java.lang.Object
- org.apache.druid.query.aggregation.AggregatorFactory
- - org.apache.druid.query.aggregation.SingleValueAggregatorFactory

All Implemented Interfaces:

Cacheable
```
public class SingleValueAggregatorFactory
extends AggregatorFactory
```
This AggregatorFactory is meant to wrap the subquery used as an expression into a single value and is expected to throw an exception when the subquery results in more than one row
This consumes columnType as well along with name and fieldName to pass it on to underlying SingleValueBufferAggregator to work with different ColumnTypes

Field Summary

Fields
Modifier and Type Field Description

static int DEFAULT_MAX_VALUE_SIZE

Constructor Summary

Constructors
Constructor Description

SingleValueAggregatorFactory(String name, String fieldName, ColumnType columnType)

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method	Description
`Object`	`combine(Object lhs, Object rhs)`	Combine method would never be invoked as the broker sends the subquery to multiple segments and gather the results to a single value on which the single value aggregator is applied.
`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)`
`Aggregator`	`factorize(ColumnSelectorFactory metricFactory)`
`BufferAggregator`	`factorizeBuffered(ColumnSelectorFactory metricFactory)`
`Object`	`finalizeComputation(Object object)`	"Finalizes" the computation of an object.
`byte[]`	`getCacheKey()`	Get a byte array used as a cache key.
`AggregatorFactory`	`getCombiningFactory()`	Returns an AggregatorFactory that can be used to combine the output of aggregators from this factory.
`Comparator`	`getComparator()`
`String`	`getFieldName()`
`ColumnType`	`getIntermediateType()`	Get the "intermediate" `ColumnType` for this aggregator.
`int`	`getMaxIntermediateSize()`	Returns the maximum size that this aggregator will require in bytes for intermediate storage of results.
`String`	`getName()`
`ColumnType`	`getResultType()`	Get the `ColumnType` for the final form of this aggregator, i.e.
`int`	`hashCode()`
`List<String>`	`requiredFields()`	Get a list of fields that aggregators built by this factory will need to read.
`String`	`toString()`

Methods inherited from class org.apache.druid.query.aggregation.AggregatorFactory
canVectorize, factorizeVector, factorizeWithSize, getComplexTypeName, getFinalizedType, getMaxIntermediateSizeWithNulls, getMergingFactory, getRequiredColumns, getType, guessAggregatorHeapFootprint, makeAggregateCombiner, makeNullableAggregateCombiner, mergeAggregators, optimizeForSegment, substituteCombiningFactory, withName

Methods inherited from class java.lang.Object
clone, finalize, getClass, notify, notifyAll, wait, wait, wait

- Field Detail
  - DEFAULT_MAX_VALUE_SIZE
```
public static final int DEFAULT_MAX_VALUE_SIZE
```
    See Also:
    
    Constant Field Values
- Constructor Detail
  - SingleValueAggregatorFactory
```
public SingleValueAggregatorFactory(String name,
                                    String fieldName,
                                    ColumnType columnType)
```
- Method Detail
  - factorize
```
public Aggregator factorize(ColumnSelectorFactory metricFactory)
```
    Specified by:
    
    factorize in class AggregatorFactory
  - factorizeBuffered
```
public BufferAggregator factorizeBuffered(ColumnSelectorFactory metricFactory)
```
    Specified by:
    
    factorizeBuffered in class AggregatorFactory
  - getComparator
```
public Comparator getComparator()
```
    Specified by:
    
    getComparator in class AggregatorFactory
  - combine
```
@Nullable
public Object combine(@Nullable
                      Object lhs,
                      @Nullable
                      Object rhs)
```
    Combine method would never be invoked as the broker sends the subquery to multiple segments and gather the results to a single value on which the single value aggregator is applied. Though getCombiningFactory would be invoked for understanding the fieldname.
    
