Make InternalCentroid leaner (#116302)

We are currently holding to fields to extract values, this commit makes them abstract methods so 
we don't use any heap.

server/src/main/java/org/elasticsearch/search/aggregations/metrics/InternalCentroid.java

@@ -23,32 +23,20 @@
 import java.util.List;
 import java.util.Map;
 import java.util.Objects;
-import java.util.function.Function;
 
 /**
  * Serialization and merge logic for {@link GeoCentroidAggregator}.
  */
 public abstract class InternalCentroid extends InternalAggregation implements CentroidAggregation {
     protected final SpatialPoint centroid;
     protected final long count;
-    private final FieldExtractor firstField;
-    private final FieldExtractor secondField;
-
-    public InternalCentroid(
-        String name,
-        SpatialPoint centroid,
-        long count,
-        Map<String, Object> metadata,
-        FieldExtractor firstField,
-        FieldExtractor secondField
-    ) {
+
+    public InternalCentroid(String name, SpatialPoint centroid, long count, Map<String, Object> metadata) {
         super(name, metadata);
         assert (centroid == null) == (count == 0);
         this.centroid = centroid;
         assert count >= 0;
         this.count = count;
-        this.firstField = firstField;
-        this.secondField = secondField;
     }
 
     protected abstract SpatialPoint centroidFromStream(StreamInput in) throws IOException;
@@ -59,16 +47,14 @@ public InternalCentroid(
      * Read from a stream.
      */
     @SuppressWarnings("this-escape")
-    protected InternalCentroid(StreamInput in, FieldExtractor firstField, FieldExtractor secondField) throws IOException {
+    protected InternalCentroid(StreamInput in) throws IOException {
         super(in);
         count = in.readVLong();
         if (in.readBoolean()) {
             centroid = centroidFromStream(in);
         } else {
             centroid = null;
         }
-        this.firstField = firstField;
-        this.secondField = secondField;
     }
 
     @Override
@@ -110,11 +96,11 @@ public void accept(InternalAggregation aggregation) {
                 if (centroidAgg.count > 0) {
                     totalCount += centroidAgg.count;
                     if (Double.isNaN(firstSum)) {
-                        firstSum = centroidAgg.count * firstField.extractor.apply(centroidAgg.centroid);
-                        secondSum = centroidAgg.count * secondField.extractor.apply(centroidAgg.centroid);
+                        firstSum = centroidAgg.count * extractFirst(centroidAgg.centroid);
+                        secondSum = centroidAgg.count * extractSecond(centroidAgg.centroid);
                     } else {
-                        firstSum += centroidAgg.count * firstField.extractor.apply(centroidAgg.centroid);
-                        secondSum += centroidAgg.count * secondField.extractor.apply(centroidAgg.centroid);
+                        firstSum += centroidAgg.count * extractFirst(centroidAgg.centroid);
+                        secondSum += centroidAgg.count * extractSecond(centroidAgg.centroid);
                     }
                 }
             }
@@ -126,6 +112,14 @@ public InternalAggregation get() {
         };
     }
 
+    protected abstract String nameFirst();
+
+    protected abstract double extractFirst(SpatialPoint point);
+
+    protected abstract String nameSecond();
+
+    protected abstract double extractSecond(SpatialPoint point);
+
     @Override
     public InternalAggregation finalizeSampling(SamplingContext samplingContext) {
         return copyWith(centroid, samplingContext.scaleUp(count));
@@ -136,16 +130,6 @@ protected boolean mustReduceOnSingleInternalAgg() {
         return false;
     }
 
-    protected static class FieldExtractor {
-        private final String name;
-        private final Function<SpatialPoint, Double> extractor;
-
-        public FieldExtractor(String name, Function<SpatialPoint, Double> extractor) {
-            this.name = name;
-            this.extractor = extractor;
-        }
-    }
-
     protected abstract double extractDouble(String name);
 
     @Override
@@ -174,8 +158,8 @@ public XContentBuilder doXContentBody(XContentBuilder builder, Params params) th
         if (centroid != null) {
             builder.startObject(Fields.CENTROID.getPreferredName());
             {
-                builder.field(firstField.name, firstField.extractor.apply(centroid));
-                builder.field(secondField.name, secondField.extractor.apply(centroid));
+                builder.field(nameFirst(), extractFirst(centroid));
+                builder.field(nameSecond(), extractSecond(centroid));
             }
             builder.endObject();
         }

server/src/main/java/org/elasticsearch/search/aggregations/metrics/InternalGeoCentroid.java

