Return NaN for non-present fields of FieldStatsResult

Before this change, an ExtendedStatsAggregation could include an
arbitrary number of fields that are null. Assigning them a non-boxed
field type leads to an NPE and a 500 is being returned to the caller
when the result of a extended field stats widget is requested.

This change properly assigns a valid value for those fields, so a result
(albeit possibly containing NaN for one or more fields) is being
returned to the caller.

Fixes #4026

(cherry picked from commit 882727e)

graylog2-server/src/main/java/org/graylog2/indexer/results/FieldStatsResult.java

@@ -44,16 +44,16 @@ public FieldStatsResult(ValueCountAggregation valueCountAggregation,
                             long tookMs) {
         super(query, source, tookMs);
         this.count = getValueCount(valueCountAggregation, extendedStatsAggregation);
-        this.cardinality = cardinalityAggregation == null ? Long.MIN_VALUE : cardinalityAggregation.getCardinality();
+        this.cardinality = cardinalityAggregation == null || cardinalityAggregation.getCardinality() == null ? Long.MIN_VALUE : cardinalityAggregation.getCardinality();
 
         if (extendedStatsAggregation != null) {
-            sum = extendedStatsAggregation.getSum();
-            sumOfSquares = extendedStatsAggregation.getSumOfSquares();
-            mean = extendedStatsAggregation.getAvg();
-            min = extendedStatsAggregation.getMin();
-            max = extendedStatsAggregation.getMax();
-            variance = extendedStatsAggregation.getVariance();
-            stdDeviation = extendedStatsAggregation.getStdDeviation();
+            sum = extendedStatsAggregation.getSum() != null ? extendedStatsAggregation.getSum() : Double.NaN;
+            sumOfSquares = extendedStatsAggregation.getSumOfSquares() != null ? extendedStatsAggregation.getSumOfSquares() : Double.NaN;
+            mean = extendedStatsAggregation.getAvg() != null ? extendedStatsAggregation.getAvg() : Double.NaN;
+            min = extendedStatsAggregation.getMin() != null ? extendedStatsAggregation.getMin() : Double.NaN;
+            max = extendedStatsAggregation.getMax() != null ? extendedStatsAggregation.getMax() : Double.NaN;
+            variance = extendedStatsAggregation.getVariance() != null ? extendedStatsAggregation.getVariance() : Double.NaN;
+            stdDeviation = extendedStatsAggregation.getStdDeviation() != null ? extendedStatsAggregation.getStdDeviation() : Double.NaN;
         } else {
             sum = Double.NaN;
             sumOfSquares = Double.NaN;
@@ -82,9 +82,9 @@ private FieldStatsResult(String query, String bytesReference) {
     }
 
     private long getValueCount(ValueCountAggregation valueCountAggregation, ExtendedStatsAggregation extendedStatsAggregation) {
-        if (valueCountAggregation != null) {
+        if (valueCountAggregation != null && valueCountAggregation.getValueCount() != null) {
             return valueCountAggregation.getValueCount();
-        } else if (extendedStatsAggregation != null) {
+        } else if (extendedStatsAggregation != null && extendedStatsAggregation.getCount() != null) {
             return extendedStatsAggregation.getCount();
         }
         return Long.MIN_VALUE;

graylog2-server/src/test/java/org/graylog2/indexer/results/FieldStatsResultTest.java

@@ -0,0 +1,62 @@
+/**
+ * This file is part of Graylog.
+ *
+ * Graylog is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * Graylog is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with Graylog.  If not, see <http://www.gnu.org/licenses/>.
+ */
+package org.graylog2.indexer.results;
+
+import io.searchbox.core.search.aggregation.ExtendedStatsAggregation;
+import org.junit.Test;
+
+import java.util.Collections;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.when;
+
+public class FieldStatsResultTest {
+    @Test
+    public void worksForNullFieldsInAggregationResults() throws Exception {
+        final ExtendedStatsAggregation extendedStatsAggregation = mock(ExtendedStatsAggregation.class);
+
+        when(extendedStatsAggregation.getCount()).thenReturn(null);
+        when(extendedStatsAggregation.getSum()).thenReturn(null);
+        when(extendedStatsAggregation.getSumOfSquares()).thenReturn(null);
+        when(extendedStatsAggregation.getAvg()).thenReturn(null);
+        when(extendedStatsAggregation.getMin()).thenReturn(null);
+        when(extendedStatsAggregation.getMax()).thenReturn(null);
+        when(extendedStatsAggregation.getVariance()).thenReturn(null);
+        when(extendedStatsAggregation.getStdDeviation()).thenReturn(null);
+
+        final FieldStatsResult result = new FieldStatsResult(null,
+                extendedStatsAggregation,
+                null,
+                Collections.emptyList(),
+                null,
+                null,
+                0);
+
+        assertThat(result).isNotNull();
+        assertThat(result.getSum()).isEqualTo(Double.NaN);
+        assertThat(result.getSumOfSquares()).isEqualTo(Double.NaN);
+        assertThat(result.getMean()).isEqualTo(Double.NaN);
+        assertThat(result.getMin()).isEqualTo(Double.NaN);
+        assertThat(result.getMax()).isEqualTo(Double.NaN);
+        assertThat(result.getVariance()).isEqualTo(Double.NaN);
+        assertThat(result.getStdDeviation()).isEqualTo(Double.NaN);
+
+        assertThat(result.getCount()).isEqualTo(Long.MIN_VALUE);
+        assertThat(result.getCardinality()).isEqualTo(Long.MIN_VALUE);
+    }
+}