Implemented makeAggregateCombiner() in ArrayOfDoublesSketchAggregatorFactory (#6093)

* implemented makeAggregateCombiner()

* test for makeAggregateCombiner()

* license, style fix

extensions-core/datasketches/src/main/java/io/druid/query/aggregation/datasketches/tuple/ArrayOfDoublesSketchAggregatorFactory.java

@@ -32,15 +32,18 @@ import com.fasterxml.jackson.annotation.JsonProperty;
 import com.google.common.base.Preconditions;
 
 import io.druid.java.util.common.IAE;
+import io.druid.query.aggregation.AggregateCombiner;
 import io.druid.query.aggregation.Aggregator;
 import io.druid.query.aggregation.AggregatorFactory;
 import io.druid.query.aggregation.AggregatorUtil;
 import io.druid.query.aggregation.BufferAggregator;
+import io.druid.query.aggregation.ObjectAggregateCombiner;
 import io.druid.query.cache.CacheKeyBuilder;
 import io.druid.query.dimension.DefaultDimensionSpec;
 import io.druid.segment.BaseDoubleColumnValueSelector;
 import io.druid.segment.BaseObjectColumnValueSelector;
 import io.druid.segment.ColumnSelectorFactory;
+import io.druid.segment.ColumnValueSelector;
 import io.druid.segment.DimensionSelector;
 import io.druid.segment.DimensionSelectorUtils;
 import io.druid.segment.NilColumnValueSelector;
@@ -173,6 +176,42 @@ public class ArrayOfDoublesSketchAggregatorFactory extends AggregatorFactory
     return union.getResult();
   }
 
+  @Override
+  public AggregateCombiner makeAggregateCombiner()
+  {
+    return new ObjectAggregateCombiner<ArrayOfDoublesSketch>()
+    {
+      private final ArrayOfDoublesUnion union = new ArrayOfDoublesSetOperationBuilder().setNominalEntries(nominalEntries)
+          .setNumberOfValues(numberOfValues).buildUnion();
+
+      @Override
+      public void reset(final ColumnValueSelector selector)
+      {
+        union.reset();
+        fold(selector);
+      }
+
+      @Override
+      public void fold(final ColumnValueSelector selector)
+      {
+        final ArrayOfDoublesSketch sketch = (ArrayOfDoublesSketch) selector.getObject();
+        union.update(sketch);
+      }
+
+      @Override
+      public ArrayOfDoublesSketch getObject()
+      {
+        return union.getResult();
+      }
+
+      @Override
+      public Class<ArrayOfDoublesSketch> classOfObject()
+      {
+        return ArrayOfDoublesSketch.class;
+      }
+    };
+  }
+  
   @Override
   @JsonProperty
   public String getName()

extensions-core/datasketches/src/test/java/io/druid/query/aggregation/datasketches/tuple/ArrayOfDoublesSketchAggregatorFactoryTest.java

@@ -0,0 +1,60 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+package io.druid.query.aggregation.datasketches.tuple;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+import com.yahoo.sketches.tuple.ArrayOfDoublesSketch;
+import com.yahoo.sketches.tuple.ArrayOfDoublesUpdatableSketch;
+import com.yahoo.sketches.tuple.ArrayOfDoublesUpdatableSketchBuilder;
+
+import io.druid.query.aggregation.AggregateCombiner;
+import io.druid.query.aggregation.AggregatorFactory;
+import io.druid.query.aggregation.TestObjectColumnSelector;
+
+public class ArrayOfDoublesSketchAggregatorFactoryTest
+{
+
+  @Test
+  public void makeAggregateCombiner()
+  {
+    AggregatorFactory aggregatorFactory = new ArrayOfDoublesSketchAggregatorFactory("", "", null, null, null);
+    AggregatorFactory combiningFactory = aggregatorFactory.getCombiningFactory();
+    AggregateCombiner<ArrayOfDoublesSketch> combiner = combiningFactory.makeAggregateCombiner();
+
+    ArrayOfDoublesUpdatableSketch sketch1 = new ArrayOfDoublesUpdatableSketchBuilder().build();
+    sketch1.update("a", new double[] {1});
+
+    ArrayOfDoublesUpdatableSketch sketch2 = new ArrayOfDoublesUpdatableSketchBuilder().build();
+    sketch2.update("b", new double[] {1});
+    sketch2.update("c", new double[] {1});
+
+    TestObjectColumnSelector<ArrayOfDoublesSketch> selector = new TestObjectColumnSelector<ArrayOfDoublesSketch>(new ArrayOfDoublesSketch[] {sketch1, sketch2});
+
+    combiner.reset(selector);
+    Assert.assertEquals(1, combiner.getObject().getEstimate(), 0);
+
+    selector.increment();
+    combiner.fold(selector);
+    Assert.assertEquals(3, combiner.getObject().getEstimate(), 0);
+  }
+
+}