PostAggregator (druid-processing 28.0.1 API)

All Superinterfaces:

Cacheable

All Known Implementing Classes:

ArithmeticPostAggregator, ConstantPostAggregator, DoubleGreatestPostAggregator, DoubleLeastPostAggregator, ExpressionPostAggregator, FieldAccessPostAggregator, FinalizingFieldAccessPostAggregator, HyperUniqueFinalizingPostAggregator, JavaScriptPostAggregator, LongGreatestPostAggregator, LongLeastPostAggregator
```
public interface PostAggregator
extends Cacheable
```
Functionally similar to an Aggregator. See the Aggregator interface for more comments.

Method Summary

All Methods Instance Methods Abstract Methods Default Methods Deprecated Methods
Modifier and Type	Method	Description
`Object`	`compute(Map<String,Object> combinedAggregators)`
`PostAggregator`	`decorate(Map<String,AggregatorFactory> aggregators)`	Allows returning an enriched post aggregator, built from contextual information available from the given map of `AggregatorFactory` keyed by their names.
`Comparator`	`getComparator()`
`Set<String>`	`getDependentFields()`
`String`	`getName()`
`default ValueType`	`getType()`	Deprecated.
`default ColumnType`	`getType(ColumnInspector signature)`	Return the output type of a row processed with this post aggregator.

Methods inherited from interface org.apache.druid.java.util.common.Cacheable
getCacheKey

- Method Detail
  - getDependentFields
```
Set<String> getDependentFields()
```
  - getComparator
```
Comparator getComparator()
```
  - compute
```
@Nullable
Object compute(Map<String,Object> combinedAggregators)
```
  - getName
```
@Nullable
String getName()
```
  - getType
```
@Nullable
default ColumnType getType(ColumnInspector signature)
```
    Return the output type of a row processed with this post aggregator. Refer to the ColumnType javadocs for details on the implications of choosing a type.
    
    Parameters:
    
    signature -
  - getType
```
@Deprecated
default ValueType getType()
```
    Deprecated.
    
    This method is deprecated and will be removed soon. Use getType(ColumnInspector) instead. Do not call this method, it will likely produce incorrect results, it exists for backwards compatibility.
  - decorate
```
PostAggregator decorate(Map<String,AggregatorFactory> aggregators)
```
    Allows returning an enriched post aggregator, built from contextual information available from the given map of AggregatorFactory keyed by their names. Callers must call this method before calling compute(java.util.Map<java.lang.String, java.lang.Object>) or getComparator(). This is typically done in the constructor of queries which support post aggregators, via Queries.prepareAggregations(java.util.List<org.apache.druid.query.aggregation.AggregatorFactory>, java.util.List<org.apache.druid.query.aggregation.PostAggregator>).