Pass custom delimiter from Table.from_csv to BigQuery load (#1083)

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

@@ -787,6 +787,15 @@ 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,
@@ -801,6 +810,7 @@ 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