fix issue #2744. Check for null before combining metrics (#2774)

processing/src/main/java/io/druid/segment/IndexMerger.java

@@ -1474,7 +1474,15 @@ public class IndexMerger
       Object[] rhsMetrics = rhs.getMetrics();
 
       for (int i = 0; i < metrics.length; ++i) {
-        metrics[i] = metricAggs[i].combine(lhsMetrics[i], rhsMetrics[i]);
+        Object lhsMetric = lhsMetrics[i];
+        Object rhsMetric = rhsMetrics[i];
+        if (lhsMetric == null) {
+          metrics[i] = rhsMetric;
+        } else if (rhsMetric == null) {
+          metrics[i] = lhsMetric;
+        } else {
+          metrics[i] = metricAggs[i].combine(lhsMetric, rhsMetric);
+        }
       }
 
       final Rowboat retVal = new Rowboat(

processing/src/test/java/io/druid/segment/IndexMergerTest.java

@@ -875,7 +875,11 @@ public class IndexMergerTest
   public void testMergeWithDimensionsList() throws Exception
   {
     IncrementalIndexSchema schema = new IncrementalIndexSchema.Builder()
-        .withDimensionsSpec(new DimensionsSpec(DimensionsSpec.getDefaultSchemas(Arrays.asList("dimA", "dimB", "dimC")), null, null))
+        .withDimensionsSpec(new DimensionsSpec(
+            DimensionsSpec.getDefaultSchemas(Arrays.asList("dimA", "dimB", "dimC")),
+            null,
+            null
+        ))
         .withMinTimestamp(0L)
         .withQueryGranularity(QueryGranularity.NONE)
         .withMetrics(new AggregatorFactory[]{new CountAggregatorFactory("count")})
@@ -1418,19 +1422,28 @@ public class IndexMergerTest
 
   }
 
+  @Test
   public void testMismatchedDimensions() throws IOException, IndexSizeExceededException
   {
     IncrementalIndex index1 = IncrementalIndexTest.createIndex(new AggregatorFactory[]{
         new LongSumAggregatorFactory("A", "A")
     });
-    index1.add(new MapBasedInputRow(1L, Lists.newArrayList("d1", "d2"), ImmutableMap.<String, Object>of("d1", "a", "d2", "z", "A", 1)));
+    index1.add(new MapBasedInputRow(
+        1L,
+        Lists.newArrayList("d1", "d2"),
+        ImmutableMap.<String, Object>of("d1", "a", "d2", "z", "A", 1)
+    ));
     closer.closeLater(index1);
 
     IncrementalIndex index2 = IncrementalIndexTest.createIndex(new AggregatorFactory[]{
         new LongSumAggregatorFactory("A", "A"),
         new LongSumAggregatorFactory("C", "C")
     });
-    index2.add(new MapBasedInputRow(1L, Lists.newArrayList("d2"), ImmutableMap.<String, Object>of("d2", "z", "A", 2, "C", 100)));
+    index2.add(new MapBasedInputRow(
+        1L,
+        Lists.newArrayList("d1", "d2"),
+        ImmutableMap.<String, Object>of("d1", "a", "d2", "z", "A", 2, "C", 100)
+    ));
     closer.closeLater(index2);
 
     Interval interval = new Interval(0, new DateTime().getMillis());
@@ -1453,6 +1466,131 @@ public class IndexMergerTest
     );
   }
 
