ARROW-13943: [Python] Hide hash_aggregate functions from compute module

python/pyarrow/compute.py

@@ -244,6 +244,10 @@ def _make_global_functions():
     for cpp_name in reg.list_functions():
         name = rewrites.get(cpp_name, cpp_name)
         func = reg.get_function(cpp_name)
+        if func.kind == "hash_aggregate":
+            # Hash aggregate functions are not callable,
+            # so let's not expose them at module level.
+            continue
         assert name not in g, name
         g[cpp_name] = g[name] = _wrap_function(name, func)
 

python/pyarrow/tests/test_compute.py

@@ -96,6 +96,14 @@ def test_exported_functions():
             func(*args)
 
 
+def test_hash_aggregate_not_exported():
+    # Ensure we are not leaking hash aggregate functions
+    # which are not callable by themselves.
+    for func in exported_functions:
+        arrow_f = pc.get_function(func.__arrow_compute_function__["name"])
+        assert arrow_f.kind != "hash_aggregate"
+
+
 def test_exported_option_classes():
     classes = exported_option_classes
     assert len(classes) >= 10
@@ -241,7 +249,11 @@ def test_pickle_functions():
 def test_pickle_global_functions():
     # Pickle global wrappers (manual or automatic) of registered functions
     for name in pc.list_functions():
-        func = getattr(pc, name)
+        try:
+            func = getattr(pc, name)
+        except AttributeError:
+            # hash_aggregate functions are not exported as callables.
+            continue
         reconstructed = pickle.loads(pickle.dumps(func))
         assert reconstructed is func