org.apache.druid.query.aggregation

Interface PostAggregator

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

Modifier and Type	Method and 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()
ValueType	getType() 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
ValueType getType()

Return the output type of a row processed with this post aggregator. Refer to the ValueType javadocs for details on the implications of choosing a type.

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>).