Merge c205372 into d45e1d5

bwaldvogel · Nov 2, 2020 · 0b5e90d · 0b5e90d
2 parents d45e1d5 + c205372
commit 0b5e90d
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Showing 3 changed files with 38 additions and 2 deletions.
diff --git a/core/src/main/java/de/bwaldvogel/mongo/backend/aggregation/accumulator/FirstAccumulator.java b/core/src/main/java/de/bwaldvogel/mongo/backend/aggregation/accumulator/FirstAccumulator.java
@@ -13,8 +13,12 @@ public FirstAccumulator(String field, Object expression) {
 
     @Override
     public void aggregate(Object value) {
-        if (first && !(value instanceof Missing)) {
-            firstValue = value;
+        if (first) {
+            if (!(value instanceof Missing)) {
+                firstValue = value;
+            } else {
+                firstValue = null;
+            }
             first = false;
         }
     }

diff --git a/core/src/main/java/de/bwaldvogel/mongo/backend/aggregation/accumulator/LastAccumulator.java b/core/src/main/java/de/bwaldvogel/mongo/backend/aggregation/accumulator/LastAccumulator.java
@@ -14,6 +14,8 @@ public LastAccumulator(String field, Object expression) {
     public void aggregate(Object value) {
         if (!(value instanceof Missing)) {
             lastValue = value;
+        } else {
+            lastValue = null;
         }
     }
 

diff --git a/test-common/src/main/java/de/bwaldvogel/mongo/backend/AbstractAggregationTest.java b/test-common/src/main/java/de/bwaldvogel/mongo/backend/AbstractAggregationTest.java
@@ -930,6 +930,36 @@ void testAggregateWithFirstAndLast_Missing() throws Exception {
             );
     }
 
+    @Test
+    void testAggregateWithGroupingAndFirstMissing() throws Exception {
+        Document sort = json("$sort: {index: 1}");
+        Document group = json("$group: {_id: '$index', first: { $first: '$field1' }}");
+        List<Document> pipeline = Arrays.asList(sort, group);
+
+        collection.insertOne(json("_id: 1, index: 1"));
+        collection.insertOne(json("_id: 2, index: 1, field1: 'abc'"));
+
+        assertThat(collection.aggregate(pipeline))
+                .containsExactly(
+                        json("_id: 1, first: null")
+                );
+    }
+
+    @Test
+    void testAggregateWithGroupingAndLastMissing() throws Exception {
+        Document sort = json("$sort: {index: 1}");
+        Document group = json("$group: {_id: '$index', last: { $last: '$field1' }}");
+        List<Document> pipeline = Arrays.asList(sort, group);
+
+        collection.insertOne(json("_id: 1, index: 1, field1: 'abc'"));
+        collection.insertOne(json("_id: 2, index: 1"));
+
+        assertThat(collection.aggregate(pipeline))
+                .containsExactly(
+                        json("_id: 1, last: null")
+                );
+    }
+
     @Test
     void testAggregateWithPush() throws Exception {
         List<Document> pipeline = jsonList("$group: {_id: null, a: {$push: '$a'}, b: {$push: {v: '$b'}}, c: {$push: '$c'}}");