Add unit tests for the missing aggregator

core/src/test/java/org/elasticsearch/search/aggregations/AggregatorTestCase.java

@@ -238,13 +238,16 @@ protected <A extends InternalAggregation, C extends Aggregator> A searchAndReduc
             if (aggs.isEmpty()) {
                 return null;
             } else {
-                if (randomBoolean()) {
+                if (randomBoolean() && aggs.size() > 1) {
                     // sometimes do an incremental reduce
-                    List<InternalAggregation> internalAggregations = randomSubsetOf(randomIntBetween(1, aggs.size()), aggs);
-                    A internalAgg = (A) aggs.get(0).doReduce(internalAggregations,
+                    int toReduceSize = aggs.size();
+                    Collections.shuffle(aggs, random());
+                    int r = randomIntBetween(1, toReduceSize);
+                    List<InternalAggregation> toReduce = aggs.subList(0, r);
+                    A reduced = (A) aggs.get(0).doReduce(toReduce,
                         new InternalAggregation.ReduceContext(root.context().bigArrays(), null, false));
-                    aggs.removeAll(internalAggregations);
-                    aggs.add(internalAgg);
+                    aggs = aggs.subList(r, toReduceSize);
+                    aggs.add(reduced);
                 }
                 // now do the final reduce
                 @SuppressWarnings("unchecked")

core/src/test/java/org/elasticsearch/search/aggregations/InternalAggregationTestCase.java

@@ -63,9 +63,9 @@ public void testReduceRandom() {
         ScriptService mockScriptService = mockScriptService();
         MockBigArrays bigArrays = new MockBigArrays(Settings.EMPTY, new NoneCircuitBreakerService());
         if (randomBoolean() && toReduce.size() > 1) {
+            // sometimes do an incremental reduce
             Collections.shuffle(toReduce, random());
-            // we leave at least one element in the list
-            int r = Math.max(1, randomIntBetween(0, toReduceSize - 2));
+            int r = randomIntBetween(1, toReduceSize);
             List<InternalAggregation> internalAggregations = toReduce.subList(0, r);
             InternalAggregation.ReduceContext context =
                 new InternalAggregation.ReduceContext(bigArrays, mockScriptService, false);

core/src/test/java/org/elasticsearch/search/aggregations/bucket/missing/MissingAggregatorTests.java

@@ -0,0 +1,124 @@
+/*
+ * 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.bucket.missing;
+
+import org.apache.lucene.document.Document;
+import org.apache.lucene.document.SortedNumericDocValuesField;
+import org.apache.lucene.index.DirectoryReader;
+import org.apache.lucene.index.IndexReader;
+import org.apache.lucene.index.RandomIndexWriter;
+import org.apache.lucene.search.IndexSearcher;
+import org.apache.lucene.search.Query;
+import org.apache.lucene.store.Directory;
+import org.elasticsearch.common.lucene.search.Queries;
+import org.elasticsearch.index.mapper.MappedFieldType;
+import org.elasticsearch.index.mapper.NumberFieldMapper;
+import org.elasticsearch.search.aggregations.AggregatorTestCase;
+import org.elasticsearch.search.aggregations.support.ValueType;
+
+import java.io.IOException;
+import java.util.concurrent.atomic.AtomicInteger;
+import java.util.function.Consumer;
+
+
+public class MissingAggregatorTests extends AggregatorTestCase {
+    public void testMatchNoDocs() throws IOException {
+        int numDocs = randomIntBetween(10, 200);
+        testBothCases(numDocs, Queries.newMatchAllQuery(),
+            doc -> doc.add(new SortedNumericDocValuesField("field", randomLong())),
+            internalMissing -> assertEquals(internalMissing.getDocCount(), 0));
+    }
+
+    public void testMatchAllDocs() throws IOException {
+        int numDocs = randomIntBetween(10, 200);
+        testBothCases(numDocs, Queries.newMatchAllQuery(),
+            doc -> doc.add(new SortedNumericDocValuesField("another_field", randomLong())),
+            internalMissing -> assertEquals(internalMissing.getDocCount(), numDocs));
+    }
+
+    public void testMatchSparse() throws IOException {
+        int numDocs = randomIntBetween(100, 200);
+        final AtomicInteger count = new AtomicInteger();
+        testBothCases(numDocs, Queries.newMatchAllQuery(),
+            doc -> {
+                if (randomBoolean()) {
+                    doc.add(new SortedNumericDocValuesField("another_field", randomLong()));
+                    count.incrementAndGet();
+                } else {
+                    doc.add(new SortedNumericDocValuesField("field", randomLong()));
+                }
+            },
+            internalMissing -> {
+                assertEquals(internalMissing.getDocCount(), count.get());
+                count.set(0);
+            });
+    }
+
+    private void testBothCases(int numDocs,
+                               Query query,
+                               Consumer<Document> consumer,
+                               Consumer<InternalMissing> verify) throws IOException {
+        executeTestCase(numDocs, query, consumer, verify, false);
+        executeTestCase(numDocs, query, consumer, verify, true);
+
+    }
+
+    private void executeTestCase(int numDocs,
+                                 Query query,
+                                 Consumer<Document> consumer,
+                                 Consumer<InternalMissing> verify,
+                                 boolean reduced) throws IOException {
+        try (Directory directory = newDirectory()) {
+            try (RandomIndexWriter indexWriter = new RandomIndexWriter(random(), directory)) {
+                Document document = new Document();
+                for (int i = 0; i < numDocs; i++) {
+                    if (frequently()) {
+                        indexWriter.commit();
+                    }
+                    consumer.accept(document);
+                    indexWriter.addDocument(document);
+                    document.clear();
+                }
+            }
+
+            try (IndexReader indexReader = DirectoryReader.open(directory)) {
+                IndexSearcher indexSearcher =
+                    newSearcher(indexReader, true, true);
+                MissingAggregationBuilder builder =
+                    new MissingAggregationBuilder("_name", ValueType.LONG);
+                builder.field("field");
+
+                NumberFieldMapper.Builder mapperBuilder = new NumberFieldMapper.Builder("_name",
+                    NumberFieldMapper.NumberType.LONG);
+                MappedFieldType fieldType = mapperBuilder.fieldType();
+                fieldType.setHasDocValues(true);
+                fieldType.setName(builder.field());
+
+                InternalMissing missing;
+                if (reduced) {
+                    missing = searchAndReduce(indexSearcher, query, builder, fieldType);
+                } else {
+                    missing = search(indexSearcher, query, builder, fieldType);
+                }
+                verify.accept(missing);
+            }
+        }
+    }
+}