Package org.apache.druid.query.aggregation

Class HistogramAggregatorFactory

java.lang.Object
org.apache.druid.query.aggregation.AggregatorFactory
org.apache.druid.query.aggregation.HistogramAggregatorFactory
All Implemented Interfaces:
Cacheable
public class HistogramAggregatorFactory extends AggregatorFactory

  • Field Details

    • TYPE

      public static final ColumnType TYPE

    • TYPE_VISUAL

      public static final ColumnType TYPE_VISUAL

  • Constructor Details

    • HistogramAggregatorFactory

      public HistogramAggregatorFactory(String name, String fieldName, List<Float> breaksList)

  • Method Details

    • 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

      public Object combine(Object lhs, Object rhs)
      Description copied from class: AggregatorFactory
      A method that knows how to combine the outputs of Aggregator.get() produced via AggregatorFactory.factorize(org.apache.druid.segment.ColumnSelectorFactory) or BufferAggregator.get(java.nio.ByteBuffer, int) produced via AggregatorFactory.factorizeBuffered(org.apache.druid.segment.ColumnSelectorFactory). Note, even though this method 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 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

    • makeAggregateCombiner

      public AggregateCombiner makeAggregateCombiner()
      Description copied from class: AggregatorFactory
      Creates an AggregateCombiner to fold rollup aggregation results from serveral "rows" of different indexes during index merging. AggregateCombiner implements the same logic as AggregatorFactory.combine(java.lang.Object, java.lang.Object), with the difference that it uses ColumnValueSelector and it's subinterfaces to get inputs and implements ColumnValueSelector to provide output.
      Overrides:
      makeAggregateCombiner in class AggregatorFactory
      See Also:

    • 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

    • getName

      public String getName()
      Specified by:
      getName in class AggregatorFactory
      Returns:
      output name of the aggregator column.

    • getFieldName

      public String getFieldName()

    • getBreaks

      public List<Float> getBreaks()

    • 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

    • getCacheKey

      public byte[] getCacheKey()
      Description copied from interface: Cacheable
      Get a byte array used as a cache key.
      Returns:
      bytes to be used as cache key - or null if this object should not be cached.

    • getIntermediateType

      public ColumnType getIntermediateType()
      actual type is Histogram
      Overrides:
      getIntermediateType in class AggregatorFactory

    • getResultType

      public ColumnType getResultType()
      actual type is HistogramVisual
      Overrides:
      getResultType 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.

    • withName

      public AggregatorFactory withName(String newName)
      Description copied from class: AggregatorFactory
      Used in cases where we want to change the output name of the aggregator to something else. For eg: if we have a query `select a, sum(b) as total group by a from table` the aggregator returned from the native group by query is "a0" set in org.apache.druid.sql.calcite.rel.DruidQuery#computeAggregations. We can use withName("total") to set the output name of the aggregator to "total".

      As all implementations of this interface method may not exist, callers of this method are advised to handle such a case.

      Overrides:
      withName in class AggregatorFactory
      Parameters:
      newName - newName of the output for aggregator factory
      Returns:
      AggregatorFactory with the output name set as the input param.

    • toString

      public String toString()
      Overrides:
      toString in class Object

    • equals

      public boolean equals(Object o)
      Overrides:
      equals in class Object

    • hashCode

      public int hashCode()
      Overrides:
      hashCode in class Object