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:

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

from sqlalchemy_continuum import make_versioned


make_versioned(user_cls=None)


class Article(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 database
article.versions[0].name
# 'Some article'

article.name = 'Updated name'
session.commit()

article.versions[1].name
# 'Updated name'


# lets revert back to first version
article.versions[0].revert()

article.name
# 'Some article'

For completeness, below is a working example.

from sqlalchemy_continuum import make_versioned
from sqlalchemy import Column, Integer, Unicode, UnicodeText, create_engine
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import create_session, configure_mappers

make_versioned(user_cls=None)

Base = declarative_base()
class Article(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].name
article.name = u'Updated name'
session.commit()
article.versions[1].name
article.versions[0].revert()
article.name

Resources

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

License

anthraxx/sqlalchemy-continuum

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