Pass custom delimiter from Table.from_csv to BigQuery load

If our source table is loaded from CSV with no transformations, the
original source file will be directly loaded to GCS, we may need to
pass along a custom delimiter to BigQuery.

parsons/google/google_bigquery.py

@@ -782,6 +782,15 @@ def copy(
 
         self._validate_copy_inputs(if_exists=if_exists, data_type=data_type)
 
+        # If our source table is loaded from CSV with no transformations
+        # The original source file will be directly loaded to GCS
+        # We may need to pass along a custom delimiter to BigQuery
+        # Otherwise we use the default comma
+        if isinstance(tbl.table, petl.io.csv_py3.CSVView):
+            csv_delimiter = tbl.table.csvargs.get("delimiter", ",")
+        else:
+            csv_delimiter = ","
+
         job_config = self._process_job_config(
             job_config=job_config,
             destination_table_name=table_name,
@@ -796,6 +805,7 @@ def copy(
             allow_jagged_rows=allow_jagged_rows,
             quote=quote,
             custom_schema=schema,
+            csv_delimiter=csv_delimiter,
         )
 
         # Reorder schema to match table to ensure compatibility