org.apache.druid.segment

Interface DimensionSelector

All Superinterfaces:

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

All Known Subinterfaces:

HistoricalDimensionSelector, SingleValueHistoricalDimensionSelector

All Known Implementing Classes:

AbstractDimensionSelector, BaseSingleValueDimensionSelector, ConstantDimensionSelector, DoubleWrappingDimensionSelector, FloatWrappingDimensionSelector, LongWrappingDimensionSelector, SettableDimensionValueSelector, SingleScanTimeDimensionSelector, SingleStringInputDimensionSelector

public interface DimensionSelector
extends ColumnValueSelector<Object>, HotLoopCallee

Nested Class Summary

Nested Classes

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

Field Summary

Fields

Modifier and Type	Field and Description
static int	CARDINALITY_UNKNOWN

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

EMPTY_ARRAY

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 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.
int	getValueCardinality() Value cardinality is the cardinality of the different occurring values.
IdLookup	idLookup() Returns IdLookup if available for this DimensionSelector, or null.
static boolean	isNilSelector(DimensionSelector selector) Checks if the given selector constantly returns null.
default boolean	isNull() Deprecated.
String	lookupName(int id) The Name is the String name of the actual field.
ValueMatcher	makeValueMatcher(com.google.common.base.Predicate<String> predicate)
ValueMatcher	makeValueMatcher(String value)
boolean	nameLookupPossibleInAdvance() Returns true if it is possible to lookupName(int) by ids from 0 to getValueCardinality() before the rows with those ids are returned.

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

inspectRuntimeShape

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

classOfObject, getObject

Field Detail

CARDINALITY_UNKNOWN

static final int CARDINALITY_UNKNOWN

See Also:

Constant Field Values

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)

getValueCardinality

int getValueCardinality()

Value cardinality is the cardinality of the different occurring values. If there were 4 rows: A,B A B A Value cardinality would be 2. Cardinality may be unknown (e.g. the selector used by IncrementalIndex while reading input rows), in which case this method will return -1. If cardinality is unknown, you should assume this dimension selector has no dictionary, and avoid storing ids, calling "lookupId", or calling "lookupName" outside of the context of operating on a single row.

Returns:

the value cardinality, or -1 if unknown.

lookupName

@CalledFromHotLoop
 @Nullable
String lookupName(int id)

The Name is the String name of the actual field. It is assumed that storage layers convert names into id values which can then be used to get the string value. For example A,B A A,B B getRow() would return getRow(0) => [0 1] getRow(1) => [0] getRow(2) => [0 1] getRow(3) => [1] and then lookupName would return: lookupName(0) => A lookupName(1) => B

Parameters:

id - id to lookup the field name for

Returns:

the field name for the given id

nameLookupPossibleInAdvance

boolean nameLookupPossibleInAdvance()

Returns true if it is possible to lookupName(int) by ids from 0 to getValueCardinality() before the rows with those ids are returned.

Returns false if lookupName(int) could be called with ids, returned from the most recent call of getRow() on this DimensionSelector, but not earlier. If getValueCardinality() of this DimensionSelector additionally returns CARDINALITY_UNKNOWN, lookupName() couldn't be called with ids, returned by not the most recent call of getRow(), i. e. names for ids couldn't be looked up "later". If getValueCardinality() returns a non-negative number, lookupName() could be called with any ids, returned from #getRow() since the creation of this DimensionSelector.

If lookupName(int) is called with an ineligible id, result is undefined: exception could be thrown, or null returned, or some other random value.

idLookup

@Nullable
IdLookup idLookup()

Returns IdLookup if available for this DimensionSelector, or null.

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 selected primitive value is null for BaseFloatColumnValueSelector, BaseLongColumnValueSelector and BaseDoubleColumnValueSelector otherwise false.

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 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.

constant

static DimensionSelector constant(@Nullable
                                  String value)

constant

static DimensionSelector constant(@Nullable
                                  String value,
                                  @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.