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Signed-off-by: Revital Sur <[email protected]>

afm/server.py

@@ -61,6 +61,11 @@ def _write_asset(self, asset, reader, write_mode):
         # in this implementation we currently begin by reading the entire dataset
         record_batches = reader.read_all().combine_chunks().to_batches()
         transformed_batches = transform_batches(asset.actions, record_batches)
+        # If the client request to append to the existing data then the flag `overwrite_or_ignore` is used
+        # with a basename_template that is related to the time of writing. This operation writes the data
+        # to a new file while ignoring (not changing) the existed files.
+        # Otherwise, the flag `delete_mathing` is used. This operation writes the data to a new file
+        # while deleting the existed files.
         if write_mode == "append":
             logger.trace("write_mode: append", extra={DataSetID: asset.name, ForUser: True})
             ds.write_dataset(transformed_batches, base_dir=asset.path, basename_template="part-{:%Y-%m-%d-%H-%M-%S-%f}-{{i}}.parquet".format(datetime.datetime.now()), format=asset.format,  filesystem=asset.filesystem, existing_data_behavior='overwrite_or_ignore')