this function,
• which DataType.getConversionClass() should be used when calling the JVM method accumulate(Accumulator, Object, LocalDate) during runtime,
• a similar strategy how to derive an accumulator type,
• and a similar strategy how to derive the output type.

Specified by:

getTypeInference in interface FunctionDefinition

Overrides:

getTypeInference in class AggregateFunction<Row,LastDatedValueFunction.Accumulator<T>>

createAccumulator

public LastDatedValueFunction.Accumulator<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<Row,LastDatedValueFunction.Accumulator<T>>

Returns:

the accumulator with the initial value

accumulate

public void accumulate(LastDatedValueFunction.Accumulator<T> acc,
                       T input,
                       LocalDate date)

Generic runtime function that will be called with different kind of instances for input depending on actual call in the query.

getValue

public Row getValue(LastDatedValueFunction.Accumulator<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<Row,LastDatedValueFunction.Accumulator<T>>

Parameters:

acc - the accumulator which contains the current intermediate results

Returns:

the aggregation result