diff --git a/swh/core/db/__init__.py b/swh/core/db/__init__.py
index 5e21052..c4085bf 100644
--- a/swh/core/db/__init__.py
+++ b/swh/core/db/__init__.py
@@ -1,160 +1,162 @@
 # Copyright (C) 2015-2019  The Software Heritage developers
 # See the AUTHORS file at the top-level directory of this distribution
 # License: GNU General Public License version 3, or any later version
 # See top-level LICENSE file for more information
 
 import binascii
 import datetime
 import enum
 import json
 import os
 import threading
 
 from contextlib import contextmanager
 
 import psycopg2
 import psycopg2.extras
 
 
 psycopg2.extras.register_uuid()
 
 
+def escape(data):
+    if data is None:
+        return ''
+    if isinstance(data, bytes):
+        return '\\x%s' % binascii.hexlify(data).decode('ascii')
+    elif isinstance(data, str):
+        return '"%s"' % data.replace('"', '""')
+    elif isinstance(data, datetime.datetime):
+        # We escape twice to make sure the string generated by
+        # isoformat gets escaped
+        return escape(data.isoformat())
+    elif isinstance(data, dict):
+        return escape(json.dumps(data))
+    elif isinstance(data, list):
+        return escape("{%s}" % ','.join(escape(d) for d in data))
+    elif isinstance(data, psycopg2.extras.Range):
+        # We escape twice here too, so that we make sure
+        # everything gets passed to copy properly
+        return escape(
+            '%s%s,%s%s' % (
+                '[' if data.lower_inc else '(',
+                '-infinity' if data.lower_inf else escape(data.lower),
+                'infinity' if data.upper_inf else escape(data.upper),
+                ']' if data.upper_inc else ')',
+            )
+        )
+    elif isinstance(data, enum.IntEnum):
+        return escape(int(data))
+    else:
+        # We don't escape here to make sure we pass literals properly
+        return str(data)
+
+
 class BaseDb:
     """Base class for swh.*.*Db.
 
     cf. swh.storage.db.Db, swh.archiver.db.ArchiverDb
 
     """
 
     @classmethod
     def connect(cls, *args, **kwargs):
         """factory method to create a DB proxy
 
         Accepts all arguments of psycopg2.connect; only some specific
         possibilities are reported below.
 
         Args:
             connstring: libpq2 connection string
 
         """
         conn = psycopg2.connect(*args, **kwargs)
         return cls(conn)
 
     @classmethod
     def from_pool(cls, pool):
         return cls(pool.getconn(), pool=pool)
 
     def _cursor(self, cur_arg):
         """get a cursor: from cur_arg if given, or a fresh one otherwise
 
         meant to avoid boilerplate if/then/else in methods that proxy stored
         procedures
 
         """
         if cur_arg is not None:
             return cur_arg
         else:
             return self.conn.cursor()
 
     def __init__(self, conn, pool=None):
         """create a DB proxy
 
         Args:
             conn: psycopg2 connection to the SWH DB
             pool: psycopg2 pool of connections
 
         """
         self.conn = conn
         self.pool = pool
 
     def __del__(self):
         if self.pool:
             self.pool.putconn(self.conn)
 
     @contextmanager
     def transaction(self):
         """context manager to execute within a DB transaction
 
         Yields:
             a psycopg2 cursor
 
         """
         with self.conn.cursor() as cur:
             try:
                 yield cur
                 self.conn.commit()
             except Exception:
                 if not self.conn.closed:
                     self.conn.rollback()
                 raise
 
     def copy_to(self, items, tblname, columns, cur=None, item_cb=None):
         """Copy items' entries to table tblname with columns information.
 
         Args:
             items (dict): dictionary of data to copy over tblname
             tblname (str): Destination table's name
             columns ([str]): keys to access data in items and also the
               column names in the destination table.
             item_cb (fn): optional function to apply to items's entry
 
         """
-        def escape(data):
-            if data is None:
-                return ''
-            if isinstance(data, bytes):
-                return '\\x%s' % binascii.hexlify(data).decode('ascii')
-            elif isinstance(data, str):
-                return '"%s"' % data.replace('"', '""')
-            elif isinstance(data, datetime.datetime):
-                # We escape twice to make sure the string generated by
-                # isoformat gets escaped
-                return escape(data.isoformat())
-            elif isinstance(data, dict):
-                return escape(json.dumps(data))
-            elif isinstance(data, list):
-                return escape("{%s}" % ','.join(escape(d) for d in data))
-            elif isinstance(data, psycopg2.extras.Range):
-                # We escape twice here too, so that we make sure
-                # everything gets passed to copy properly
-                return escape(
-                    '%s%s,%s%s' % (
-                        '[' if data.lower_inc else '(',
-                        '-infinity' if data.lower_inf else escape(data.lower),
-                        'infinity' if data.upper_inf else escape(data.upper),
-                        ']' if data.upper_inc else ')',
-                    )
-                )
-            elif isinstance(data, enum.IntEnum):
-                return escape(int(data))
-            else:
-                # We don't escape here to make sure we pass literals properly
-                return str(data)
 
         read_file, write_file = os.pipe()
 
         def writer():
             cursor = self._cursor(cur)
             with open(read_file, 'r') as f:
                 cursor.copy_expert('COPY %s (%s) FROM STDIN CSV' % (
                     tblname, ', '.join(columns)), f)
 
         write_thread = threading.Thread(target=writer)
         write_thread.start()
 
         try:
             with open(write_file, 'w') as f:
                 for d in items:
                     if item_cb is not None:
                         item_cb(d)
                     line = [escape(d.get(k)) for k in columns]
                     f.write(','.join(line))
                     f.write('\n')
         finally:
             # No problem bubbling up exceptions, but we still need to make sure
             # we finish copying, even though we're probably going to cancel the
             # transaction.
             write_thread.join()
 
     def mktemp(self, tblname, cur=None):
         self._cursor(cur).execute('SELECT swh_mktemp(%s)', (tblname,))