[Z3-sqlos] RFC: Transaction simplification branch

[Brian Sutherland]

Hi,

I just cut a new branch with some major simplifications to the
transaction machinery of sqlos. But these are _big_, so I would like to
ask for testing/comments before I go further.

Perhaps I went too far? Or cut something necessary?

The branch is at:
http://codespeak.net/svn/z3/sqlos/branch/jinty-simplify-transactions

The main changes are:

* Call sync as a pre-commit hook.
    (kudos to Jim, http://www.zope.org/Collectors/Zope3-dev/511)

* don't syncUpdate anymore on commit or sync on prepare
  (It was already done in the pre-commit)

* Don't force the zope.app.rdb data manager to join the transaction.
  (Thanks to the pre-commit hook this is not necessary)

* Rip out the testing support code in the transaction module and re-write
  the unit test in a weaker but less brittle way. We test results now,
  not process.

* Make self.objects self._objects.

* Rip out sanity checking code checking that the transaction manager
  always dealt with the same transaction.

* The Transaction Manager doesn't take the sqlconnection as an argument
  anymore as that has become un-necessary with the other changes.

* Get rid of the events module.
    - The modified subscriber disappeared as we don't call it anymore.
    - The expired event was hardwired into _transaction.py

    Rationale: When you are committing/aborting a transaction you don't
    really want to be firing events. This makes it very easy for people
    to hook in exception raising code which can make a serious mess of
    things...

    Also it was just too many layers of confusion for what was needed.

--
Brian Sutherland

Metropolis - "it's the first movie with a robot. And she's a woman.
              And she's EVIL!!"