SERVER-44065 Call optimize() on ParsedAggregationProjection when building projection executor from AST

2 files changed, 8 insertions, 0 deletions

diff --git a/src/mongo/db/exec/projection_executor.cpp b/src/mongo/db/exec/projection_executor.cpp
index 29192f19547..19a7fd7eb55 100644
--- a/src/mongo/db/exec/projection_executor.cpp
+++ b/src/mongo/db/exec/projection_executor.cpp
@@ -252,6 +252,7 @@ auto buildProjectionExecutor(boost::intrusive_ptr<ExpressionContext> expCtx,
     ProjectionExecutorVisitor<Executor> executorVisitor{&context};
     projection_ast::PathTrackingWalker walker{&context, {&executorVisitor}, {}};
     projection_ast_walker::walk(&walker, root);
+    context.data().executor->optimize();
     return std::move(context.data().executor);
 }
 }  // namespace
diff --git a/src/mongo/db/exec/projection_executor_test.cpp b/src/mongo/db/exec/projection_executor_test.cpp
index 7d3b7410205..a1ac7467510 100644
--- a/src/mongo/db/exec/projection_executor_test.cpp
+++ b/src/mongo/db/exec/projection_executor_test.cpp
@@ -176,4 +176,11 @@ TEST_F(ProjectionExecutorTest, CanProjectFindSliceAndPositional) {
         Document{fromjson("{a: {b: [2,3]}, c: [6]}")},
         executor->applyTransformation(Document{fromjson("{a: {b: [1,2,3,4]}, c: [5,6,7]}")}));
 }
+
+TEST_F(ProjectionExecutorTest, ExecutorOptimizesExpression) {
+    auto proj = parseWithDefaultPolicies(fromjson("{a: 1, b: {$add: [1, 2]}}"));
+    auto executor = buildProjectionExecutor(getExpCtx(), &proj, {});
+    ASSERT_DOCUMENT_EQ(Document{fromjson("{_id: true, a: true, b: {$const: 3}}")},
+                       executor->serializeTransformation(boost::none));
+}
 }  // namespace mongo::projection_executor