Package org.elasticsearch.search.aggregations.bucket.nested

Class NestedAggregator

java.lang.Object
org.elasticsearch.search.aggregations.BucketCollector
org.elasticsearch.search.aggregations.Aggregator
org.elasticsearch.search.aggregations.AggregatorBase
org.elasticsearch.search.aggregations.bucket.BucketsAggregator
org.elasticsearch.search.aggregations.bucket.nested.NestedAggregator
All Implemented Interfaces:
Closeable, AutoCloseable, org.apache.lucene.search.Collector, org.elasticsearch.core.Releasable, SingleBucketAggregator
public class NestedAggregator extends BucketsAggregator implements SingleBucketAggregator

  • Method Details

    • getLeafCollector

      public LeafBucketCollector getLeafCollector(org.apache.lucene.index.LeafReaderContext ctx, LeafBucketCollector sub) throws IOException
      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
      Throws:
      IOException

    • preGetSubLeafCollectors

      protected void preGetSubLeafCollectors(org.apache.lucene.index.LeafReaderContext ctx) throws IOException
      Description copied from class: AggregatorBase
      Can be overridden by aggregator implementations that like the perform an operation before the leaf collectors of children aggregators are instantiated for the next segment.
      Overrides:
      preGetSubLeafCollectors in class BucketsAggregator
      Throws:
      IOException

    • doPostCollection

      protected void doPostCollection() throws IOException
      Description copied from class: AggregatorBase
      Can be overridden by aggregator implementation to be called back when the collection phase ends.
      Overrides:
      doPostCollection in class AggregatorBase
      Throws:
      IOException

    • 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
      Parameters:
      owningBucketOrds - the ordinals of the buckets that we want to collect from this aggregation
      Returns:
      the results for each ordinal, in the same order as the array of ordinals
      Throws:
      IOException

    • buildEmptyAggregation

      public InternalAggregation buildEmptyAggregation()
      Description copied from class: Aggregator
      Build an empty aggregation.
      Specified by:
      buildEmptyAggregation in class Aggregator