Package org.apache.druid.segment

Interface BaseObjectColumnValueSelector<T>

All Known Subinterfaces:

AggregateCombiner<T>, ColumnValueSelector<T>, DimensionSelector, DoubleColumnSelector, FloatColumnSelector, HistoricalColumnSelector<T>, HistoricalDimensionSelector, LongColumnSelector, SettableColumnValueSelector<T>, SingleValueHistoricalDimensionSelector

All Known Implementing Classes:

AbstractDimensionSelector, BaseExpressionColumnValueSelector, BaseSingleValueDimensionSelector, ConstantDimensionSelector, ConstantExprEvalSelector, ConstantMultiValueDimensionSelector, DoubleAggregateCombiner, DoubleWrappingDimensionSelector, ExpressionColumnValueSelector, ExpressionMultiValueDimensionSelector, FloatWrappingDimensionSelector, GenericFirstAggregateCombiner, GenericLastAggregateCombiner, HyperLogLogCollectorAggregateCombiner, IncrementalIndexRowHolder, IndexedTableColumnValueSelector, IndexedTableDimensionSelector, LongAggregateCombiner, LongSumAggregateCombiner, LongWrappingDimensionSelector, NestedFieldVirtualColumn.FieldDimensionSelector, NestedFieldVirtualColumn.RawFieldColumnSelector, NestedFieldVirtualColumn.RawFieldLiteralColumnValueSelector, NilColumnValueSelector, NullableNumericAggregateCombiner, NumericArrayFieldSelector, ObjectAggregateCombiner, ObjectBasedColumnSelector, ObjectColumnSelector, ObjectToArrayColumnValueSelector, ObjectToNumberColumnValueSelector, PossiblyNullColumnValueSelector, PossiblyNullDimensionSelector, RowBasedExpressionColumnValueSelector, SettableDimensionValueSelector, SettableDoubleColumnValueSelector, SettableFloatColumnValueSelector, SettableLongColumnValueSelector, SettableObjectColumnValueSelector, SingleLongInputCachingExpressionColumnValueSelector, SingleScanTimeDimensionSelector, SingleStringInputCachingExpressionColumnValueSelector, SingleStringInputDeferredEvaluationExpressionDimensionSelector

public interface BaseObjectColumnValueSelector<T>

Object value selecting polymorphic "part" of the ColumnValueSelector interface. Users of getObject() are encouraged to reduce the parameter/field/etc. type to BaseObjectColumnValueSelector to make it impossible to accidently call any method other than getObject(). All implementations of this interface MUST also implement ColumnValueSelector. Typically created by ColumnSelectorFactory.makeColumnValueSelector(String).

Method Summary

Modifier and Type	Method	Description
Class<? extends T>	classOfObject()	Most-specific class of object returned by getObject(), if known in advance.
T	getObject()	Returns the currently-selected object.

Method Detail

getObject

@Nullable
T getObject()

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

Class<? extends T> classOfObject()

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