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