gistfile1.py

from sqlalchemy.ext.declarative import declarative_base
from history_meta import VersionedMeta, VersionedListener
from sqlalchemy import create_engine, Column, Integer, String, ForeignKey, DateTime
from sqlalchemy.orm import clear_mappers, compile_mappers, sessionmaker, deferred, MapperExtension
from sqlalchemy.sql.expression import text
from datetime import datetime
import time

engine = create_engine("postgresql+pg8000://postgres@localhost:25432/pruebas")
Base = declarative_base(metaclass=VersionedMeta, bind=engine)
Session = sessionmaker(extension=VersionedListener())

class UpdateExtension(MapperExtension):
	def after_update(self, mapper, connection, instance):
		testver_table = mapper.mapped_table
		connection.execute( testver_table.update( testver_table.c.id == instance.id ).values( last_update = text("NOW()")))

class SomeTable(Base):
	__tablename__ = "testver"
	__mapper_args__ = { 'extension':UpdateExtension()}
	id = Column( Integer, primary_key=True )
	name = Column( String(50) )
	created = Column( DateTime, server_default = text("NOW()") )
	last_update = Column( DateTime, server_default = text("NOW()") )
 

	def __init__(self, name = ""):
		self.name = name 

	def __repr__(self):
		return "<SomeTable( name = '%s') >"  % self.name


if __name__ == "__main__":
	Base.metadata.drop_all()
	Base.metadata.create_all()
	sess = Session()
	t = SomeTable( name = 'Domingo')
	sess.add(t)
	sess.commit()
	print t.version
	t.name = 'Aguilera'
	sess.commit()
	print t.version
	t.name = "Castillo"
	print t.version
	time.sleep(5)  #some time here
	sess.commit()
	for n in "earth wind fire water".split():
		t.name = n
		sess.commit()
		time.sleep(1)
	
	print t.id, t.name , t.created, t.version	
	print "=" * 50

	for row in engine.execute( "select id,version, name, last_update from testver_history union select id, version, name, last_update from testver order by id, version" ):
		print row[0], row[1], row[2], row[3]