working subgraphs in workflow

nvtabular/workflow/workflow.py

@@ -142,6 +142,10 @@ def fit_schema(self, input_schema: Schema):
         self.graph.construct_schema(input_schema)
         return self
 
+    @property
+    def subworkflows(self):
+        return list(self.graph.subgraphs.keys())
+
     @property
     def input_dtypes(self):
         return self.graph.input_dtypes
@@ -165,6 +169,10 @@ def output_node(self):
     def _input_columns(self):
         return self.graph._input_columns()
 
+    def get_subworkflow(self, subgraph_name):
+        subgraph = self.graph.subgraph(subgraph_name)
+        return Workflow(subgraph.output_node)
+
     def remove_inputs(self, input_cols) -> "Workflow":
         """Removes input columns from the workflow.
 

tests/unit/workflow/test_workflow_subgraphs.py

@@ -0,0 +1,99 @@
+#
+# Copyright (c) 2023, NVIDIA CORPORATION.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+
+import os
+
+import numpy as np
+import pytest
+from pandas.api.types import is_integer_dtype
+
+from merlin.core.utils import set_dask_client
+from merlin.dag.ops.subgraph import Subgraph
+from nvtabular import Workflow, ops
+from tests.conftest import assert_eq
+
+
+@pytest.mark.parametrize("gpu_memory_frac", [0.01, 0.1])
+@pytest.mark.parametrize("engine", ["parquet", "csv", "csv-no-header"])
+@pytest.mark.parametrize("dump", [True, False])
+@pytest.mark.parametrize("replace", [True, False])
+def test_workflow_subgraphs(tmpdir, client, df, dataset, gpu_memory_frac, engine, dump, replace):
+    cat_names = ["name-cat", "name-string"] if engine == "parquet" else ["name-string"]
+    cont_names = ["x", "y", "id"]
+    label_name = ["label"]
+
+    norms = ops.Normalize()
+    cat_features = cat_names >> ops.Categorify()
+    if replace:
+        cont_features = cont_names >> ops.FillMissing() >> ops.LogOp >> norms
+    else:
+        fillmissing_logop = (
+            cont_names
+            >> ops.FillMissing()
+            >> ops.LogOp
+            >> ops.Rename(postfix="_FillMissing_1_LogOp_1")
+        )
+        cont_features = cont_names + fillmissing_logop >> norms
+
+    set_dask_client(client=client)
+    wkflow_ops = Subgraph("cat_graph", cat_features) + Subgraph("cont_graph", cont_features)
+    workflow = Workflow(wkflow_ops + label_name)
+
+    workflow.fit(dataset)
+
+    if dump:
+        workflow_dir = os.path.join(tmpdir, "workflow")
+        workflow.save(workflow_dir)
+        workflow = None
+
+        workflow = Workflow.load(workflow_dir)
+
+    def get_norms(tar):
+        ser_median = tar.dropna().quantile(0.5, interpolation="linear")
+        gdf = tar.fillna(ser_median)
+        gdf = np.log(gdf + 1)
+        return gdf
+
+    concat_ops = "_FillMissing_1_LogOp_1"
+    if replace:
+        concat_ops = ""
+
+    df_pp = workflow.transform(dataset).to_ddf().compute()
+
+    if engine == "parquet":
+        assert is_integer_dtype(df_pp["name-cat"].dtype)
+    assert is_integer_dtype(df_pp["name-string"].dtype)
+
+    subgraph_cat = workflow.get_subworkflow("cat_graph")
+    subgraph_cont = workflow.get_subworkflow("cont_graph")
+    assert isinstance(subgraph_cat, Workflow)
+    assert isinstance(subgraph_cont, Workflow)
+    # will not be the same nodes of saved out and loaded back
+    if not dump:
+        assert subgraph_cat.output_node == cat_features
+        assert subgraph_cont.output_node == cont_features
+    # check failure path works as expected
+    with pytest.raises(ValueError) as exc:
+        workflow.get_subworkflow("not_exist")
+    assert "No subgraph named" in str(exc.value)
+
+    # test transform results from subgraph
+    sub_cat_df = subgraph_cat.transform(dataset).to_ddf().compute()
+    assert_eq(sub_cat_df, df_pp[cat_names])
+
+    cont_names = [name + concat_ops for name in cont_names]
+    sub_cont_df = subgraph_cont.transform(dataset).to_ddf().compute()
+    assert_eq(sub_cont_df[cont_names], df_pp[cont_names])