NoSQL Versioning

A Python library for NoSQL record versioning.

Installation

To install the latest release on PyPi, simply run:

pip install nosql_versioning

Or to install the latest development version, run:

git clone https://github.com/xinhuang/nosql_versioning.git
cd nosql_versioning
python setup.py install

Quick Tutorial

>>> from nosql_versioning import schema
>>> import json
>>>
>>> version, Record = schema(decode=json.loads)
>>>
>>> @version()
>>> class Recordv0(object):
>>>     def __init__(self, data):
>>>         self.old_name = data['old_name']
>>>
>>> @version(1)
>>> class Recordv1(object):
>>>     def __init__(self, value=None, *args, data=None):
>>>         if data:
>>>             self.new_name = data['new_name']
>>>         else:
>>>             self.new_name = value
>>>
>>>     @staticmethod
>>>     def migrate(data):
>>>         data['new_name'] = data['old_name']
>>>         del data['old_name']
>>>
>>>     @staticmethod
>>>     def a_staticmethod(n):
>>>         print(n * 2)
>>>
>>> rec = Record('{"_ver": 0, "old_name": 1}')
>>> print(rec.new_name)
1
>>> rec = Record(value=42)         # custom constructor can also be used
>>> print(rec.new_name)
42
>>> Record.a_staticmethod(42)      # static methods defined in the latest version can be used
84

API Reference

schema(decode=decode, version=get_version)

Create a class descriptor to specify record classes of different version, and a Record initializer to instantiate the latest record from data, or to migrate data to the latest version.

Args:	decode: Deserialize objects retrieved from database. By default no decoding will be applied. version: Get version from record. By default it's data.get('_ver')
Returns:	version: A class descriptor to specify record version. Record: A initializer that to construct defined Record class. Migrate if data is not the latest version.

version(n=0)

A class descriptor to specify record class of version N.

Args:	n: Version. Must be a integer.
Raises:	VersionConflictionException: When a version is defined twice.

Record(data=None, *args, **kwargs)

The initializer to migrate record to latest and instantiate record class.

Args:	data: If only this argument is specified, decode(data) will be used to instantiate the latest record class. (Migrate if needed.) args, kwargs: If not only data is specified, all arguments will be passed to instantiate the latest record class. No migration.

Migration from Version N-1 to N will use static method migrate in record class version N.

In case there is no version specified, migration from None to 0 will use static method migrate in record class Version 0.

Licensing

This project is released under the terms of the MIT Open Source License. View LICENSE.txt for more information.