1 files changed, 10 insertions, 13 deletions

diff --git a/src/mongo/db/pipeline/field_path.h b/src/mongo/db/pipeline/field_path.h
index d2ee93734e7..c216bdbc0a4 100644
--- a/src/mongo/db/pipeline/field_path.h
+++ b/src/mongo/db/pipeline/field_path.h
@@ -69,9 +69,11 @@ public:
      *
      * Field names are validated using uassertValidFieldName().
      */
-    /* implicit */ FieldPath(std::string inputPath);
-    /* implicit */ FieldPath(StringData inputPath) : FieldPath(inputPath.toString()) {}
-    /* implicit */ FieldPath(const char* inputPath) : FieldPath(std::string(inputPath)) {}
+    /* implicit */ FieldPath(std::string inputPath, bool precomputeHashes = false);
+    /* implicit */ FieldPath(StringData inputPath, bool precomputeHashes = false)
+        : FieldPath(inputPath.toString(), precomputeHashes) {}
+    /* implicit */ FieldPath(const char* inputPath, bool precomputeHashes = false)
+        : FieldPath(std::string(inputPath), precomputeHashes) {}
 
     /**
      * Returns the number of path elements in the field path.
@@ -117,13 +119,8 @@ public:
      */
     HashedFieldName getFieldNameHashed(size_t i) const {
         dassert(i < getPathLength());
-        const auto begin = _fieldPathDotPosition[i] + 1;
-        const auto end = _fieldPathDotPosition[i + 1];
-        StringData fieldName{&_fieldPath[begin], end - begin};
-        if (_fieldHash[i] == kHashUninitialized) {
-            _fieldHash[i] = FieldNameHasher()(fieldName);
-        }
-        return HashedFieldName{fieldName, _fieldHash[i]};
+        invariant(_fieldHash[i] != kHashUninitialized);
+        return HashedFieldName{getFieldName(i), _fieldHash[i]};
     }
 
     /**
@@ -177,9 +174,9 @@ private:
     // lookup.
     std::vector<size_t> _fieldPathDotPosition;
 
-    // Contains the cached hash value for the field. Will initially be set to 'kHashUninitialized',
-    // and only generated when it is first retrieved via 'getFieldNameHashed'.
-    mutable std::vector<size_t> _fieldHash;
+    // Contains the hash value for the field names if it was requested when creating this path.
+    // Otherwise all elements are set to 'kHashUninitialized'.
+    std::vector<size_t> _fieldHash;
     static constexpr std::size_t kHashUninitialized = std::numeric_limits<std::size_t>::max();
 };