Add a unit test for MultiTermsAggregator.buildEmptyAggregations (open…

…search-project#7089)

Signed-off-by: Austin Lee <[email protected]>

server/src/test/java/org/opensearch/search/aggregations/bucket/terms/MultiTermsAggregatorTests.java

@@ -28,36 +28,51 @@
 import org.opensearch.common.network.InetAddresses;
 import org.opensearch.common.settings.Settings;
 import org.opensearch.common.time.DateFormatter;
+import org.opensearch.common.util.BigArrays;
+import org.opensearch.common.util.MockPageCacheRecycler;
+import org.opensearch.index.IndexService;
+import org.opensearch.index.cache.IndexCache;
 import org.opensearch.index.mapper.BooleanFieldMapper;
 import org.opensearch.index.mapper.DateFieldMapper;
 import org.opensearch.index.mapper.GeoPointFieldMapper;
 import org.opensearch.index.mapper.IpFieldMapper;
 import org.opensearch.index.mapper.KeywordFieldMapper;
 import org.opensearch.index.mapper.MappedFieldType;
 import org.opensearch.index.mapper.NumberFieldMapper;
+import org.opensearch.index.query.QueryShardContext;
+import org.opensearch.index.shard.IndexShard;
+import org.opensearch.indices.breaker.NoneCircuitBreakerService;
 import org.opensearch.script.MockScriptEngine;
 import org.opensearch.script.Script;
 import org.opensearch.script.ScriptEngine;
 import org.opensearch.script.ScriptModule;
 import org.opensearch.script.ScriptService;
 import org.opensearch.script.ScriptType;
+import org.opensearch.search.DocValueFormat;
 import org.opensearch.search.aggregations.AggregationBuilder;
+import org.opensearch.search.aggregations.Aggregator;
+import org.opensearch.search.aggregations.AggregatorFactories;
 import org.opensearch.search.aggregations.AggregatorTestCase;
 import org.opensearch.search.aggregations.BucketOrder;
+import org.opensearch.search.aggregations.CardinalityUpperBound;
+import org.opensearch.search.aggregations.InternalAggregation;
 import org.opensearch.search.aggregations.metrics.InternalMax;
 import org.opensearch.search.aggregations.metrics.MaxAggregationBuilder;
 import org.opensearch.search.aggregations.support.CoreValuesSourceType;
 import org.opensearch.search.aggregations.support.MultiTermsValuesSourceConfig;
 import org.opensearch.search.aggregations.support.ValueType;
 import org.opensearch.search.aggregations.support.ValuesSourceType;
+import org.opensearch.search.internal.SearchContext;
 import org.opensearch.search.lookup.LeafDocLookup;
+import org.opensearch.test.TestSearchContext;
 
 import java.io.IOException;
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
+import java.util.UUID;
 import java.util.function.Consumer;
 import java.util.function.Function;
 
@@ -68,8 +83,12 @@
 import static java.util.stream.Collectors.toList;
 import static org.hamcrest.Matchers.closeTo;
 import static org.hamcrest.Matchers.contains;
+import static org.hamcrest.Matchers.empty;
 import static org.hamcrest.Matchers.equalTo;
 import static org.hamcrest.Matchers.hasSize;
+import static org.hamcrest.Matchers.instanceOf;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.when;
 
 public class MultiTermsAggregatorTests extends AggregatorTestCase {
     private static final String FIELD_NAME = "field";
@@ -852,6 +871,56 @@ public void testIncludeExclude() throws IOException {
         );
     }
 
+    public void testEmptyAggregations() throws IOException {
+        QueryShardContext queryShardContext = mock(QueryShardContext.class);
+        IndexShard indexShard = mock(IndexShard.class);
+        BigArrays bigArrays = new BigArrays(new MockPageCacheRecycler(Settings.EMPTY), new NoneCircuitBreakerService(), "");
+        IndexService indexService = mock(IndexService.class);
+        when(indexService.getShardOrNull(0)).thenReturn(indexShard);
+        IndexCache cache = mock(IndexCache.class);
+        when(cache.bitsetFilterCache()).thenReturn(null);
+        when(indexService.cache()).thenReturn(cache);
+        SearchContext context = new TestSearchContext(bigArrays, indexService);
+        when(indexService.newQueryShardContext(0, null, () -> 0L, null)).thenReturn(queryShardContext);
+        AggregatorFactories factories = AggregatorFactories.EMPTY;
+        boolean showTermDocCountError = true;
+        MultiTermsAggregator.InternalValuesSource internalValuesSources = mock(MultiTermsAggregator.InternalValuesSource.class);
+        DocValueFormat format = mock(DocValueFormat.class);
+        BucketOrder order = mock(BucketOrder.class);
+        Aggregator.SubAggCollectionMode collectMode = Aggregator.SubAggCollectionMode.BREADTH_FIRST;
+        TermsAggregator.BucketCountThresholds bucketCountThresholds = mock(TermsAggregator.BucketCountThresholds.class);
+        Aggregator parent = mock(Aggregator.class);
+        CardinalityUpperBound cardinality = CardinalityUpperBound.ONE;
+        Map<String, Object> metadata = new HashMap<>();
+        String k1 = UUID.randomUUID().toString();
+        String v1 = UUID.randomUUID().toString();
+        metadata.put(k1, v1);
+
+        MultiTermsAggregator mAgg = new MultiTermsAggregator(
+            AGG_NAME,
+            factories,
+            showTermDocCountError,
+            List.of(internalValuesSources),
+            List.of(format),
+            order,
+            collectMode,
+            bucketCountThresholds,
+            context,
+            parent,
+            cardinality,
+            metadata
+        );
+        InternalAggregation emptyAgg = mAgg.buildEmptyAggregation();
+
+        MatcherAssert.assertThat(emptyAgg.getName(), equalTo(AGG_NAME));
+        MatcherAssert.assertThat(emptyAgg, instanceOf(InternalMultiTerms.class));
+
+        InternalMultiTerms mt = (InternalMultiTerms) emptyAgg;
+        MatcherAssert.assertThat(mt.getMetadata().keySet(), contains(k1));
+        MatcherAssert.assertThat(mt.getMetadata().get(k1), equalTo(v1));
+        MatcherAssert.assertThat(mt.getBuckets(), empty());
+    }
+
     private void testAggregation(
         Query query,
         List<MultiTermsValuesSourceConfig> terms,