org.apache.druid.segment

Class ConstantDimensionSelector

java.lang.Object

org.apache.druid.segment.ConstantDimensionSelector

All Implemented Interfaces:

HotLoopCallee, BaseDoubleColumnValueSelector, BaseFloatColumnValueSelector, BaseLongColumnValueSelector, BaseNullableColumnValueSelector, BaseObjectColumnValueSelector<Object>, ColumnValueSelector<Object>, DimensionSelector, HistoricalDimensionSelector, SingleValueHistoricalDimensionSelector, IdLookup

public class ConstantDimensionSelector
extends Object
implements SingleValueHistoricalDimensionSelector, IdLookup

Nested Class Summary

Nested classes/interfaces inherited from interface org.apache.druid.segment.DimensionSelector

DimensionSelector.NullDimensionSelectorHolder

Field Summary

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

CARDINALITY_UNKNOWN

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

EMPTY_ARRAY

Method Summary

Modifier and Type	Method and Description
Class	classOfObject()
Object	getObject()
IndexedInts	getRow() Returns the indexed values at the current position in this DimensionSelector.
IndexedInts	getRow(int offset)
int	getRowValue(int offset)
int	getValueCardinality() Value cardinality is the cardinality of the different occurring values.
IdLookup	idLookup() Returns IdLookup if available for this DimensionSelector, or null.
void	inspectRuntimeShape(RuntimeShapeInspector inspector) Implementations of this method should call inspector.visit() with all fields of this class, which meet two conditions: 1.
int	lookupId(String name) Inverse of DimensionSelector.lookupName(int).
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 matchValue)
boolean	nameLookupPossibleInAdvance() Returns true if it is possible to DimensionSelector.lookupName(int) by ids from 0 to DimensionSelector.getValueCardinality() before the rows with those ids are returned.

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.segment.DimensionSelector

constant, constant, defaultGetObject, getDouble, getFloat, getLong, isNilSelector, isNull

Method Detail

getRow

public IndexedInts getRow()

Description copied from interface: DimensionSelector

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.

Specified by:

getRow in interface DimensionSelector

getRowValue

public int getRowValue(int offset)

Specified by:

getRowValue in interface SingleValueHistoricalDimensionSelector

getRow

public IndexedInts getRow(int offset)

Specified by:

getRow in interface HistoricalDimensionSelector

makeValueMatcher

public ValueMatcher makeValueMatcher(String matchValue)

Specified by:

makeValueMatcher in interface DimensionSelector

Parameters:

matchValue - nullable dimension value

makeValueMatcher

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

Specified by:

makeValueMatcher in interface DimensionSelector

getValueCardinality

public int getValueCardinality()

Description copied from interface: DimensionSelector

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.

Specified by:

getValueCardinality in interface DimensionSelector

Returns:

the value cardinality, or -1 if unknown.

lookupName

public String lookupName(int id)

Description copied from interface: DimensionSelector

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

Specified by:

lookupName in interface DimensionSelector

Parameters:

id - id to lookup the field name for

Returns:

the field name for the given id

nameLookupPossibleInAdvance

public boolean nameLookupPossibleInAdvance()

Description copied from interface: DimensionSelector

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

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

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

Specified by:

nameLookupPossibleInAdvance in interface DimensionSelector

idLookup

@Nullable
public IdLookup idLookup()

Description copied from interface: DimensionSelector

Returns IdLookup if available for this DimensionSelector, or null.

Specified by:

idLookup in interface DimensionSelector

lookupId

public int lookupId(String name)

Description copied from interface: IdLookup

Inverse of DimensionSelector.lookupName(int).

Specified by:

lookupId in interface IdLookup

getObject

@Nullable
public Object getObject()

Specified by:

getObject in interface BaseObjectColumnValueSelector<Object>

classOfObject

public Class classOfObject()

Specified by:

classOfObject in interface BaseObjectColumnValueSelector<Object>

inspectRuntimeShape

public void inspectRuntimeShape(RuntimeShapeInspector inspector)

Description copied from interface: HotLoopCallee

Implementations of this method should call inspector.visit() with all fields of this class, which meet two conditions: 1. They are used in methods of this class, annotated with CalledFromHotLoop 2. They are either: a. Nullable objects b. Instances of HotLoopCallee c. Objects, which don't always have a specific class in runtime. For example, a field of type Set could be HashSet or TreeSet in runtime, depending on how this instance (the instance on which inspectRuntimeShape() is called) is configured. d. ByteBuffer or similar objects, where byte order matters e. boolean flags, affecting branch taking f. Arrays of objects, meeting any of conditions a-e.

Specified by:

inspectRuntimeShape in interface HotLoopCallee