+  @Test
+  public void testAddMetrics() throws IOException
+  {
+    IncrementalIndex index1 = IncrementalIndexTest.createIndex(new AggregatorFactory[]{
+        new LongSumAggregatorFactory("A", "A")
+    });
+    closer.closeLater(index1);
+    long timestamp = System.currentTimeMillis();
+    index1.add(
+        new MapBasedInputRow(
+            timestamp,
+            Arrays.asList("dim1", "dim2"),
+            ImmutableMap.<String, Object>of("dim1", "1", "dim2", "2", "A", 5)
+        )
+    );
+
+    IncrementalIndex index2 = IncrementalIndexTest.createIndex(new AggregatorFactory[]{
+        new LongSumAggregatorFactory("A", "A"),
+        new LongSumAggregatorFactory("C", "C")
+    });
+
+    index2.add(
+        new MapBasedInputRow(
+            timestamp,
+            Arrays.asList("dim1", "dim2"),
+            ImmutableMap.<String, Object>of("dim1", "1", "dim2", "2", "A", 5, "C", 6)
+        )
+    );
+    closer.closeLater(index2);
+
+    Interval interval = new Interval(0, new DateTime().getMillis());
+    RoaringBitmapFactory factory = new RoaringBitmapFactory();
+    ArrayList<IndexableAdapter> toMerge = Lists.<IndexableAdapter>newArrayList(
+        new IncrementalIndexAdapter(interval, index1, factory),
+        new IncrementalIndexAdapter(interval, index2, factory)
+
+    );
+
+    final File tmpDirMerged = temporaryFolder.newFolder();
+
+    File merged = INDEX_MERGER.merge(
+        toMerge,
+        new AggregatorFactory[]{
+            new LongSumAggregatorFactory("A", "A"),
+            new LongSumAggregatorFactory("C", "C")
+        },
+        tmpDirMerged,
+        indexSpec
+    );
+    final QueryableIndexStorageAdapter adapter = new QueryableIndexStorageAdapter(closer.closeLater(INDEX_IO.loadIndex(
+        merged)));
+    Assert.assertEquals(ImmutableSet.of("A", "C"), ImmutableSet.copyOf(adapter.getAvailableMetrics()));
+
+  }
+
+  @Test
+  public void testAddMetricsBothSidesNull() throws IOException
+  {
+    IncrementalIndex index1 = IncrementalIndexTest.createIndex(new AggregatorFactory[]{
+        new LongSumAggregatorFactory("A", "A")
+    });
+    closer.closeLater(index1);
+    long timestamp = System.currentTimeMillis();
+    index1.add(
+        new MapBasedInputRow(
+            timestamp,
+            Arrays.asList("dim1", "dim2"),
+            ImmutableMap.<String, Object>of("dim1", "1", "dim2", "2", "A", 5)
+        )
+    );
+
+    IncrementalIndex index2 = IncrementalIndexTest.createIndex(new AggregatorFactory[]{
+        new LongSumAggregatorFactory("A", "A"),
+        new LongSumAggregatorFactory("C", "C")
+    });
+
+    index2.add(
+        new MapBasedInputRow(
+            timestamp,
+            Arrays.asList("dim1", "dim2"),
+            ImmutableMap.<String, Object>of("dim1", "1", "dim2", "2", "A", 5, "C", 6)
+        )
+    );
+    closer.closeLater(index2);
+
+
+    IncrementalIndex index3 = IncrementalIndexTest.createIndex(new AggregatorFactory[]{
+        new LongSumAggregatorFactory("A", "A")
+    });
+
+    index3.add(
+        new MapBasedInputRow(
+            timestamp,
+            Arrays.asList("dim1", "dim2"),
+            ImmutableMap.<String, Object>of("dim1", "1", "dim2", "2", "A", 5)
+        )
+    );
+
+
+    Interval interval = new Interval(0, new DateTime().getMillis());
+    RoaringBitmapFactory factory = new RoaringBitmapFactory();
+    ArrayList<IndexableAdapter> toMerge = Lists.<IndexableAdapter>newArrayList(
+        new IncrementalIndexAdapter(interval, index1, factory),
+        new IncrementalIndexAdapter(interval, index2, factory),
+        new IncrementalIndexAdapter(interval, index3, factory)
+
+    );
+
+    final File tmpDirMerged = temporaryFolder.newFolder();
+
+    File merged = INDEX_MERGER.merge(
+        toMerge,
+        new AggregatorFactory[]{
+            new LongSumAggregatorFactory("A", "A"),
+            new LongSumAggregatorFactory("C", "C")
+        },
+        tmpDirMerged,
+        indexSpec
+    );
+    final QueryableIndexStorageAdapter adapter = new QueryableIndexStorageAdapter(closer.closeLater(INDEX_IO.loadIndex(
+        merged)));
+    Assert.assertEquals(ImmutableSet.of("A", "C"), ImmutableSet.copyOf(adapter.getAvailableMetrics()));
+
+  }
+
   @Test
   public void testMismatchedMetrics() throws IOException
   {
@@ -1511,7 +1649,8 @@ public class IndexMergerTest
     );
 
     // Since D was not present in any of the indices, it is not present in the output
-    final QueryableIndexStorageAdapter adapter = new QueryableIndexStorageAdapter(closer.closeLater(INDEX_IO.loadIndex(merged)));
+    final QueryableIndexStorageAdapter adapter = new QueryableIndexStorageAdapter(closer.closeLater(INDEX_IO.loadIndex(
+        merged)));
     Assert.assertEquals(ImmutableSet.of("A", "B", "C"), ImmutableSet.copyOf(adapter.getAvailableMetrics()));
 
   }
@@ -1551,7 +1690,8 @@ public class IndexMergerTest
         tmpDirMerged,
         indexSpec
     );
-    final QueryableIndexStorageAdapter adapter = new QueryableIndexStorageAdapter(closer.closeLater(INDEX_IO.loadIndex(merged)));
+    final QueryableIndexStorageAdapter adapter = new QueryableIndexStorageAdapter(closer.closeLater(INDEX_IO.loadIndex(
+        merged)));
     Assert.assertEquals(ImmutableSet.of("A", "B", "C"), ImmutableSet.copyOf(adapter.getAvailableMetrics()));
   }