PYTHON-4179: Optimize JSON decoding performance by avoiding object_pairs_hook (#1493)

Author: ilukyanchikov

bson/json_util.py

@@ -497,7 +497,11 @@ def loads(s: Union[str, bytes, bytearray], *args: Any, **kwargs: Any) -> Any:
        Accepts optional parameter `json_options`. See :class:`JSONOptions`.
     """
     json_options = kwargs.pop("json_options", DEFAULT_JSON_OPTIONS)
-    kwargs["object_pairs_hook"] = lambda pairs: object_pairs_hook(pairs, json_options)
+    # Execution time optimization if json_options.document_class is dict
+    if json_options.document_class is dict:
+        kwargs["object_hook"] = lambda obj: object_hook(obj, json_options)
+    else:
+        kwargs["object_pairs_hook"] = lambda pairs: object_pairs_hook(pairs, json_options)
     return json.loads(s, *args, **kwargs)
 
 

doc/contributors.rst

@@ -99,3 +99,4 @@ The following is a list of people who have contributed to
 - Iris Ho (sleepyStick)
 - Stephan Hof (stephan-hof)
 - Casey Clements (caseyclements)
+- Ivan Lukyanchikov (ilukyanchikov)