Handle null stats case

Author: the-other-tim-brown

xtable-core/src/main/java/org/apache/xtable/delta/DeltaStatsExtractor.java

@@ -21,6 +21,7 @@
 import java.io.IOException;
 import java.util.ArrayDeque;
 import java.util.Arrays;
+import java.util.Collections;
 import java.util.HashMap;
 import java.util.HashSet;
 import java.util.List;
@@ -36,6 +37,8 @@
 import lombok.NoArgsConstructor;
 import lombok.Value;
 
+import org.apache.commons.lang3.StringUtils;
+
 import org.apache.spark.sql.delta.actions.AddFile;
 
 import com.fasterxml.jackson.core.JsonProcessingException;
@@ -173,6 +176,9 @@ private void insertValueAtPath(Map<String, Object> jsonObject, String[] pathPart
   }
 
   public List<ColumnStat> getColumnStatsForFile(AddFile addFile, List<InternalField> fields) {
+    if (StringUtils.isEmpty(addFile.stats())) {
+      return Collections.emptyList();
+    }
     // TODO: Additional work needed to track maps & arrays.
     try {
       DeltaStats deltaStats = MAPPER.readValue(addFile.stats(), DeltaStats.class);

xtable-core/src/test/java/org/apache/xtable/delta/TestDeltaStatsExtractor.java

@@ -23,6 +23,7 @@
 
 import java.io.IOException;
 import java.util.Arrays;
+import java.util.Collections;
 import java.util.HashMap;
 import java.util.HashSet;
 import java.util.List;
@@ -183,6 +184,15 @@ void convertStatsToInternalRepresentation() throws IOException {
     assertEquals(expected, actual);
   }
 
+  @Test
+  void convertNullStatsToInternalRepresentation() {
+    List<InternalField> fields = getSchemaFields();
+    AddFile addFile = new AddFile("file://path/to/file", null, 0, 0, true, null, null, null);
+    DeltaStatsExtractor extractor = DeltaStatsExtractor.getInstance();
+    List<ColumnStat> actual = extractor.getColumnStatsForFile(addFile, fields);
+    assertEquals(Collections.emptyList(), actual);
+  }
+
   private List<InternalField> getSchemaFields() {
     return Arrays.asList(
         InternalField.builder()