add check that no aggs add empty buckets in their non final reduce phase

Author: javanna

test/framework/src/main/java/org/elasticsearch/test/InternalAggregationTestCase.java

@@ -119,19 +119,19 @@
 import org.elasticsearch.search.aggregations.metrics.SumAggregationBuilder;
 import org.elasticsearch.search.aggregations.metrics.TopHitsAggregationBuilder;
 import org.elasticsearch.search.aggregations.metrics.ValueCountAggregationBuilder;
-import org.elasticsearch.search.aggregations.pipeline.InternalSimpleValue;
-import org.elasticsearch.search.aggregations.pipeline.ParsedSimpleValue;
-import org.elasticsearch.search.aggregations.pipeline.PipelineAggregator;
+import org.elasticsearch.search.aggregations.pipeline.DerivativePipelineAggregationBuilder;
+import org.elasticsearch.search.aggregations.pipeline.ExtendedStatsBucketPipelineAggregationBuilder;
 import org.elasticsearch.search.aggregations.pipeline.InternalBucketMetricValue;
+import org.elasticsearch.search.aggregations.pipeline.InternalSimpleValue;
 import org.elasticsearch.search.aggregations.pipeline.ParsedBucketMetricValue;
+import org.elasticsearch.search.aggregations.pipeline.ParsedDerivative;
+import org.elasticsearch.search.aggregations.pipeline.ParsedExtendedStatsBucket;
 import org.elasticsearch.search.aggregations.pipeline.ParsedPercentilesBucket;
-import org.elasticsearch.search.aggregations.pipeline.PercentilesBucketPipelineAggregationBuilder;
+import org.elasticsearch.search.aggregations.pipeline.ParsedSimpleValue;
 import org.elasticsearch.search.aggregations.pipeline.ParsedStatsBucket;
+import org.elasticsearch.search.aggregations.pipeline.PercentilesBucketPipelineAggregationBuilder;
+import org.elasticsearch.search.aggregations.pipeline.PipelineAggregator;
 import org.elasticsearch.search.aggregations.pipeline.StatsBucketPipelineAggregationBuilder;
-import org.elasticsearch.search.aggregations.pipeline.ExtendedStatsBucketPipelineAggregationBuilder;
-import org.elasticsearch.search.aggregations.pipeline.ParsedExtendedStatsBucket;
-import org.elasticsearch.search.aggregations.pipeline.DerivativePipelineAggregationBuilder;
-import org.elasticsearch.search.aggregations.pipeline.ParsedDerivative;
 
 import java.io.IOException;
 import java.util.ArrayList;
@@ -151,6 +151,7 @@
 import static org.elasticsearch.test.XContentTestUtils.insertRandomFields;
 import static org.elasticsearch.test.hamcrest.ElasticsearchAssertions.assertToXContentEquivalent;
 import static org.hamcrest.Matchers.equalTo;
+import static org.hamcrest.Matchers.lessThanOrEqualTo;
 
 public abstract class InternalAggregationTestCase<T extends InternalAggregation> extends AbstractWireSerializingTestCase<T> {
     public static final int DEFAULT_MAX_BUCKETS = 100000;
@@ -267,7 +268,14 @@ public void testReduceRandom() {
                 new InternalAggregation.ReduceContext(bigArrays, mockScriptService, bucketConsumer,false);
             @SuppressWarnings("unchecked")
             T reduced = (T) inputs.get(0).reduce(internalAggregations, context);
-            assertMultiBucketConsumer(reduced, bucketConsumer);
+            int initialBucketCount = 0;
+            for (InternalAggregation internalAggregation : internalAggregations) {
+                initialBucketCount += countInnerBucket(internalAggregation);
+            }
+            int reducedBucketCount = countInnerBucket(reduced);
+            //check that non final reduction never adds buckets
+            assertThat(reducedBucketCount, lessThanOrEqualTo(initialBucketCount));
+            assertMultiBucketConsumer(reducedBucketCount, bucketConsumer);
             toReduce = new ArrayList<>(toReduce.subList(r, toReduceSize));
             toReduce.add(reduced);
         }
@@ -332,14 +340,14 @@ protected NamedXContentRegistry xContentRegistry() {
 
     public final void testFromXContent() throws IOException {
         final T aggregation = createTestInstance();
-        final Aggregation parsedAggregation = parseAndAssert(aggregation, randomBoolean(), false);
-        assertFromXContent(aggregation, (ParsedAggregation) parsedAggregation);
+        final ParsedAggregation parsedAggregation = parseAndAssert(aggregation, randomBoolean(), false);
+        assertFromXContent(aggregation, parsedAggregation);
     }
 
     public final void testFromXContentWithRandomFields() throws IOException {
         final T aggregation = createTestInstance();
-        final Aggregation parsedAggregation = parseAndAssert(aggregation, randomBoolean(), true);
-        assertFromXContent(aggregation, (ParsedAggregation) parsedAggregation);
+        final ParsedAggregation parsedAggregation = parseAndAssert(aggregation, randomBoolean(), true);
+        assertFromXContent(aggregation, parsedAggregation);
     }
 
     protected abstract void assertFromXContent(T aggregation, ParsedAggregation parsedAggregation) throws IOException;
@@ -423,6 +431,10 @@ protected static DocValueFormat randomNumericDocValueFormat() {
     }
 
     public static void assertMultiBucketConsumer(Aggregation agg, MultiBucketConsumer bucketConsumer) {
-        assertThat(bucketConsumer.getCount(), equalTo(countInnerBucket(agg)));
+        assertMultiBucketConsumer(countInnerBucket(agg), bucketConsumer);
+    }
+
+    private static void assertMultiBucketConsumer(int innerBucketCount, MultiBucketConsumer bucketConsumer) {
+        assertThat(bucketConsumer.getCount(), equalTo(innerBucketCount));
     }
 }