org.apache.calcite.adapter.enumerable

Class RexImpTable.LagImplementor

java.lang.Object

org.apache.calcite.adapter.enumerable.RexImpTable.LagImplementor

All Implemented Interfaces:

AggImplementor, WinAggImplementor

Enclosing class:

RexImpTable

public static class RexImpTable.LagImplementor
extends Object

Implementor for the LAG windowed aggregate function.

Nested Class Summary

Nested classes/interfaces inherited from interface org.apache.calcite.adapter.enumerable.WinAggImplementor

WinAggImplementor.SeekType

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	RexImpTable.LagImplementor()

Method Summary

Methods

Modifier and Type	Method and Description
List<Type>	getStateType(AggContext info) Returns the types of the intermediate variables used by the aggregate implementation.
void	implementAdd(AggContext info, AggAddContext add) Updates intermediate values to account for the newly added value.
void	implementReset(AggContext info, AggResetContext reset) Implements reset of the intermediate variables to the initial state.
Expression	implementResult(AggContext info, AggResultContext result) Calculates the resulting value based on the intermediate variables.
boolean	needCacheWhenFrameIntact()

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

RexImpTable.LagImplementor

protected RexImpTable.LagImplementor()

Method Detail

getStateType

public List<Type> getStateType(AggContext info)

Description copied from interface: AggImplementor

Returns the types of the intermediate variables used by the aggregate implementation.

For instance, for "concatenate to string" this can be StringBuilder. Calcite calls this method before all other implement* methods.

Specified by:

getStateType in interface AggImplementor

Parameters:

info - Aggregate context

Returns:

Types of the intermediate variables used by the aggregate implementation

implementReset

public void implementReset(AggContext info,
                  AggResetContext reset)

Description copied from interface: AggImplementor

Implements reset of the intermediate variables to the initial state. AggResetContext.accumulator() should be used to reference the state variables. For instance, to zero the count, use the following code:

reset.currentBlock().add(
Expressions.statement(
Expressions.assign(reset.accumulator().get(0),
Expressions.constant(0)));

Specified by:

implementReset in interface AggImplementor

Parameters:

info - Aggregate context

reset - Reset context

implementAdd

public void implementAdd(AggContext info,
                AggAddContext add)

Description copied from interface: AggImplementor

Updates intermediate values to account for the newly added value. AggResetContext.accumulator() should be used to reference the state variables.

Specified by:

implementAdd in interface AggImplementor

Parameters:

info - Aggregate context

add - Add context

needCacheWhenFrameIntact

public boolean needCacheWhenFrameIntact()

Specified by:

needCacheWhenFrameIntact in interface WinAggImplementor

implementResult

public Expression implementResult(AggContext info,
                         AggResultContext result)

Description copied from interface: AggImplementor

Calculates the resulting value based on the intermediate variables. Note: this method must NOT destroy the intermediate variables as calcite might reuse the state when calculating sliding aggregates. AggResetContext.accumulator() should be used to reference the state variables.

Specified by:

implementResult in interface AggImplementor

Parameters:

info - Aggregate context

result - Result context

Returns:

Expression that is a result of calculating final value of the aggregate being implemented