SERVER-27992 Use UUIDs for replication

3 files changed, 47 insertions, 0 deletions

diff --git a/src/mongo/bson/bson_obj_test.cpp b/src/mongo/bson/bson_obj_test.cpp
index 890d3c4580f..5a9360605d5 100644
--- a/src/mongo/bson/bson_obj_test.cpp
+++ b/src/mongo/bson/bson_obj_test.cpp
@@ -608,4 +608,24 @@ TEST(BSONObj, ShareOwnershipWith) {
     ASSERT_BSONOBJ_EQ(obj, BSON("a" << 1));
 }
 
+TEST(BSONObj, addField) {
+    auto obj = BSON("a" << 1 << "b" << 2);
+
+    // Check that replacing a field maintains the same ordering and doesn't add a field.
+    auto objA2 = BSON("a" << 2);
+    auto elemA2 = objA2.firstElement();
+    auto addFieldA2 = obj.addField(elemA2);
+    ASSERT_EQ(addFieldA2.nFields(), 2);
+    ASSERT_BSONOBJ_EQ(addFieldA2, BSON("a" << 2 << "b" << 2));
+
+    // Check that adding a new field places it at the end.
+    auto objC3 = BSON("c" << 3);
+    auto elemC3 = objC3.firstElement();
+    auto addFieldC3 = obj.addField(elemC3);
+    ASSERT_BSONOBJ_EQ(addFieldC3, BSON("a" << 1 << "b" << 2 << "c" << 3));
+
+    // Check that after all this obj is unchanged.
+    ASSERT_BSONOBJ_EQ(obj, BSON("a" << 1 << "b" << 2));
+}
+
 }  // unnamed namespace
diff --git a/src/mongo/bson/bsonobj.cpp b/src/mongo/bson/bsonobj.cpp
index 2f7133a2a63..06f446c9c05 100644
--- a/src/mongo/bson/bsonobj.cpp
+++ b/src/mongo/bson/bsonobj.cpp
@@ -503,6 +503,26 @@ bool BSONObj::getObjectID(BSONElement& e) const {
     return false;
 }
 
+BSONObj BSONObj::addField(const BSONElement& field) const {
+    if (!field.ok())
+        return copy();
+    BSONObjBuilder b;
+    StringData name = field.fieldNameStringData();
+    bool added = false;
+    for (auto e : *this) {
+        if (e.fieldNameStringData() == name) {
+            if (!added)
+                b.append(field);
+            added = true;
+        } else {
+            b.append(e);
+        }
+    }
+    if (!added)
+        b.append(field);
+    return b.obj();
+}
+
 BSONObj BSONObj::removeField(StringData name) const {
     BSONObjBuilder b;
     BSONObjIterator i(*this);
diff --git a/src/mongo/bson/bsonobj.h b/src/mongo/bson/bsonobj.h
index 8d62bc8fd3d..15e2326c0db 100644
--- a/src/mongo/bson/bsonobj.h
+++ b/src/mongo/bson/bsonobj.h
@@ -245,6 +245,13 @@ public:
     /** note: addFields always adds _id even if not specified */
     int addFields(BSONObj& from, std::set<std::string>& fields); /* returns n added */
 
+    /**
+     * Add specific field to the end of the object if it did not exist, otherwise replace it
+     * preserving original field order. Returns newly built object. Returns copy of this for empty
+     * field.
+     */
+    BSONObj addField(const BSONElement& field) const;
+
     /** remove specified field and return a new object with the remaining fields.
         slowish as builds a full new object
      */