Wire Cardinality aggregation to work with the ValuesSourceRegistry

server/src/main/java/org/elasticsearch/search/SearchModule.java

@@ -358,7 +358,8 @@ private void registerAggregations(List<SearchPlugin> plugins) {
                 MedianAbsoluteDeviationAggregationBuilder::new, MedianAbsoluteDeviationAggregationBuilder::parse)
                         .addResultReader(InternalMedianAbsoluteDeviation::new));
         registerAggregation(new AggregationSpec(CardinalityAggregationBuilder.NAME, CardinalityAggregationBuilder::new,
-                CardinalityAggregationBuilder::parse).addResultReader(InternalCardinality::new));
+                CardinalityAggregationBuilder::parse).addResultReader(InternalCardinality::new)
+            .setAggregatorRegistrar(CardinalityAggregationBuilder::registerAggregators));
         registerAggregation(new AggregationSpec(GlobalAggregationBuilder.NAME, GlobalAggregationBuilder::new,
                 GlobalAggregationBuilder::parse).addResultReader(InternalGlobal::new));
         registerAggregation(new AggregationSpec(MissingAggregationBuilder.NAME, MissingAggregationBuilder::new,

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

@@ -35,11 +35,13 @@
 import org.elasticsearch.search.aggregations.support.ValuesSourceAggregationBuilder;
 import org.elasticsearch.search.aggregations.support.ValuesSourceConfig;
 import org.elasticsearch.search.aggregations.support.ValuesSourceParserHelper;
+import org.elasticsearch.search.aggregations.support.ValuesSourceRegistry;
 import org.elasticsearch.search.aggregations.support.ValuesSourceType;
 
 import java.io.IOException;
 import java.util.Map;
 import java.util.Objects;
+import java.util.concurrent.atomic.AtomicBoolean;
 
 public final class CardinalityAggregationBuilder
     extends ValuesSourceAggregationBuilder.LeafOnly<ValuesSource, CardinalityAggregationBuilder> {
@@ -61,6 +63,13 @@ public static AggregationBuilder parse(String aggregationName, XContentParser pa
         return PARSER.parse(parser, new CardinalityAggregationBuilder(aggregationName), null);
     }
 
+    private static AtomicBoolean wasRegistered = new AtomicBoolean(false);
+    public static void registerAggregators(ValuesSourceRegistry valuesSourceRegistry) {
+        if (wasRegistered.compareAndSet(false, true) == true) {
+            CardinalityAggregatorFactory.registerAggregators(valuesSourceRegistry);
+        }
+    }
+
     private Long precisionThreshold = null;
 
     public CardinalityAggregationBuilder(String name) {

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

@@ -20,13 +20,16 @@
 package org.elasticsearch.search.aggregations.metrics;
 
 import org.elasticsearch.index.query.QueryShardContext;
+import org.elasticsearch.search.aggregations.AggregationExecutionException;
 import org.elasticsearch.search.aggregations.Aggregator;
 import org.elasticsearch.search.aggregations.AggregatorFactories;
 import org.elasticsearch.search.aggregations.AggregatorFactory;
 import org.elasticsearch.search.aggregations.pipeline.PipelineAggregator;
+import org.elasticsearch.search.aggregations.support.AggregatorSupplier;
 import org.elasticsearch.search.aggregations.support.ValuesSource;
 import org.elasticsearch.search.aggregations.support.ValuesSourceAggregatorFactory;
 import org.elasticsearch.search.aggregations.support.ValuesSourceConfig;
+import org.elasticsearch.search.aggregations.support.ValuesSourceRegistry;
 import org.elasticsearch.search.internal.SearchContext;
 
 import java.io.IOException;
@@ -47,6 +50,25 @@ class CardinalityAggregatorFactory extends ValuesSourceAggregatorFactory {
         this.precisionThreshold = precisionThreshold;
     }
 
+    static void registerAggregators(ValuesSourceRegistry valuesSourceRegistry) {
+        valuesSourceRegistry.register(CardinalityAggregationBuilder.NAME, (ignored) -> true, cardinalityAggregatorSupplier());
+    }
+
+    private static CardinalityAggregatorSupplier cardinalityAggregatorSupplier(){
+        return new CardinalityAggregatorSupplier() {
+            @Override
+            public Aggregator build(String name,
+                                    ValuesSource valuesSource,
+                                    int precision,
+                                    SearchContext context,
+                                    Aggregator parent,
+                                    List<PipelineAggregator> pipelineAggregators,
+                                    Map<String, Object> metaData) throws IOException {
+                return new CardinalityAggregator(name, valuesSource, precision, context, parent, pipelineAggregators, metaData);
+            }
+        };
+    }
+
     @Override
     protected Aggregator createUnmapped(SearchContext searchContext,
                                             Aggregator parent,
@@ -62,8 +84,14 @@ protected Aggregator doCreateInternal(ValuesSource valuesSource,
                                             boolean collectsFromSingleBucket,
                                             List<PipelineAggregator> pipelineAggregators,
                                             Map<String, Object> metaData) throws IOException {
-        return new CardinalityAggregator(name, valuesSource, precision(), searchContext, parent, pipelineAggregators,
-                metaData);
+        AggregatorSupplier aggregatorSupplier = ValuesSourceRegistry.getInstance().getAggregator(config.valueSourceType(),
+            CardinalityAggregationBuilder.NAME);
+        if (aggregatorSupplier instanceof CardinalityAggregatorSupplier == false) {
+            throw new AggregationExecutionException("Registry miss-match - expected CardinalityAggregatorSupplier, found [" +
+                aggregatorSupplier.getClass().toString() + "]");
+        }
+        CardinalityAggregatorSupplier cardinalityAggregatorSupplier = (CardinalityAggregatorSupplier) aggregatorSupplier;
+        return cardinalityAggregatorSupplier.build(name, valuesSource, precision(), searchContext, parent, pipelineAggregators, metaData);
     }
 
     private int precision() {

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

@@ -0,0 +1,41 @@
+/*
+ * Licensed to Elasticsearch under one or more contributor
+ * license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright
+ * ownership. Elasticsearch 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 org.elasticsearch.search.aggregations.metrics;
+
+import org.elasticsearch.search.aggregations.Aggregator;
+import org.elasticsearch.search.aggregations.pipeline.PipelineAggregator;
+import org.elasticsearch.search.aggregations.support.AggregatorSupplier;
+import org.elasticsearch.search.aggregations.support.ValuesSource;
+import org.elasticsearch.search.internal.SearchContext;
+
+import java.io.IOException;
+import java.util.List;
+import java.util.Map;
+
+public interface CardinalityAggregatorSupplier extends AggregatorSupplier {
+    Aggregator build(String name,
+                     ValuesSource valuesSource,
+                     int precision,
+                     SearchContext context,
+                     Aggregator parent,
+                     List<PipelineAggregator> pipelineAggregators,
+                     Map<String, Object> metaData) throws IOException;
+
+}