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, org.apache.flink.table.functions.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 org.apache.flink.table.functions.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 and 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 and Description
LeadLagAggFunction(int operandCount)

Method Summary

Modifier and Type	Method and Description
org.apache.flink.table.expressions.Expression[]	accumulateExpressions()
org.apache.flink.table.expressions.UnresolvedReferenceExpression[]	aggBufferAttributes()
org.apache.flink.table.types.DataType[]	getAggBufferTypes()
org.apache.flink.table.expressions.Expression	getValueExpression()
org.apache.flink.table.expressions.Expression[]	initialValuesExpressions()
org.apache.flink.table.expressions.Expression[]	mergeExpressions()
int	operandCount()
org.apache.flink.table.expressions.Expression[]	retractExpressions()

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

Constructor Detail

LeadLagAggFunction

public LeadLagAggFunction(int operandCount)

Method Detail

operandCount

public int operandCount()

Specified by:

operandCount in class org.apache.flink.table.functions.DeclarativeAggregateFunction

aggBufferAttributes

public org.apache.flink.table.expressions.UnresolvedReferenceExpression[] aggBufferAttributes()

Specified by:

aggBufferAttributes in class org.apache.flink.table.functions.DeclarativeAggregateFunction

getAggBufferTypes

public org.apache.flink.table.types.DataType[] getAggBufferTypes()

Specified by:

getAggBufferTypes in class org.apache.flink.table.functions.DeclarativeAggregateFunction

initialValuesExpressions

public org.apache.flink.table.expressions.Expression[] initialValuesExpressions()

Specified by:

initialValuesExpressions in class org.apache.flink.table.functions.DeclarativeAggregateFunction

accumulateExpressions

public org.apache.flink.table.expressions.Expression[] accumulateExpressions()

Specified by:

accumulateExpressions in class org.apache.flink.table.functions.DeclarativeAggregateFunction

retractExpressions

public org.apache.flink.table.expressions.Expression[] retractExpressions()

Specified by:

retractExpressions in class org.apache.flink.table.functions.DeclarativeAggregateFunction

mergeExpressions

public org.apache.flink.table.expressions.Expression[] mergeExpressions()

Specified by:

mergeExpressions in class org.apache.flink.table.functions.DeclarativeAggregateFunction

getValueExpression

public org.apache.flink.table.expressions.Expression getValueExpression()

Specified by:

getValueExpression in class org.apache.flink.table.functions.DeclarativeAggregateFunction