SERVER-15029: missing rename source field should be a no-op

2 files changed, 19 insertions, 1 deletions

diff --git a/src/mongo/db/ops/modifier_rename.cpp b/src/mongo/db/ops/modifier_rename.cpp
index d603ff9da0f..c2a86e5cb0d 100644
--- a/src/mongo/db/ops/modifier_rename.cpp
+++ b/src/mongo/db/ops/modifier_rename.cpp
@@ -146,8 +146,11 @@ namespace mongo {
                                                        &fromIdxFound,
                                                        &_preparedState->fromElemFound);
 
+        const bool sourceExists = (_preparedState->fromElemFound.ok() &&
+                                   fromIdxFound == (_fromFieldRef.numParts() - 1));
+
         // If we can't find the full element in the from field then we can't do anything.
-        if (!status.isOK()) {
+        if (!status.isOK() || !sourceExists) {
             execInfo->noOp = true;
             _preparedState->fromElemFound = root.getDocument().end();
 
diff --git a/src/mongo/db/ops/modifier_rename_test.cpp b/src/mongo/db/ops/modifier_rename_test.cpp
index 0c1b3310264..606337bdd7c 100644
--- a/src/mongo/db/ops/modifier_rename_test.cpp
+++ b/src/mongo/db/ops/modifier_rename_test.cpp
@@ -121,6 +121,21 @@ namespace {
         ASSERT_EQUALS(logDoc, logObj);
     }
 
+    TEST(MissingFromDotted, InitPrepLog) {
+        Document doc(fromjson("{a: {r:2}}"));
+        Mod setMod(fromjson("{$rename: {'a.b':'a.c'}}"));
+
+        ModifierInterface::ExecInfo execInfo;
+        ASSERT_OK(setMod.prepare(doc.root(), "", &execInfo));
+        ASSERT_TRUE(execInfo.noOp);
+
+        Document logDoc;
+        LogBuilder logBuilder(logDoc.root());
+        BSONObj logObj = fromjson("{}");
+        ASSERT_OK(setMod.log(&logBuilder));
+        ASSERT_EQUALS(logDoc, logObj);
+    }
+
     TEST(BasicInit, DifferentRoots) {
         Document doc(fromjson("{a: 2}"));
         Mod setMod(fromjson("{$rename: {'a':'f.g'}}"));