Don't create _join_functions (#32336)

Author: dsaxton

pandas/core/reshape/merge.py

@@ -1312,7 +1312,12 @@ def _get_join_indexers(
     kwargs = copy.copy(kwargs)
     if how == "left":
         kwargs["sort"] = sort
-    join_func = _join_functions[how]
+    join_func = {
+        "inner": libjoin.inner_join,
+        "left": libjoin.left_outer_join,
+        "right": _right_outer_join,
+        "outer": libjoin.full_outer_join,
+    }[how]
 
     return join_func(lkey, rkey, count, **kwargs)
 
@@ -1842,14 +1847,6 @@ def _right_outer_join(x, y, max_groups):
     return left_indexer, right_indexer
 
 
-_join_functions = {
-    "inner": libjoin.inner_join,
-    "left": libjoin.left_outer_join,
-    "right": _right_outer_join,
-    "outer": libjoin.full_outer_join,
-}
-
-
 def _factorize_keys(lk, rk, sort=True):
     # Some pre-processing for non-ndarray lk / rk
     if is_datetime64tz_dtype(lk) and is_datetime64tz_dtype(rk):