Class NonCollectingAggregator

All Implemented Interfaces:
Closeable, AutoCloseable,, Releasable
Direct Known Subclasses:

public abstract class NonCollectingAggregator extends AggregatorBase
An aggregator that is not collected, this can typically be used when running an aggregation over a field that doesn't have a mapping.
  • Constructor Details

  • Method Details

    • getLeafCollector

      public final LeafBucketCollector getLeafCollector(org.apache.lucene.index.LeafReaderContext reader, LeafBucketCollector sub)
      Description copied from class: AggregatorBase
      Collect results for this leaf.

      Most Aggregators will return a custom LeafBucketCollector that collects document information for every hit. Callers of this method will make sure to call collect for every hit. So any Aggregator that returns a customer LeafBucketCollector from this method runs at best O(hits) time. See the sum Aggregator for a fairly strait forward example of this.

      Some Aggregators are able to correctly collect results on their own, without being iterated by the top level query or the rest of the aggregations framework. These aggregations collect what they need by calling methods on LeafReaderContext and then they return LeafBucketCollector.NO_OP_COLLECTOR to signal that they've done their own collection. These aggregations can do better than O(hits). See the min Aggregator for an example of an aggregation that does this. It happens to run in constant time in some cases.

      In other cases MinAggregator can't get correct results by taking the constant time path so instead it returns a custom LeafBucketCollector. This is fairly common for aggregations that have these fast paths because most of these fast paths are only possible when the aggregation is at the root of the tree.

      Its also useful to look at the filters Aggregator chooses whether or not it can use the fast path before building the Aggregator rather than on each leaf. Either is fine.

      Specified by:
      getLeafCollector in class AggregatorBase
    • buildAggregations

      public InternalAggregation[] buildAggregations(long[] owningBucketOrds) throws IOException
      Description copied from class: Aggregator
      Build the results of this aggregation.
      Specified by:
      buildAggregations in class Aggregator
      owningBucketOrds - the ordinals of the buckets that we want to collect from this aggregation
      the results for each ordinal, in the same order as the array of ordinals