Package org.apache.druid.query.aggregation.firstlast.first

Class GenericFirstAggregateCombiner<T extends SerializablePair<Long,?>>

java.lang.Object

org.apache.druid.segment.ObjectColumnSelector<T>

org.apache.druid.query.aggregation.ObjectAggregateCombiner<T>

org.apache.druid.query.aggregation.firstlast.first.GenericFirstAggregateCombiner<T>

All Implemented Interfaces:

AggregateCombiner<T>, HotLoopCallee, BaseDoubleColumnValueSelector, BaseFloatColumnValueSelector, BaseLongColumnValueSelector, BaseNullableColumnValueSelector, BaseObjectColumnValueSelector<T>, ColumnValueSelector<T>

public class GenericFirstAggregateCombiner<T extends SerializablePair<Long,?>>
extends ObjectAggregateCombiner<T>

Field Summary

Fields inherited from interface org.apache.druid.segment.ColumnValueSelector

EMPTY_ARRAY

Constructor Summary

Constructors

Constructor	Description
GenericFirstAggregateCombiner(Class<T> pairClass)

Method Summary

Modifier and Type	Method	Description
Class<T>	classOfObject()	Most-specific class of object returned by BaseObjectColumnValueSelector.getObject(), if known in advance.
void	fold(ColumnValueSelector selector)	Folds this AggregateCombiner's state value with the value of the given selector and saves it in this AggregateCombiner's state, e.
T	getObject()	Returns the currently-selected object.
void	reset(ColumnValueSelector selector)	Resets this AggregateCombiner's state value to the value of the given selector, e.

Methods inherited from class org.apache.druid.segment.ObjectColumnSelector

getDouble, getFloat, getLong, isNull

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.apache.druid.query.aggregation.AggregateCombiner

inspectRuntimeShape, isNull

Methods inherited from interface org.apache.druid.segment.BaseDoubleColumnValueSelector

getDouble

Methods inherited from interface org.apache.druid.segment.BaseFloatColumnValueSelector

getFloat

Methods inherited from interface org.apache.druid.segment.BaseLongColumnValueSelector

getLong

Constructor Details

GenericFirstAggregateCombiner

public GenericFirstAggregateCombiner(Class<T> pairClass)

Method Details

reset

public void reset(ColumnValueSelector selector)

Description copied from interface: AggregateCombiner

Resets this AggregateCombiner's state value to the value of the given selector, e. g. after calling this method combiner.get*() should return the same value as selector.get*(). If the selector is an ObjectColumnSelector, the object returned from BaseObjectColumnValueSelector.getObject() must not be modified, and must not become a subject for modification during subsequent AggregateCombiner.fold(org.apache.druid.segment.ColumnValueSelector) calls.

fold

public void fold(ColumnValueSelector selector)

Description copied from interface: AggregateCombiner

Folds this AggregateCombiner's state value with the value of the given selector and saves it in this AggregateCombiner's state, e. g. after calling combiner.fold(selector), combiner.get*() should return the value that would be the result of aggregatorFactory.combine(combiner.get*(), selector.get*()) call. Unlike AggregatorFactory.combine(java.lang.Object, java.lang.Object), if the selector is an ObjectColumnSelector, the object returned from BaseObjectColumnValueSelector.getObject() must not be modified, and must not become a subject for modification during subsequent fold() calls. Since the state of AggregateCombiner is undefined before AggregateCombiner.reset(org.apache.druid.segment.ColumnValueSelector) is ever called on it, the effects of calling fold() are also undefined in this case.

See Also:

• AggregatorFactory.combine(java.lang.Object, java.lang.Object)

getObject

@Nullable
public T getObject()

Description copied from interface: BaseObjectColumnValueSelector

Returns the currently-selected object. The behavior of this method depends on the type of selector, which can be determined by calling ColumnSelectorFactory.getColumnCapabilities(String) on the same ColumnSelectorFactory that you got this selector from. If the capabilties are nonnull, the selector type is given by TypeSignature.getType(). String selectors, where type is ColumnType.STRING, may return any type of object from this method, especially in cases where the selector is casting objects to string at selection time. Callers are encouraged to avoid the need to deal with various objects by using ColumnSelectorFactory.makeDimensionSelector(org.apache.druid.query.dimension.DimensionSpec) instead. Numeric selectors, where TypeSignature.isNumeric(), may return any type of Number. Callers that wish to deal with more specific types should treat the original ColumnValueSelector as a BaseLongColumnValueSelector, BaseDoubleColumnValueSelector, or BaseFloatColumnValueSelector instead. Array selectors, where TypeSignature.isArray(), must return Object[]. The array may contain null elements, and the array itself may also be null. Selectors of unknown type, where ColumnSelectorFactory.getColumnCapabilities(String) returns null, may return any type of object. Callers must be prepared for a wide variety of possible input objects. This case is common during ingestion, where selectors are built on top of external data.

classOfObject

public Class<T> classOfObject()

Description copied from interface: BaseObjectColumnValueSelector

Most-specific class of object returned by BaseObjectColumnValueSelector.getObject(), if known in advance. This method returns Object when selectors do not know in advance what class of object they may return.