fix: write to file in CSV format, not in JSON

writing in JSON format does not make sense.

The records in Postgres should arrive exactly as they were scraped by a
Tap at the source.

E.g. if a string in the sources has control characters like LF (0x0a),
the same string should also have LF in the postgres target and not '\n'
like JSON format uses.

Fixes transferwise#131

target_postgres/__init__.py

@@ -1,6 +1,7 @@
 #!/usr/bin/env python3
 
 import argparse
+import csv
 import io
 import json
 import os
@@ -344,10 +345,14 @@ def flush_records(stream, records_to_load, row_count, db_sync, temp_dir=None):
 
     size_bytes = 0
     csv_fd, csv_file = mkstemp(suffix='.csv', prefix=f'{stream}_', dir=temp_dir)
-    with open(csv_fd, 'w+b') as f:
+    with open(csv_fd, 'w') as csvfile:
+        writer = csv.DictWriter(
+            csvfile,
+            fieldnames=list(db_sync.flatten_schema.keys()),
+            extrasaction='ignore',
+        )
         for record in records_to_load.values():
-            csv_line = db_sync.record_to_csv_line(record)
-            f.write(bytes(csv_line + '\n', 'UTF-8'))
+            writer.writerow(db_sync.record_to_flattened_record(record))
 
     size_bytes = os.path.getsize(csv_file)
     db_sync.load_csv(csv_file, row_count, size_bytes)

target_postgres/db_sync.py

@@ -1,13 +1,15 @@
 import json
 import sys
-import psycopg2
-import psycopg2.extras
-import inflection
 import re
 import uuid
 import itertools
 import time
 from collections.abc import MutableMapping
+from typing import Dict
+
+import psycopg2
+import psycopg2.extras
+import inflection
 from singer import get_logger
 
 
@@ -344,15 +346,8 @@ def record_primary_key_string(self, record):
             raise exc
         return ','.join(key_props)
 
-    def record_to_csv_line(self, record):
-        flatten = flatten_record(record, self.flatten_schema, max_level=self.data_flattening_max_level)
-        return ','.join(
-            [
-                json.dumps(flatten[name], ensure_ascii=False)
-                if name in flatten and (flatten[name] == 0 or flatten[name]) else ''
-                for name in self.flatten_schema
-            ]
-        )
+    def record_to_flattened_record(self, record: Dict) -> Dict:
+        return flatten_record(record, self.flatten_schema, max_level=self.data_flattening_max_level)
 
     def load_csv(self, file, count, size_bytes):
         stream_schema_message = self.stream_schema_message
@@ -367,7 +362,7 @@ def load_csv(self, file, count, size_bytes):
                 temp_table = self.table_name(stream_schema_message['stream'], is_temporary=True)
                 cur.execute(self.create_table_query(table_name=temp_table, is_temporary=True))
 
-                copy_sql = "COPY {} ({}) FROM STDIN WITH (FORMAT CSV, ESCAPE '\\')".format(
+                copy_sql = "COPY {} ({}) FROM STDIN WITH (FORMAT CSV)".format(
                     temp_table,
                     ', '.join(self.column_names())
                 )