[SQLObject] Transaction Implementation v2

[Luke O. <lu...@me...>]

Hello all -

Wow. Following Ian's suggestions yesterday, I was able to trim all of
this transaction support down to a one-line addition to SQLObject,
plus the now-combined MemoryTransaction class.

New interface:

m = MemoryTransaction()
a = Person.new(connection=m, ...)
b = Person(2).copyToConnection(m)
m.commit()

Changes to SQLObject necessary:

Same changes as before (in new() and joins), but __new__ no longer
needs useCache argument.

New method:

    def copyToConnection(self, conn):
        return self.__class__(self.id, connection=conn)

That's it. :)

Cache.py:

Cache.clear() does not behave as I would expect, still leaving
weakrefs around. It's not used at all within SQLObject that I can
find, so I'm assuming I'm safe to change the behavior to be an
overall purge:

    def clear(self):
        self.lock.acquire()
-       for key, value in self.cache.items():
-           self.expiredCache[key] = ref(value)
+       self.expiredCache = {}
        self.cache = {}
        self.lock.release()

(Otherwise my MemoryTransaction cache gets a ref to the new persisted
objects with the wrong connections inside them... could fix this by
making a no-op cache for Memory Transaction, but I have a feeling
this is the expected behavior for Cache.clear())


New version at http://www.amoebagod.com/SQLObject-T2.zip

- Luke