Fixes a bug in empty collections. Contributed by Venkatesh Seetharam

repository/src/main/java/org/apache/hadoop/metadata/repository/graph/GraphBackedMetadataRepository.java

@@ -463,7 +463,7 @@ public class GraphBackedMetadataRepository implements MetadataRepository {
             LOG.debug("Mapping instance {} to vertex {} for name {}",
                     typedInstance.getTypeName(), instanceVertex, attributeInfo.name);
             List list = (List) typedInstance.get(attributeInfo.name);
-            if (list == null) {
+            if (list == null || list.isEmpty()) {
                 return;
             }
 
@@ -495,7 +495,7 @@ public class GraphBackedMetadataRepository implements MetadataRepository {
                     typedInstance.getTypeName(), instanceVertex, attributeInfo.name);
             @SuppressWarnings("unchecked")
             Map<Object, Object> collection = (Map<Object, Object>) typedInstance.get(attributeInfo.name);
-            if (collection == null) {
+            if (collection == null || collection.isEmpty()) {
                 return;
             }
 

repository/src/test/java/org/apache/hadoop/metadata/services/GraphBackedMetadataRepositoryTest.java → repository/src/test/java/org/apache/hadoop/metadata/repository/graph/GraphBackedMetadataRepositoryTest.java

@@ -16,7 +16,7 @@
  * limitations under the License.
  */
 
-package org.apache.hadoop.metadata.services;
+package org.apache.hadoop.metadata.repository.graph;
 
 import com.google.common.collect.ImmutableList;
 import com.thinkaurelius.titan.core.TitanGraph;
@@ -27,9 +27,6 @@ import org.apache.hadoop.metadata.ITypedReferenceableInstance;
 import org.apache.hadoop.metadata.MetadataException;
 import org.apache.hadoop.metadata.Referenceable;
 import org.apache.hadoop.metadata.RepositoryMetadataModule;
-import org.apache.hadoop.metadata.repository.graph.GraphBackedMetadataRepository;
-import org.apache.hadoop.metadata.repository.graph.GraphHelper;
-import org.apache.hadoop.metadata.repository.graph.TitanGraphService;
 import org.apache.hadoop.metadata.types.AttributeDefinition;
 import org.apache.hadoop.metadata.types.ClassType;
 import org.apache.hadoop.metadata.types.DataTypes;