[GitHub] [spark] xinrong-meng commented on a diff in pull request #41026: [SPARK-43132] [SS] [CONNECT] Add DataStreamWriter foreach() API

["xinrong-meng (via GitHub)" <gi...@apache.org>]

xinrong-meng commented on code in PR #41026:
URL: https://github.com/apache/spark/pull/41026#discussion_r1190166838


##########
python/pyspark/sql/utils.py:
##########
@@ -119,6 +124,79 @@ class Java:
         implements = ["org.apache.spark.sql.execution.streaming.sources.PythonForeachBatchFunction"]
 
 
+def construct_foreach_function(f: Union[Callable[[Row], None], "SupportsProcess"]):
+    from pyspark.taskcontext import TaskContext
+
+    if callable(f):
+        # The provided object is a callable function that is supposed to be called on each row.
+        # Construct a function that takes an iterator and calls the provided function on each
+        # row.
+        def func_without_process(_: Any, iterator: Iterator) -> Iterator:
+            for x in iterator:
+                f(x)  # type: ignore[operator]
+            return iter([])
+
+        return func_without_process
+
+    else:
+        # The provided object is not a callable function. Then it is expected to have a
+        # 'process(row)' method, and optional 'open(partition_id, epoch_id)' and
+        # 'close(error)' methods.
+
+        if not hasattr(f, "process"):
+            raise AttributeError("Provided object does not have a 'process' method")

Review Comment:
   How about raising a `PySparkAttributeError`?



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