@@ -15,7 +15,6 @@
 import org.elasticsearch.common.io.stream.StreamOutput;
 import org.elasticsearch.search.aggregations.InternalAggregation;
 import org.elasticsearch.search.aggregations.support.SamplingContext;
-import org.elasticsearch.xcontent.ParseField;
 
 import java.io.IOException;
 import java.util.Map;
@@ -26,21 +25,14 @@
 public class InternalGeoCentroid extends InternalCentroid implements GeoCentroid {
 
     public InternalGeoCentroid(String name, SpatialPoint centroid, long count, Map<String, Object> metadata) {
-        super(
-            name,
-            centroid,
-            count,
-            metadata,
-            new FieldExtractor("lat", SpatialPoint::getY),
-            new FieldExtractor("lon", SpatialPoint::getX)
-        );
+        super(name, centroid, count, metadata);
     }
 
     /**
      * Read from a stream.
      */
     public InternalGeoCentroid(StreamInput in) throws IOException {
-        super(in, new FieldExtractor("lat", SpatialPoint::getY), new FieldExtractor("lon", SpatialPoint::getX));
+        super(in);
     }
 
     public static InternalGeoCentroid empty(String name, Map<String, Object> metadata) {
@@ -84,12 +76,27 @@ protected InternalGeoCentroid copyWith(double firstSum, double secondSum, long t
     }
 
     @Override
-    public InternalAggregation finalizeSampling(SamplingContext samplingContext) {
-        return new InternalGeoCentroid(name, centroid, samplingContext.scaleUp(count), getMetadata());
+    protected String nameFirst() {
+        return "lat";
+    }
+
+    @Override
+    protected double extractFirst(SpatialPoint point) {
+        return point.getY();
+    }
+
+    @Override
+    protected String nameSecond() {
+        return "lon";
+    }
+
+    @Override
+    protected double extractSecond(SpatialPoint point) {
+        return point.getX();
     }
 
-    static class Fields {
-        static final ParseField CENTROID_LAT = new ParseField("lat");
-        static final ParseField CENTROID_LON = new ParseField("lon");
+    @Override
+    public InternalAggregation finalizeSampling(SamplingContext samplingContext) {
+        return new InternalGeoCentroid(name, centroid, samplingContext.scaleUp(count), getMetadata());
     }
 }

x-pack/plugin/spatial/src/main/java/org/elasticsearch/xpack/spatial/search/aggregations/metrics/InternalCartesianCentroid.java

@@ -13,7 +13,6 @@
 import org.elasticsearch.search.aggregations.InternalAggregation;
 import org.elasticsearch.search.aggregations.metrics.InternalCentroid;
 import org.elasticsearch.search.aggregations.support.SamplingContext;
-import org.elasticsearch.xcontent.ParseField;
 import org.elasticsearch.xpack.spatial.common.CartesianPoint;
 
 import java.io.IOException;
@@ -25,14 +24,14 @@
 public class InternalCartesianCentroid extends InternalCentroid implements CartesianCentroid {
 
     public InternalCartesianCentroid(String name, SpatialPoint centroid, long count, Map<String, Object> metadata) {
-        super(name, centroid, count, metadata, new FieldExtractor("x", SpatialPoint::getX), new FieldExtractor("y", SpatialPoint::getY));
+        super(name, centroid, count, metadata);
     }
 
     /**
      * Read from a stream.
      */
     public InternalCartesianCentroid(StreamInput in) throws IOException {
-        super(in, new FieldExtractor("x", SpatialPoint::getX), new FieldExtractor("y", SpatialPoint::getY));
+        super(in);
     }
 
     @Override
@@ -80,8 +79,23 @@ public InternalAggregation finalizeSampling(SamplingContext samplingContext) {
         return new InternalCartesianCentroid(name, centroid, samplingContext.scaleUp(count), getMetadata());
     }
 
-    static class Fields {
-        static final ParseField CENTROID_X = new ParseField("x");
-        static final ParseField CENTROID_Y = new ParseField("y");
+    @Override
+    protected String nameFirst() {
+        return "x";
+    }
+
+    @Override
+    protected double extractFirst(SpatialPoint point) {
+        return point.getX();
+    }
+
+    @Override
+    protected String nameSecond() {
+        return "y";
+    }
+
+    @Override
+    protected double extractSecond(SpatialPoint point) {
+        return point.getY();
     }
 }