leewyang commented on code in PR #37734:
URL: https://github.com/apache/spark/pull/37734#discussion_r1015893038


##########
python/pyspark/ml/functions.py:
##########
@@ -106,6 +117,543 @@ def array_to_vector(col: Column) -> Column:
     return 
Column(sc._jvm.org.apache.spark.ml.functions.array_to_vector(_to_java_column(col)))
 
 
+def _batched(
+    data: pd.Series | pd.DataFrame | Tuple[pd.Series], batch_size: int
+) -> Iterator[pd.DataFrame]:
+    """Generator that splits a pandas dataframe/series into batches."""
+    if isinstance(data, pd.DataFrame):
+        df = data
+    elif isinstance(data, pd.Series):
+        df = pd.concat((data,), axis=1)
+    else:  # isinstance(data, Tuple[pd.Series]):
+        df = pd.concat(data, axis=1)
+
+    index = 0
+    data_size = len(df)
+    while index < data_size:
+        yield df.iloc[index : index + batch_size]
+        index += batch_size
+
+
+def _is_tensor_col(data: pd.Series | pd.DataFrame) -> bool:
+    if isinstance(data, pd.Series):
+        return data.dtype == np.object_ and isinstance(data.iloc[0], 
(np.ndarray, list))
+    elif isinstance(data, pd.DataFrame):
+        return any(data.dtypes == np.object_) and any(
+            [isinstance(d, (np.ndarray, list)) for d in data.iloc[0]]
+        )
+    else:
+        raise ValueError(
+            "Unexpected data type: {}, expected pd.Series or 
pd.DataFrame.".format(type(data))
+        )
+
+
+def _has_tensor_cols(data: pd.Series | pd.DataFrame | Tuple[pd.Series]) -> 
bool:
+    """Check if input Series/DataFrame/Tuple contains any tensor-valued 
columns."""
+    if isinstance(data, (pd.Series, pd.DataFrame)):
+        return _is_tensor_col(data)
+    else:  # isinstance(data, Tuple):
+        return any(_is_tensor_col(elem) for elem in data)
+
+
+def _validate_and_transform(
+    preds: np.ndarray | Mapping[str, np.ndarray] | List[Mapping[str, Any]],
+    num_input_rows: int,
+    return_type: DataType,
+) -> pd.DataFrame | pd.Series:
+    """Validate numpy-based model predictions against the expected pandas_udf 
return_type and
+    transforms the predictions into an equivalent pandas DataFrame or 
Series."""
+    if isinstance(return_type, StructType):
+        struct_rtype: StructType = return_type
+        fieldNames = struct_rtype.names
+        if isinstance(preds, dict):
+            # dictionary of columns
+            predNames = list(preds.keys())
+            for field in struct_rtype.fields:
+                if len(preds[field.name]) != num_input_rows:
+                    raise ValueError("Prediction results must have same length 
as input data.")
+                if field.dataType == ArrayType and preds[field.name].shape != 
2:

Review Comment:
   Good catch.  Fixed and added test case.



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