Hi Tim,

I have two suggestions, I hope one of them helps.

1) Attached is a TM.py file that I wrote based on the one you mention 
below.  I've tried to make it more obvious and better documented.

2) Don't use this kind of functionality, but rather use sub-transaction 
commits.

The first suggestion has more overhead than what I assume you would 
need, but the second one won't work for all situations.

A Fishbowl proposal of mine, HashingSupport, was going to use the same 
kind of hook you are asking about.  In this case though, using 
sub-transaction commits made a lot more sense.

In general though, I think that _v_* attributes pose a non-trivial 
problem that probably requires a hook on abort() if not commit() as well.

John

Tim McLaughlin wrote:

> Is there a hook for before the transaction is committed for objects which
> subclass Persistent?  I found __inform_commit__ for a "registered" object,
> but I can't seem to get that to work as I thought it did.  I also tried
> subclassing TM like a DA, but to no avail.
> 
> TIA,
> Tim
> 
> ___________________________________________________________
> Tim McLaughlin                                BCSwebservices.net
> Director, Technical Group             1950 Old Gallows Road
> tel:  (703) 790.8081 x111             Suite 201
> [EMAIL PROTECTED]                Vienna, VA 22182
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> 
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w w w . d a t a c h a n n e l . c o m
##############################################################################
# 
# Zope Public License (ZPL) Version 1.0
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##############################################################################
"""Provide support for linking an external transaction manager with Zope's
"""


class TM:
    """Mix-in class that provides transaction management support

    A sub class should call self._register() whenever it performs
    any transaction-dependent operations (e.g. sql statements).

    The sub class will need to override:
      _begin if necessary
      _vote to raise an except if necessary
      _finish to finallize work,
      _abort to roll-back work
    """

    def _begin(self):
        """Hook method to begin external transaction.
        This may be called multiple times,"""
        pass

    def _vote(self):
        """Hook method to vote on success of transaction commit.
        This will only be called once,"""
        pass

    def _finish(self):
        """Hook method to complete transaction work.
        This may be called multiple times."""
        pass

    def _abort(self):
        """Hook method to undo transaction work.
        This may be called multiple times."""
        pass

    _registered=None

    class Surrogate:
        "A ZODB persistent look-alike."
        def __init__(self, connection):
            self._p_jar=connection

    def _register(self):
        """This method will register a surrogate persistent
        object with the transaction.  This surrogate will include
        me in the tpc_* two-phase commit process."""

        if not self._registered:
            try:
                get_transaction().register(TM.Surrogate(self))
                self._registered=1
            except:
                import traceback
                traceback.print_exc()
                pass

    def commit(self, *ignored):
        "We don't need to actually do an storing."
        pass

    def tpc_begin(self, *ignored):
        "Connection method to begin a commit."
        self._begin()

    def tpc_vote(self, *ignored):
        "Connection method to vote on commit success."
        self._vote()
        
    def tpc_finish(self, *ignored):
        """Connection method to signal commit success.
        This should *never* fail"""
        try: self._finish()
        finally: self._registered=0

    def abort(self, *ignored):
        """Connnection method to signal commit failure.
        This should *never* fail"""
        try: self._abort()
        finally: self._registered=0

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