James Henstridge wrote at 2008-1-21 23:40 +0900:
> ...
>= DB-API Two-Phase Commit =
>
>Many databases have support for two-phase commit. Adapters for some
>of these databases expose this support, but often through mutually
>incompatible extensions to the DB-API standard.
>
>Standardising the API for two-phase commit would make it easier for
>applications and libraries to support two-phase commit with multiple
>databases.
>
>
>== Connection Methods ==
>
>A database adapter that supports two phase commit (2PC) shall provide
>the following additional methods on its connection object:
>
> .xa_begin(xid)
>
> Begins a 2PC transaction with the given ID. This method
> should be called outside of a transaction (i.e. nothing may
> have executed since the last .commit() or .rollback()).
>
> Furthermore, it is an error to call .commit() or .rollback()
> within the 2PC transaction (what error?).
>
> If the database does not support 2PC, a NotSupportedError will
> be raised.
>
> .xa_prepare()
>
> Performs the first phase of a transaction started with
> xa_begin(). It is an error to call this method outside of a
> 2PC transaction.
>
> After calling xa_prepare(), no statements can be executed
> until xa_commit() or xa_rollback() have been called.
>
> .xa_commit(xid=None, onephase=False)
>
> When called with no arguments, xa_commit() commits a 2PC
> transaction previously prepared with xa_prepare().
>
> When called as xa_commit(onephase=True), it may be used to
> commit the transaction prior to calling xa_prepare(). This
> may occur if only a single resource ends up participating in
> the global transaction.
>
> When called as xa_commit(xid), it commits the given
> transaction. If an invalid transaction ID is provided, a
> DatabaseError will be raised. This form should be called
> outside of a transaction, and is intended for use in recovery.
>
> On return, the 2PC transaction is ended.
>
> .xa_rollback(xid=None)
>
> When called with no arguments, xa_rollback() rolls back a 2PC
> transaction. It may be called before or after xa_prepare().
>
> When called as xa_commit(xid), it rolls back the given
> transaction. If an invalid transaction ID is provided, a
> DatabaseError will be raised. This form should be called
> outside of a transaction, and is intended for use in recovery.
>
> On return, the 2PC transaction is ended.
>
> .xa_recover()
>
> Returns a list of pending transaction IDs suitable for use
> with xa_commit(xid) or xa_rollback(xid).
>
> If the database does not support transaction recovery, it may
> return an empty list or NotSupportedError.
I would prefer, if
* "xa_begin" would be optional
the current DB API performs automatic "begin" when there is a
need for it.
* the transaction id be chosen automatically, optinally guided
by "Connection" configuration (to obtain "readable" transaction ids)
* the use of "prepare_transaction" triggers a two phase commit --
otherwise a one phase commit is used.
--
Dieter
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