SERVER-55480 Fix use-after-move in min max window functions

2 files changed, 19 insertions, 1 deletions

diff --git a/src/mongo/db/pipeline/window_function/window_function_min_max.h b/src/mongo/db/pipeline/window_function/window_function_min_max.h
index 65e64f304cd..e450caa6bc1 100644
--- a/src/mongo/db/pipeline/window_function/window_function_min_max.h
+++ b/src/mongo/db/pipeline/window_function/window_function_min_max.h
@@ -49,8 +49,8 @@ public:
     }
 
     void add(Value value) final {
-        _values.insert(std::move(value));
         _memUsageBytes += value.getApproximateSize();
+        _values.insert(std::move(value));
     }
 
     void remove(Value value) final {
diff --git a/src/mongo/db/pipeline/window_function/window_function_min_max_test.cpp b/src/mongo/db/pipeline/window_function/window_function_min_max_test.cpp
index 62102ef20c0..68a4cabe0de 100644
--- a/src/mongo/db/pipeline/window_function/window_function_min_max_test.cpp
+++ b/src/mongo/db/pipeline/window_function/window_function_min_max_test.cpp
@@ -133,5 +133,23 @@ TEST_F(WindowFunctionMinMaxTest, Ties) {
     ASSERT_VALUE_EQ(max.getValue(), y);
 }
 
+TEST_F(WindowFunctionMinMaxTest, TracksMemoryUsageOnAddAndRemove) {
+    size_t trackingSize = sizeof(WindowFunctionMin);
+    ASSERT_EQ(min.getApproximateSize(), trackingSize);
+
+    auto largeStr = Value{"this is quite a long string"_sd};
+    min.add(largeStr);
+    trackingSize += largeStr.getApproximateSize();
+    ASSERT_EQ(min.getApproximateSize(), trackingSize);
+
+    min.add(largeStr);
+    trackingSize += largeStr.getApproximateSize();
+    ASSERT_EQ(min.getApproximateSize(), trackingSize);
+
+    min.remove(largeStr);
+    trackingSize -= largeStr.getApproximateSize();
+    ASSERT_EQ(min.getApproximateSize(), trackingSize);
+}
+
 }  // namespace
 }  // namespace mongo