SERVER-10159 Re-serialize and cache dotted form in FieldRef on request

1 files changed, 14 insertions, 11 deletions

diff --git a/src/mongo/db/field_ref.h b/src/mongo/db/field_ref.h
index 681f9873932..06e60c2c165 100644
--- a/src/mongo/db/field_ref.h
+++ b/src/mongo/db/field_ref.h
@@ -90,7 +90,7 @@ namespace mongo {
          * Returns a copy of the full dotted field in its current state (i.e., some parts may
          * have been replaced since the parse() call).
          */
-        std::string dottedField( size_t offset = 0 ) const;
+        StringData dottedField( size_t offsetFromStart = 0 ) const;
 
         /**
          * Compares the full dotted path represented by this FieldRef to other
@@ -117,12 +117,6 @@ namespace mongo {
          */
         size_t numParts() const { return _size; }
 
-        /**
-         * Returns the number of fields parts that were replaced so far. Replacing the same
-         * fields several times only counts for 1.
-         */
-        size_t numReplaced() const;
-
     private:
         // Dotted fields are most often not longer than four parts. We use a mixed structure
         // here that will not require any extra memory allocation when that is the case. And
@@ -139,20 +133,29 @@ namespace mongo {
          */
         size_t appendPart(const StringData& part);
 
+        /**
+         * Re-assemble _dotted from components, including any replacements in _replacements,
+         * and update the StringData components in _fixed and _variable to refer to the parts
+         * of the new _dotted. This is used to make the storage for the current value of this
+         * FieldRef contiguous so it can be returned as a StringData from the dottedField
+         * method above.
+         */
+        void reserialize() const;
+
         // number of field parts stored
         size_t _size;
 
         // first kResevedAhead field components
-        StringData _fixed[kReserveAhead];
+        mutable StringData _fixed[kReserveAhead];
 
          // remaining field components
-        std::vector<StringData> _variable;
+        mutable std::vector<StringData> _variable;
 
         // cached dotted name
-        std::string _dotted;
+        mutable std::string _dotted;
 
         // back memory added with the setPart call pointed to by _fized and _variable
-        std::vector<std::string> _replacements;
+        mutable std::vector<std::string> _replacements;
     };
 
     inline bool operator==(const FieldRef& lhs, const FieldRef& rhs) {