Fix caching in Series.applymap (#9821)

The cache key we were generating for these functions didn't take into account the constants that could be different in the bytecode. Hence certain functions were causing cache hits when they actually differ by a constant value somewhere in the logic.

Authors:
  - https://github.com/brandon-b-miller

Approvers:
  - GALI PREM SAGAR (https://github.com/galipremsagar)
  - Bradley Dice (https://github.com/bdice)
  - Ashwin Srinath (https://github.com/shwina)

URL: #9821

python/cudf/cudf/tests/test_udf_masked_ops.py

@@ -593,3 +593,22 @@ def func(row, c, k):
         return y
 
     run_masked_udf_test(func, data, args=(1, 2), check_dtype=False)
+
+
+def test_masked_udf_caching():
+    # Make sure similar functions that differ
+    # by simple things like constants actually
+    # recompile
+
+    data = cudf.Series([1, 2, 3])
+    expect = data ** 2
+    got = data.applymap(lambda x: x ** 2)
+
+    assert_eq(expect, got, check_dtype=False)
+
+    # update the constant value being used and make sure
+    # it does not result in a cache hit
+
+    expect = data ** 3
+    got = data.applymap(lambda x: x ** 3)
+    assert_eq(expect, got, check_dtype=False)

python/cudf/cudf/utils/cudautils.py

@@ -216,12 +216,14 @@ def make_cache_key(udf, sig):
     recompiling the same function for the same set of types
     """
     codebytes = udf.__code__.co_code
+    constants = udf.__code__.co_consts
     if udf.__closure__ is not None:
         cvars = tuple([x.cell_contents for x in udf.__closure__])
         cvarbytes = dumps(cvars)
     else:
         cvarbytes = b""
-    return codebytes, cvarbytes, sig
+
+    return constants, codebytes, cvarbytes, sig
 
 
 def compile_udf(udf, type_signature):