54 lines
1.6 KiB
Python
54 lines
1.6 KiB
Python
# coding: utf-8
|
|
"""
|
|
This modules implements custom types in SQLAlchemy.
|
|
"""
|
|
from __future__ import absolute_import, print_function, unicode_literals
|
|
|
|
import json
|
|
|
|
import sqlalchemy.types as types
|
|
|
|
|
|
class StringyJSON(types.TypeDecorator):
|
|
"""
|
|
Stores and retrieves JSON as TEXT for SQLite.
|
|
|
|
From
|
|
https://avacariu.me/articles/2016/compiling-json-as-text-for-sqlite-with-sqlalchemy.
|
|
|
|
.. note ::
|
|
|
|
The associated field is immutable. That is, changes to the data
|
|
(typically, changing the value of a dict field) will not trigger an
|
|
update on the SQL side upon ``commit`` as the reference to the object
|
|
will not have been updated. One should force the update by forcing an
|
|
update of the reference (by performing a ``copy`` operation on the dict
|
|
for instance).
|
|
"""
|
|
|
|
impl = types.TEXT
|
|
|
|
def process_bind_param(self, value, dialect):
|
|
"""
|
|
Process the bound param, serialize the object to JSON before saving
|
|
into database.
|
|
"""
|
|
if value is not None:
|
|
value = json.dumps(value)
|
|
return value
|
|
|
|
def process_result_value(self, value, dialect):
|
|
"""
|
|
Process the value fetched from the database, deserialize the JSON
|
|
string before returning the object.
|
|
"""
|
|
if value is not None:
|
|
value = json.loads(value)
|
|
return value
|
|
|
|
|
|
# TypeEngine.with_variant says "use StringyJSON instead when
|
|
# connecting to 'sqlite'"
|
|
# pylint: disable=locally-disabled,invalid-name
|
|
MagicJSON = types.JSON().with_variant(StringyJSON, "sqlite")
|