io.druid.query.aggregation.cardinality

Class CardinalityAggregatorFactory

java.lang.Object

io.druid.query.aggregation.cardinality.CardinalityAggregatorFactory

All Implemented Interfaces:

AggregatorFactory

public class CardinalityAggregatorFactory
extends Object
implements AggregatorFactory

Constructor Summary

Constructors

Constructor and Description
CardinalityAggregatorFactory(String name, List<String> fieldNames, boolean byRow)

Method Summary

Methods

Modifier and Type	Method and Description
Object	combine(Object lhs, Object rhs) A method that knows how to combine the outputs of the getIntermediate() method from the Aggregators produced via factorize().
Object	deserialize(Object object) A method that knows how to "deserialize" the object from whatever form it might have been put into in order to transfer via JSON.
boolean	equals(Object o)
static Object	estimateCardinality(Object object)
Aggregator	factorize(ColumnSelectorFactory columnFactory)
BufferAggregator	factorizeBuffered(ColumnSelectorFactory columnFactory)
Object	finalizeComputation(Object object) "Finalizes" the computation of an object.
Object	getAggregatorStartValue() Returns the starting value for a corresponding aggregator.
byte[]	getCacheKey()
AggregatorFactory	getCombiningFactory() Returns an AggregatorFactory that can be used to combine the output of aggregators from this factory.
Comparator	getComparator()
List<String>	getFieldNames()
int	getMaxIntermediateSize() Returns the maximum size that this aggregator will require in bytes for intermediate storage of results.
String	getName()
List<AggregatorFactory>	getRequiredColumns() Gets a list of all columns that this AggregatorFactory will scan
String	getTypeName()
int	hashCode()
boolean	isByRow()
List<String>	requiredFields()
String	toString()

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Constructor Detail

CardinalityAggregatorFactory

public CardinalityAggregatorFactory(String name,
                            List<String> fieldNames,
                            boolean byRow)

Method Detail

estimateCardinality

public static Object estimateCardinality(Object object)

factorize

public Aggregator factorize(ColumnSelectorFactory columnFactory)

Specified by:

factorize in interface AggregatorFactory

factorizeBuffered

public BufferAggregator factorizeBuffered(ColumnSelectorFactory columnFactory)

Specified by:

factorizeBuffered in interface AggregatorFactory

getComparator

public Comparator getComparator()

Specified by:

getComparator in interface AggregatorFactory

combine

public Object combine(Object lhs,
             Object rhs)

Description copied from interface: AggregatorFactory

A method that knows how to combine the outputs of the getIntermediate() method from the Aggregators produced via factorize(). Note, even though this is called combine, this method's contract *does* allow for mutation of the input objects. Thus, any use of lhs or rhs after calling this method is highly discouraged.

Specified by:

combine in interface AggregatorFactory

Parameters:

lhs - The left hand side of the combine

rhs - The right hand side of the combine

Returns:

an object representing the combination of lhs and rhs, this can be a new object or a mutation of the inputs

getCombiningFactory

public AggregatorFactory getCombiningFactory()

Description copied from interface: AggregatorFactory

Returns an AggregatorFactory that can be used to combine the output of aggregators from this factory. This generally amounts to simply creating a new factory that is the same as the current except with its input column renamed to the same as the output column.

Specified by:

getCombiningFactory in interface AggregatorFactory

Returns:

a new Factory that can be used for operations on top of data output from the current factory.

getRequiredColumns

public List<AggregatorFactory> getRequiredColumns()

Description copied from interface: AggregatorFactory

Gets a list of all columns that this AggregatorFactory will scan

Specified by:

getRequiredColumns in interface AggregatorFactory

Returns:

AggregatorFactories for the columns to scan of the parent AggregatorFactory

deserialize

public Object deserialize(Object object)

Description copied from interface: AggregatorFactory

A method that knows how to "deserialize" the object from whatever form it might have been put into in order to transfer via JSON.

Specified by:

deserialize in interface AggregatorFactory

Parameters:

object - the object to deserialize

Returns:

the deserialized object

finalizeComputation

public Object finalizeComputation(Object object)

Description copied from interface: AggregatorFactory

"Finalizes" the computation of an object. Primarily useful for complex types that have a different mergeable intermediate format than their final resultant output.

Specified by:

finalizeComputation in interface AggregatorFactory

Parameters:

object - the object to be finalized

Returns:

the finalized value that should be returned for the initial query

getName

public String getName()

Specified by:

getName in interface AggregatorFactory

requiredFields

public List<String> requiredFields()

Specified by:

requiredFields in interface AggregatorFactory

getFieldNames

public List<String> getFieldNames()

isByRow

public boolean isByRow()

getCacheKey

public byte[] getCacheKey()

Specified by:

getCacheKey in interface AggregatorFactory

getTypeName

public String getTypeName()

Specified by:

getTypeName in interface AggregatorFactory

getMaxIntermediateSize

public int getMaxIntermediateSize()

Description copied from interface: AggregatorFactory

Returns the maximum size that this aggregator will require in bytes for intermediate storage of results.

Specified by:

getMaxIntermediateSize in interface AggregatorFactory

Returns:

the maximum number of bytes that an aggregator of this type will require for intermediate result storage.

getAggregatorStartValue

public Object getAggregatorStartValue()

Description copied from interface: AggregatorFactory

Returns the starting value for a corresponding aggregator. For example, 0 for sums, - Infinity for max, an empty mogrifier

Specified by:

getAggregatorStartValue in interface AggregatorFactory

Returns:

the starting value for a corresponding aggregator.

equals

public boolean equals(Object o)

Overrides:

equals in class Object

hashCode

public int hashCode()

Overrides:

hashCode in class Object

toString

public String toString()

Overrides:

toString in class Object