    Specified by:
    
    combine in class 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 class: AggregatorFactory
    
    Returns an AggregatorFactory that can be used to combine the output of aggregators from this factory. It is used when we know we have some values that were produced with this aggregator factory, and want to do some additional combining of them. This happens, for example, when merging query results from two different segments, or two different servers. For simple aggregators, the combining factory may be computed by 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. For example, this aggregator: {"type": "longSum", "fieldName": "foo", "name": "bar"} Would become: {"type": "longSum", "fieldName": "bar", "name": "bar"} Sometimes, the type or other parameters of the combining aggregator will be different from the original aggregator. For example, the CountAggregatorFactory getCombiningFactory method will return a LongSumAggregatorFactory, because counts are combined by summing. No matter what, `foo.getCombiningFactory()` and `foo.getCombiningFactory().getCombiningFactory()` should return the same result.
    
    Specified by:
    
    getCombiningFactory in class AggregatorFactory
    
    Returns:
    
    a new Factory that can be used for operations on top of data output from the current factory.
  - deserialize
```
public Object deserialize(Object object)
```
    Description copied from class: 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 class AggregatorFactory
    
    Parameters:
    
    object - the object to deserialize
    
    Returns:
    
    the deserialized object
  - finalizeComputation
```
@Nullable
public Object finalizeComputation(@Nullable
                                  Object object)
```
    Description copied from class: 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 class AggregatorFactory
    
    Parameters:
    
    object - the object to be finalized
    
    Returns:
    
    the finalized value that should be returned for the initial query
  - getIntermediateType
```
public ColumnType getIntermediateType()
```
    Description copied from class: AggregatorFactory
    
    Get the "intermediate" ColumnType for this aggregator. This is the same as the type returned by AggregatorFactory.deserialize(java.lang.Object) and the type accepted by AggregatorFactory.combine(java.lang.Object, java.lang.Object). However, it is *not* necessarily the same type returned by AggregatorFactory.finalizeComputation(java.lang.Object). Refer to the ColumnType javadocs for details on the implications of choosing a type.
    
    Overrides:
    
    getIntermediateType in class AggregatorFactory
  - getResultType
```
public ColumnType getResultType()
```
    Description copied from class: AggregatorFactory
    
    Get the ColumnType for the final form of this aggregator, i.e. the type of the value returned by AggregatorFactory.finalizeComputation(java.lang.Object). This may be the same as or different than the types expected in AggregatorFactory.deserialize(java.lang.Object) and AggregatorFactory.combine(java.lang.Object, java.lang.Object). Refer to the ColumnType javadocs for details on the implications of choosing a type.
    
    Overrides:
    
    getResultType in class AggregatorFactory
  - getName
```
public String getName()
```
    Specified by:
    
    getName in class AggregatorFactory
    
    Returns:
    
    output name of the aggregator column.
  - getFieldName
```
public String getFieldName()
```
  - requiredFields
```
public List<String> requiredFields()
```
    Description copied from class: AggregatorFactory
    
    Get a list of fields that aggregators built by this factory will need to read.
    
    Specified by:
    
    requiredFields in class AggregatorFactory
  - getMaxIntermediateSize
```
public int getMaxIntermediateSize()
```
    Description copied from class: AggregatorFactory
    
    Returns the maximum size that this aggregator will require in bytes for intermediate storage of results.
    
    Specified by:
    
    getMaxIntermediateSize in class AggregatorFactory
    
    Returns:
    
    the maximum number of bytes that an aggregator of this type will require for intermediate result storage.
  - getCacheKey
```
public byte[] getCacheKey()
```
    Description copied from interface: Cacheable
    
    Get a byte array used as a cache key.
    
    Returns:
    
    a cache key
  - 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

Class SingleValueAggregatorFactory

Field Summary

Constructor Summary

Method Summary

Methods inherited from class org.apache.druid.query.aggregation.AggregatorFactory

Methods inherited from class java.lang.Object

Field Detail

DEFAULT_MAX_VALUE_SIZE

Constructor Detail

SingleValueAggregatorFactory

Method Detail

factorize

factorizeBuffered

getComparator

combine

getCombiningFactory

deserialize

finalizeComputation

getIntermediateType

getResultType

getName

getFieldName

requiredFields

getMaxIntermediateSize

getCacheKey

equals

hashCode

toString