Ticket #324: lastupdated.py

from axiom import attributes, item, store
from epsilon.extime import Time

class MyAxiomLastUpdatedAttribute(attributes.timestamp):
    def __init__(self, **kw):
        super(MyAxiomLastUpdatedAttribute, self).__init__(**kw)
        if kw.has_key('default'):
            self.default = self.infilter(kw['default'], None)
      
class ItemWithTriggersMixin(object):
    triggers = []
    def __init__(self, **kw):
        super(ItemWithTriggersMixin, self).__init__(**kw)
        for triggerSql in self.getTriggers():
            self.store.createSQL(triggerSql)
      
class ItemWithAutoLastUpdatedStampMixin(ItemWithTriggersMixin):        
    def getTriggers(self):
#        I use strftime("%%s","now") * %(MICRO)d but it has a resolution of 1 second
#        as opposed to extime whose resolution is microseconds.
        return [
            """
            CREATE TRIGGER update_%(table)s_lastUpdated UPDATE OF %(othercols)s ON %(table)s 
            BEGIN
                UPDATE %(table)s SET %(lucol)s = strftime("%%s","now") * %(MICRO)d WHERE oid = OLD.oid;
            END;
            """ % dict(
                table     = self.getTableName(),
                lucol     = self.__class__.lastUpdated.columnName,
                othercols = ",".join(v.columnName for k,v in self.getSchema() if k != "lastUpdated"),
                MICRO     = attributes.MICRO
            )
        ]
        
class Foo(ItemWithAutoLastUpdatedStampMixin, item.Item):
    typeName = 'Foo'
    
    title = attributes.text()
    dob = attributes.timestamp()
    lastUpdated = MyAxiomLastUpdatedAttribute(default=Time())
    
    def __repr__(self):
        return '<Foo title="%s" lastUpdated="%s" schemaVersion="%d" />' % (self.title, self.lastUpdated, self.schemaVersion)

if __name__ == "__main__":
    import time
    s = store.Store(debug=False)
    Foo(store=s, title=u"Foo:Bar")
    
    print "BEFORE: ", s.findFirst(Foo)
    print "SLEEPING..."
    time.sleep(5)
    
    i = s.findFirst(Foo)
    i.title = u"F O O  :  B A R !"
    
#    The lastUpdated value has been updated in SQLite, but Axiom won't know
#    about it until you uncache the affected record.
#    I suppose that unless there is a way for sqlite to alert axiom of underlying changes
#    this sqltrigger method is not very practical. In this respect it may be related 
#    to ticket:450
    s.objectCache.uncache(i.storeID, i)
    
    print "AFTER: ", s.findFirst(Foo)