org.apache.druid.segment

Interface DimensionSelector

All Superinterfaces:

BaseDoubleColumnValueSelector, BaseFloatColumnValueSelector, BaseLongColumnValueSelector, BaseNullableColumnValueSelector, BaseObjectColumnValueSelector<Object>, ColumnValueSelector<Object>, DimensionDictionarySelector, HotLoopCallee

All Known Subinterfaces:

HistoricalDimensionSelector, SingleValueHistoricalDimensionSelector

All Known Implementing Classes:

AbstractDimensionSelector, BaseSingleValueDimensionSelector, ConstantDimensionSelector, ConstantMultiValueDimensionSelector, DoubleWrappingDimensionSelector, ExpressionMultiValueDimensionSelector, FloatWrappingDimensionSelector, IndexedTableDimensionSelector, LongWrappingDimensionSelector, NestedFieldVirtualColumn.FieldDimensionSelector, PossiblyNullDimensionSelector, SettableDimensionValueSelector, SingleScanTimeDimensionSelector, SingleStringInputDeferredEvaluationExpressionDimensionSelector

public interface DimensionSelector
extends ColumnValueSelector<Object>, DimensionDictionarySelector, HotLoopCallee

Selector for a string-typed column, either single- or multi-valued. This is named a "dimension" selector for legacy reasons: in the past, all Druid dimensions were string-typed.

See Also:

org.apache.druid.segment.vector.SingleValueDimensionVectorSelector, a vectorized version, org.apache.druid.segment.vector.MultiValueDimensionVectorSelector, another vectorized version

Nested Class Summary

Nested Classes

Modifier and Type	Interface and Description
static class	DimensionSelector.NullDimensionSelectorHolder This class not a public API.

Field Summary

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

EMPTY_ARRAY

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

CARDINALITY_UNKNOWN

Method Summary

Modifier and Type	Method and Description
static DimensionSelector	constant(String value)
static DimensionSelector	constant(String value, ExtractionFn extractionFn)
default Object	defaultGetObject() Converts the current result of getRow() into null, if the row is empty, a String, if the row has size 1, or a String[] array, if the row has size > 1, using DimensionDictionarySelector.lookupName(int).
default double	getDouble() Deprecated. This method is marked as deprecated in DimensionSelector to minimize the probability of accidental calling. "Polymorphism" of DimensionSelector should be used only when operating on ColumnValueSelector objects.
default float	getFloat() Deprecated. This method is marked as deprecated in DimensionSelector to minimize the probability of accidental calling. "Polymorphism" of DimensionSelector should be used only when operating on ColumnValueSelector objects.
default long	getLong() Deprecated. This method is marked as deprecated in DimensionSelector to minimize the probability of accidental calling. "Polymorphism" of DimensionSelector should be used only when operating on ColumnValueSelector objects.
IndexedInts	getRow() Returns the indexed values at the current position in this DimensionSelector.
static boolean	isNilSelector(DimensionSelector selector) Checks if the given selector constantly returns null.
default boolean	isNull() Deprecated.
ValueMatcher	makeValueMatcher(com.google.common.base.Predicate<String> predicate)
ValueMatcher	makeValueMatcher(String value)
static DimensionSelector	multiConstant(List<String> values)
static DimensionSelector	multiConstant(List<String> values, ExtractionFn extractionFn)
static DimensionSelector	nilSelector()
static Object	rowToObject(IndexedInts row, DimensionDictionarySelector selector) Converts a particular IndexedInts to an Object in a standard way, assuming each element in the IndexedInts is a dictionary ID that can be resolved with the provided selector.

Methods inherited from interface org.apache.druid.query.monomorphicprocessing.HotLoopCallee

inspectRuntimeShape

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

classOfObject, getObject

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

getValueCardinality, idLookup, lookupName, lookupNameUtf8, nameLookupPossibleInAdvance, supportsLookupNameUtf8

Method Detail

getRow

@CalledFromHotLoop
IndexedInts getRow()

Returns the indexed values at the current position in this DimensionSelector. IMPORTANT. The returned IndexedInts object could generally be reused inside the implementation of DimensionSelector, i. e. this method could always return the same object for the same selector. Users of this API, such as Aggregator.aggregate(), BufferAggregator.aggregate(java.nio.ByteBuffer, int), AggregateCombiner.reset(org.apache.druid.segment.ColumnValueSelector), AggregateCombiner.fold(org.apache.druid.segment.ColumnValueSelector) should be prepared for that and not storing the object returned from this method in their state, assuming that the object will remain unchanged even when the position of the selector changes. This may not be the case.

makeValueMatcher

ValueMatcher makeValueMatcher(@Nullable
                              String value)

Parameters:

value - nullable dimension value

makeValueMatcher

ValueMatcher makeValueMatcher(com.google.common.base.Predicate<String> predicate)

getFloat

@Deprecated
default float getFloat()

Deprecated. This method is marked as deprecated in DimensionSelector to minimize the probability of accidental calling. "Polymorphism" of DimensionSelector should be used only when operating on ColumnValueSelector objects.

Specified by:

getFloat in interface BaseFloatColumnValueSelector

getDouble

@Deprecated
default double getDouble()

Deprecated. This method is marked as deprecated in DimensionSelector to minimize the probability of accidental calling. "Polymorphism" of DimensionSelector should be used only when operating on ColumnValueSelector objects.

Specified by:

getDouble in interface BaseDoubleColumnValueSelector

getLong

@Deprecated
default long getLong()

Deprecated. This method is marked as deprecated in DimensionSelector to minimize the probability of accidental calling. "Polymorphism" of DimensionSelector should be used only when operating on ColumnValueSelector objects.

Specified by:

getLong in interface BaseLongColumnValueSelector

isNull

@Deprecated
default boolean isNull()

Deprecated.

Description copied from interface: BaseNullableColumnValueSelector

Returns true if the primitive long, double, or float value returned by this selector should be treated as null. Users of BaseLongColumnValueSelector.getLong(), BaseDoubleColumnValueSelector.getDouble() and BaseFloatColumnValueSelector.getFloat() must check this method first, or else they may improperly use placeholder values returned by the primitive get methods. Users of BaseObjectColumnValueSelector.getObject() should not call this method. Instead, call "getObject" and check if it is null.

Specified by:

isNull in interface BaseNullableColumnValueSelector

defaultGetObject

@Nullable
default Object defaultGetObject()

Converts the current result of getRow() into null, if the row is empty, a String, if the row has size 1, or a String[] array, if the row has size > 1, using DimensionDictionarySelector.lookupName(int). This method is not the default implementation of BaseObjectColumnValueSelector.getObject() to minimize the chance that implementations "forget" to override it with more optimized version.

rowToObject

@Nullable
static Object rowToObject(IndexedInts row,
                                    DimensionDictionarySelector selector)

Converts a particular IndexedInts to an Object in a standard way, assuming each element in the IndexedInts is a dictionary ID that can be resolved with the provided selector.

nilSelector

static DimensionSelector nilSelector()

constant

static DimensionSelector constant(@Nullable
                                  String value)

constant

static DimensionSelector constant(@Nullable
                                  String value,
                                  @Nullable
                                  ExtractionFn extractionFn)

multiConstant

static DimensionSelector multiConstant(@Nullable
                                       List<String> values)

multiConstant

static DimensionSelector multiConstant(@Nullable
                                       List<String> values,
                                       @Nullable
                                       ExtractionFn extractionFn)

isNilSelector

static boolean isNilSelector(DimensionSelector selector)

Checks if the given selector constantly returns null. This method could be used in the beginning of execution of some queries and making some aggregations for heuristic shortcuts.