sort missing (null) field values

* since we no longer force fill empty fields, we must handle
  the case where some fields in some hits are missing, and
  sort in a predictable manner.

1 files changed, 6 insertions, 5 deletions

diff --git a/container-search/src/main/java/com/yahoo/search/result/FieldComparator.java b/container-search/src/main/java/com/yahoo/search/result/FieldComparator.java
index 21650d531be..e64e0bc8f8d 100644
--- a/container-search/src/main/java/com/yahoo/search/result/FieldComparator.java
+++ b/container-search/src/main/java/com/yahoo/search/result/FieldComparator.java
@@ -57,11 +57,6 @@ public class FieldComparator extends ChainableComparator {
             Object a = getField(first,fieldName);
             Object b = getField(second,fieldName);
 
-            // If either of the values are null, don't touch the ordering
-            // This is to avoid problems if the sorting is called before the
-            // result is filled.
-            if ((a == null) || (b == null)) return 0;
-
             int x = compareValues(a, b, fieldOrder.getSorter());
             if (x != 0) {
                 if (fieldOrder.getSortOrder() == Sorting.Order.DESCENDING)
@@ -81,6 +76,12 @@ public class FieldComparator extends ChainableComparator {
 
     @SuppressWarnings("rawtypes")
     private int compareValues(Object first, Object second, Sorting.AttributeSorter s) {
+        if (first == null) {
+            if (second == null) return 0;
+            return -1;
+        } else if (second == null) {
+            return 1;
+        }
         if (first.getClass().isInstance(second)
                 && first instanceof Comparable) {
             // We now know: