org.apache.druid.query.aggregation

Class NullableAggregator

java.lang.Object

org.apache.druid.query.aggregation.NullableAggregator

All Implemented Interfaces:

Closeable, AutoCloseable, Aggregator

public final class NullableAggregator
extends Object
implements Aggregator

The result of a NullableAggregator will be null if all the values to be aggregated are null values or no values are aggregated at all. If any of the value is non-null, the result would be the aggregated value of the delegate aggregator. Note that the delegate aggregator is not required to perform check for BaseNullableColumnValueSelector.isNull() on the selector as only non-null values will be passed to the delegate aggregator. This class is only used when SQL compatible null handling is enabled.

Constructor Summary

Constructors

Constructor and Description
NullableAggregator(Aggregator delegate, BaseNullableColumnValueSelector selector)

Method Summary

Modifier and Type	Method and Description
void	aggregate()
void	close()
Object	get()
double	getDouble() The default implementation casts Aggregator.getFloat() to double.
float	getFloat()
long	getLong()
boolean	isNull() returns true if aggregator's output type is primitive long/double/float and aggregated value is null, but when aggregated output type is Object, this method always returns false, and users are advised to check nullability for the object returned by Aggregator.get() method.

Methods inherited from class java.lang.Object

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

Constructor Detail

NullableAggregator

public NullableAggregator(Aggregator delegate,
                          BaseNullableColumnValueSelector selector)

Method Detail

aggregate

public void aggregate()

Specified by:

aggregate in interface Aggregator

get

@Nullable
public Object get()

Specified by:

get in interface Aggregator

getFloat

public float getFloat()

Specified by:

getFloat in interface Aggregator

getLong

public long getLong()

Specified by:

getLong in interface Aggregator

getDouble

public double getDouble()

Description copied from interface: Aggregator

The default implementation casts Aggregator.getFloat() to double. This default method is added to enable smooth backward compatibility, please re-implement it if your aggregators work with numeric double columns.

Specified by:

getDouble in interface Aggregator

isNull

public boolean isNull()

Description copied from interface: Aggregator

returns true if aggregator's output type is primitive long/double/float and aggregated value is null, but when aggregated output type is Object, this method always returns false, and users are advised to check nullability for the object returned by Aggregator.get() method. The default implementation always return false to enable smooth backward compatibility, re-implement if your aggregator is nullable.

Specified by:

isNull in interface Aggregator

close

public void close()

Specified by:

close in interface Closeable

Specified by:

close in interface AutoCloseable

Specified by:

close in interface Aggregator