SERVER-27115 Allow $type on a renamed field to swap before the rename.

3 files changed, 15 insertions, 9 deletions

diff --git a/src/mongo/db/matcher/expression_algo.cpp b/src/mongo/db/matcher/expression_algo.cpp
index 693ef9f55e9..a648d1a4b28 100644
--- a/src/mongo/db/matcher/expression_algo.cpp
+++ b/src/mongo/db/matcher/expression_algo.cpp
@@ -275,7 +275,7 @@ unique_ptr<MatchExpression> createNorOfNodes(std::vector<unique_ptr<MatchExpress
 }
 
 void applyRenamesToExpression(MatchExpression* expr, const StringMap<std::string>& renames) {
-    if (expr->isArray() || expr->matchType() == MatchExpression::TYPE_OPERATOR) {
+    if (expr->isArray()) {
         return;
     }
 
@@ -419,8 +419,8 @@ bool isIndependentOf(const MatchExpression& expr, const std::set<std::string>& p
         return true;
     }
 
-    // Certain kinds of match expressions are never considered independent.
-    if (expr.isArray() || expr.matchType() == MatchExpression::TYPE_OPERATOR) {
+    // Array match expressions are never considered independent.
+    if (expr.isArray()) {
         return false;
     }
 
diff --git a/src/mongo/db/matcher/expression_algo_test.cpp b/src/mongo/db/matcher/expression_algo_test.cpp
index 14678945b4f..e02e41c27cc 100644
--- a/src/mongo/db/matcher/expression_algo_test.cpp
+++ b/src/mongo/db/matcher/expression_algo_test.cpp
@@ -1064,7 +1064,7 @@ TEST(SplitMatchExpression, ShouldNotMoveElemMatchValueAcrossRename) {
     ASSERT_BSONOBJ_EQ(secondBob.obj(), fromjson("{a: {$elemMatch: {$eq: 3}}}"));
 }
 
-TEST(SplitMatchExpression, ShouldNotMoveTypeAcrossRename) {
+TEST(SplitMatchExpression, ShouldMoveTypeAcrossRename) {
     BSONObj matchPredicate = fromjson("{a: {$type: 16}}");
     const CollatorInterface* collator = nullptr;
     auto matcher = MatchExpressionParser::parse(matchPredicate, ExtensionsCallbackNoop(), collator);
@@ -1074,12 +1074,12 @@ TEST(SplitMatchExpression, ShouldNotMoveTypeAcrossRename) {
     std::pair<unique_ptr<MatchExpression>, unique_ptr<MatchExpression>> splitExpr =
         expression::splitMatchExpressionBy(std::move(matcher.getValue()), {}, renames);
 
-    ASSERT_FALSE(splitExpr.first.get());
+    ASSERT_TRUE(splitExpr.first.get());
+    BSONObjBuilder firstBob;
+    splitExpr.first->serialize(&firstBob);
+    ASSERT_BSONOBJ_EQ(firstBob.obj(), fromjson("{c: {$type: 16}}"));
 
-    ASSERT_TRUE(splitExpr.second.get());
-    BSONObjBuilder secondBob;
-    splitExpr.second->serialize(&secondBob);
-    ASSERT_BSONOBJ_EQ(secondBob.obj(), fromjson("{a: {$type: 16}}"));
+    ASSERT_FALSE(splitExpr.second.get());
 }
 
 TEST(SplitMatchExpression, ShouldNotMoveSizeAcrossRename) {
diff --git a/src/mongo/db/pipeline/pipeline_test.cpp b/src/mongo/db/pipeline/pipeline_test.cpp
index 68dfeb35bad..e38263b9785 100644
--- a/src/mongo/db/pipeline/pipeline_test.cpp
+++ b/src/mongo/db/pipeline/pipeline_test.cpp
@@ -837,6 +837,12 @@ TEST(PipelineOptimizationTest, MatchCannotMoveAcrossProjectRenameOfDottedPath) {
     assertPipelineOptimizesTo(inputPipe, outputPipe);
 }
 
+TEST(PipelineOptimizationTest, MatchWithTypeShouldMoveAcrossRename) {
+    string inputPipe = "[{$addFields: {a: '$b'}}, {$match: {a: {$type: 4}}}]";
+    string outputPipe = "[{$match: {b: {$type: 4}}}, {$addFields: {a: '$b'}}]";
+    assertPipelineOptimizesTo(inputPipe, outputPipe);
+}
+
 }  // namespace Local
 
 namespace Sharded {