Package org.apache.flink.table.planner.functions.aggfunctions

Class LeadLagAggFunction

java.lang.Object

org.apache.flink.table.functions.UserDefinedFunction

org.apache.flink.table.functions.DeclarativeAggregateFunction

org.apache.flink.table.planner.functions.aggfunctions.LeadLagAggFunction

All Implemented Interfaces:

Serializable, FunctionDefinition

Direct Known Subclasses:

LeadLagAggFunction.BooleanLeadLagAggFunction, LeadLagAggFunction.ByteLeadLagAggFunction, LeadLagAggFunction.CharLeadLagAggFunction, LeadLagAggFunction.DateLeadLagAggFunction, LeadLagAggFunction.DecimalLeadLagAggFunction, LeadLagAggFunction.DoubleLeadLagAggFunction, LeadLagAggFunction.FloatLeadLagAggFunction, LeadLagAggFunction.IntLeadLagAggFunction, LeadLagAggFunction.LongLeadLagAggFunction, LeadLagAggFunction.ShortLeadLagAggFunction, LeadLagAggFunction.StringLeadLagAggFunction, LeadLagAggFunction.TimeLeadLagAggFunction, LeadLagAggFunction.TimestampLeadLagAggFunction

public abstract class LeadLagAggFunction
extends DeclarativeAggregateFunction

LEAD and LAG aggregate functions return the value of given expression evaluated at given offset. The functions only are used by over window.

LAG(input, offset, default) - Returns the value of `input` at the `offset`th row before the current row in the window. The default value of `offset` is 1 and the default value of `default` is null. If the value of `input` at the `offset`th row is null, null is returned. If there is no such offset row (e.g., when the offset is 1, the first row of the window does not have any previous row), `default` is returned.

LEAD(input, offset, default) - Returns the value of `input` at the `offset`th row after the current row in the window. The default value of `offset` is 1 and the default value of `default` is null. If the value of `input` at the `offset`th row is null, null is returned. If there is no such an offset row (e.g., when the offset is 1, the last row of the window does not have any subsequent row), `default` is returned.

These two aggregate functions are special, and only are used by over window. So here the concrete implementation is closely related to OffsetOverFrame.

See Also:

Serialized Form

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static class	LeadLagAggFunction.BooleanLeadLagAggFunction	BooleanLeadLagAggFunction.
static class	LeadLagAggFunction.ByteLeadLagAggFunction	ByteLeadLagAggFunction.
static class	LeadLagAggFunction.CharLeadLagAggFunction	CharLeadLagAggFunction.
static class	LeadLagAggFunction.DateLeadLagAggFunction	DateLeadLagAggFunction.
static class	LeadLagAggFunction.DecimalLeadLagAggFunction	DecimalLeadLagAggFunction.
static class	LeadLagAggFunction.DoubleLeadLagAggFunction	DoubleLeadLagAggFunction.
static class	LeadLagAggFunction.FloatLeadLagAggFunction	FloatLeadLagAggFunction.
static class	LeadLagAggFunction.IntLeadLagAggFunction	IntLeadLagAggFunction.
static class	LeadLagAggFunction.LongLeadLagAggFunction	LongLeadLagAggFunction.
static class	LeadLagAggFunction.ShortLeadLagAggFunction	ShortLeadLagAggFunction.
static class	LeadLagAggFunction.StringLeadLagAggFunction	StringLeadLagAggFunction.
static class	LeadLagAggFunction.TimeLeadLagAggFunction	TimeLeadLagAggFunction.
static class	LeadLagAggFunction.TimestampLeadLagAggFunction	TimestampLeadLagAggFunction.

Constructor Summary

Constructors

Constructor	Description
LeadLagAggFunction(int operandCount)

Method Summary

Modifier and Type	Method	Description
Expression[]	accumulateExpressions()	Expressions for accumulating the mutable aggregation buffer based on an input row.
UnresolvedReferenceExpression[]	aggBufferAttributes()	All fields of the aggregate buffer.
DataType[]	getAggBufferTypes()	All types of the aggregate buffer.
Expression	getValueExpression()	An expression which returns the final value for this aggregate function.
Expression[]	initialValuesExpressions()	Expressions for initializing empty aggregation buffers.
Expression[]	mergeExpressions()	A sequence of expressions for merging two aggregation buffers together.
int	operandCount()	How many operands your function will deal with.
Expression[]	retractExpressions()	Expressions for retracting the mutable aggregation buffer based on an input row.

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

getKind, getResultType, getTypeInference, mergeOperand, mergeOperands, operand, operands

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

LeadLagAggFunction

public LeadLagAggFunction(int operandCount)

Method Detail

operandCount

public int operandCount()

Description copied from class: DeclarativeAggregateFunction

How many operands your function will deal with.

Specified by:

operandCount in class DeclarativeAggregateFunction

aggBufferAttributes

public UnresolvedReferenceExpression[] aggBufferAttributes()

Description copied from class: DeclarativeAggregateFunction

All fields of the aggregate buffer.

Specified by:

aggBufferAttributes in class DeclarativeAggregateFunction

getAggBufferTypes

public DataType[] getAggBufferTypes()

Description copied from class: DeclarativeAggregateFunction

All types of the aggregate buffer.

Specified by:

getAggBufferTypes in class DeclarativeAggregateFunction

initialValuesExpressions

public Expression[] initialValuesExpressions()

Description copied from class: DeclarativeAggregateFunction

Expressions for initializing empty aggregation buffers.

Specified by:

initialValuesExpressions in class DeclarativeAggregateFunction

accumulateExpressions

public Expression[] accumulateExpressions()

Description copied from class: DeclarativeAggregateFunction

Expressions for accumulating the mutable aggregation buffer based on an input row.

Specified by:

accumulateExpressions in class DeclarativeAggregateFunction

retractExpressions

public Expression[] retractExpressions()

Description copied from class: DeclarativeAggregateFunction

Expressions for retracting the mutable aggregation buffer based on an input row.

Specified by:

retractExpressions in class DeclarativeAggregateFunction

mergeExpressions

public Expression[] mergeExpressions()

Description copied from class: DeclarativeAggregateFunction

A sequence of expressions for merging two aggregation buffers together. When defining these expressions, you can use the syntax attributeName and mergeOperand(attributeName) to refer to the attributes corresponding to each of the buffers being merged.

Specified by:

mergeExpressions in class DeclarativeAggregateFunction

getValueExpression

public Expression getValueExpression()

Description copied from class: DeclarativeAggregateFunction

An expression which returns the final value for this aggregate function.

Specified by:

getValueExpression in class DeclarativeAggregateFunction