Fix null values handling in seeds (#437)

Co-authored-by: Noritaka Sekiyama <[email protected]>

CHANGELOG.md

@@ -6,6 +6,7 @@
 - Change GlueColumn parent from base Column to SparkColumn
 - Fix unraised DbtDatabaseError
 - Fix get_columns_in_relation function to stop returning additional partition columns
+- Fix null values handling in seeds
 - Fix exceptions import for FailedToConnectError and ExecutableError
 
 ## v1.8.1

dbt/adapters/glue/impl.py

@@ -1,4 +1,5 @@
 import io
+import json
 import os
 import re
 import uuid
@@ -535,7 +536,7 @@ def create_csv_table(self, model, agate_table):
 
         code = f'''
 custom_glue_code_for_dbt_adapter
-csv = {f.getvalue()}
+csv = {json.loads(f.getvalue())}
 df = spark.createDataFrame(csv)
 table_name = '{model["schema"]}.{model["name"]}'
 if (spark.sql("show tables in {model["schema"]}").where("tableName == '{model["name"]}'").count() > 0):