SQLAlchemy-Continuum

Versioning and auditing extension for SQLAlchemy.

Features

• Creates versions for inserts, deletes and updates
• Does not store updates which don't change anything
• Supports alembic migrations
• Can revert objects data as well as all object relations at given transaction even if the object was deleted
• Transactions can be queried afterwards using SQLAlchemy query syntax
• Query for changed records at given transaction
• Temporal relationship reflection. Version object's relationship show the parent objects relationships as they where in that point in time.
• Supports native versioning for PostgreSQL database (trigger based versioning)

QuickStart

pip install SQLAlchemy-Continuum

In order to make your models versioned you need two things:

1. Call make_versioned() before your models are defined.
2. Add __versioned__ to all models you wish to add versioning to

fromsqlalchemy_continuumimportmake_versionedmake_versioned(user_cls=None)
classArticle(Base):
__versioned__= {}
__tablename__='article'id=sa.Column(sa.Integer, primary_key=True, autoincrement=True)
name=sa.Column(sa.Unicode(255))
content=sa.Column(sa.UnicodeText)
article=Article(name='Some article', content='Some content')
session.add(article)
session.commit()
# article has now one version stored in databasearticle.versions[0].name# 'Some article'article.name='Updated name'session.commit()
article.versions[1].name# 'Updated name'# lets revert back to first versionarticle.versions[0].revert()
article.name# 'Some article'

For completeness, below is a working example.

fromsqlalchemy_continuumimportmake_versionedfromsqlalchemyimportColumn, Integer, Unicode, UnicodeText, create_enginefromsqlalchemy.ext.declarativeimportdeclarative_basefromsqlalchemy.ormimportcreate_session, configure_mappersmake_versioned(user_cls=None)
Base=declarative_base()
classArticle(Base):
__versioned__= {}
__tablename__='article'id=Column(Integer, primary_key=True, autoincrement=True)
name=Column(Unicode(255))
content=Column(UnicodeText)
configure_mappers()
engine=create_engine('sqlite://')
Base.metadata.create_all(engine)
session=create_session(bind=engine, autocommit=False)
article=Article(name=u'Some article', content=u'Some content')
session.add(article)
session.commit()
article.versions[0].namearticle.name=u'Updated name'session.commit()
article.versions[1].namearticle.versions[0].revert()
article.name

Resources

• Documentation
• Issue Tracker
• Code

More information

• http://en.wikipedia.org/wiki/Slowly_changing_dimension
• http://en.wikipedia.org/wiki/Change_data_capture
• http://en.wikipedia.org/wiki/Anchor_Modeling
• http://en.wikipedia.org/wiki/Shadow_table
• https://wiki.postgresql.org/wiki/Audit_trigger
• https://wiki.postgresql.org/wiki/Audit_trigger_91plus
• http://kosalads.blogspot.fi/2014/06/implement-audit-functionality-in.html
• https://github.com/2ndQuadrant/pgaudit