Package dev.frostlake.functions.aggregate

Class CovarAccumulator

java.lang.Object

dev.frostlake.functions.aggregate.CovarAccumulator

All Implemented Interfaces:

AggregateFunction.Accumulator

public class CovarAccumulator
extends Object
implements AggregateFunction.Accumulator

Field Summary

Fields

Modifier and Type	Field	Description
long	n
double	sumX
double	sumXY
double	sumY

Constructor Summary

Constructors

Constructor	Description
CovarAccumulator(boolean sample)

Method Summary

Modifier and Type	Method	Description
void	accumulate(double x, double y)
void	accumulate(Object v)	Folds one row's argument value into the running state.
Object	getResult()	The aggregate's result over everything accumulated so far.
void	merge(AggregateFunction.Accumulator other)	Folds another accumulator's state into this one, combining two partial aggregations of the same group.
void	reset()	Clears the state back to the empty-group starting point so the accumulator can be reused.

Methods inherited from class java.lang.Object

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

Field Details

n

public long n

sumX

public double sumX

sumY

public double sumY

sumXY

public double sumXY

Constructor Details

CovarAccumulator

public CovarAccumulator(boolean sample)

Method Details

accumulate

public void accumulate(Object v)

Description copied from interface: AggregateFunction.Accumulator

Folds one row's argument value into the running state.

Specified by:

accumulate in interface AggregateFunction.Accumulator

Parameters:

v - the aggregate argument's value for one row; SQL NULL arrives as null

accumulate

public void accumulate(double x,
 double y)

getResult

public Object getResult()

Description copied from interface: AggregateFunction.Accumulator

The aggregate's result over everything accumulated so far.

Specified by:

getResult in interface AggregateFunction.Accumulator

Returns:

the group's result, or null where the aggregate defines an empty group as NULL

reset

public void reset()

Description copied from interface: AggregateFunction.Accumulator

Clears the state back to the empty-group starting point so the accumulator can be reused.

Specified by:

reset in interface AggregateFunction.Accumulator

merge

public void merge(AggregateFunction.Accumulator other)

Description copied from interface: AggregateFunction.Accumulator

Folds another accumulator's state into this one, combining two partial aggregations of the same group.

Specified by:

merge in interface AggregateFunction.Accumulator

Parameters:

other - a partial state of the same aggregate implementation