Tom,

"Putting in "dozens of hours" is not the issue here --- the problem is
that there isn't any solution in sight, and I'm not eager to go down a
path that has an obvious dead end."

Well, I doubt we're breaking any new ground with this discussion.  If I really 
cared about this feature, I would get in touch with CJ Date and see what he 
has to say about it; but I don't care that much, except from a "Postgres 
marketability" perspective.

Perhaps the people on this list who are pushing 2PC could do the ground work?  
I'd suggest starting with the collected works of CJ Date and Hugh Darwin, and 
contacting them if it's not already in a book.

-- 
-Josh Berkus
 Aglio Database Solutions
 San Francisco


Mon, 23 Jun 2003 14:14:31 -0700
Josh Berkus <josh@agliodbs.com>
Re: Two Phase Commit WAS: Re: Two weeks to feature freeze
> Perhaps the people on this list who are pushing 2PC could do the ground work?  


- 2PC is better than a standard transaction when dealing with multiple
servers as it can recover in some circumstances (but not all).

- 2PC (XA support as described by the X/Open group) is the only
implementation of distributed transactions supported by many third party
components -- that I'm aware of -- to the point where it is a part of
the Java Spec on dealing with distributed transactions.

- 2PC isn't very good in a number of circumstances, as such PostgreSQL
should avoid its use when PostgreSQL has a choice in the matter -- like
communication with other PostgreSQL servers.

This is a case of learning to speak Japanese because all of the people
you want to talk with only speak Japanese. It simply doesn't matter how
good Esperanto is.

-- 
Rod Taylor <rbt@rbt.ca>

PGP Key: http://www.rbt.ca/rbtpub.asc
23 Jun 2003 18:05:17 -0400
Rod Taylor <rbt@rbt.ca>
Re: Two Phase Commit WAS: Re: Two weeks to feature freeze
Rod Taylor wrote:

>>Perhaps the people on this list who are pushing 2PC could do the ground work?  
> 
> - 2PC is better than a standard transaction when dealing with multiple
> servers as it can recover in some circumstances (but not all).
> 
> - 2PC (XA support as described by the X/Open group) is the only
> implementation of distributed transactions supported by many third party
> components -- that I'm aware of -- to the point where it is a part of
> the Java Spec on dealing with distributed transactions.
> 
> - 2PC isn't very good in a number of circumstances, as such PostgreSQL
> should avoid its use when PostgreSQL has a choice in the matter -- like
> communication with other PostgreSQL servers.
> 
> This is a case of learning to speak Japanese because all of the people
> you want to talk with only speak Japanese. It simply doesn't matter how
> good Esperanto is.

I don't think it could have been said any better. There are a host of
improvements on the standard 2PC protocol, including 3PC, multi-cast
2PC, and other variants both synchronous and asynchronous. But if
PostgreSQL is going to work with XA, then it doesn't get to choose the
TM or the protocol. The only relevance of this thread, as I see it, is
whether or not core will stomach an XA-compatible 2PC implementation
in the backend. If not, then is Satoshi Nagayasu in vain? That was
what I "sensed" in the original thread 6 months ago, that the 2PC work
being done by Satoshi Nagayasu was going to be allowed to die on the vine.

Mike Mascari
mascarm@mascari.com




Mon, 23 Jun 2003 18:22:09 -0400
Mike Mascari <mascarm@mascari.com>
Re: Two Phase Commit WAS: Re: Two weeks to feature freeze
Rod Taylor wrote:
-- Start of PGP signed section.
> > Perhaps the people on this list who are pushing 2PC could do the ground work?  
> 
> 
> - 2PC is better than a standard transaction when dealing with multiple
> servers as it can recover in some circumstances (but not all).
> 
> - 2PC (XA support as described by the X/Open group) is the only
> implementation of distributed transactions supported by many third party
> components -- that I'm aware of -- to the point where it is a part of
> the Java Spec on dealing with distributed transactions.
> 
> - 2PC isn't very good in a number of circumstances, as such PostgreSQL
> should avoid its use when PostgreSQL has a choice in the matter -- like
> communication with other PostgreSQL servers.
> 
> This is a case of learning to speak Japanese because all of the people
> you want to talk with only speak Japanese. It simply doesn't matter how
> good Esperanto is.

Agreed --- other db's have it, and people ask for it, so we should just
do our best and document the limitations.

-- 
  Bruce Momjian                        |  http://candle.pha.pa.us
  pgman@candle.pha.pa.us               |  (610) 359-1001
  +  If your life is a hard drive,     |  13 Roberts Road
  +  Christ can be your backup.        |  Newtown Square, Pennsylvania 19073

Mon, 23 Jun 2003 18:23:03 -0400 (EDT)
Bruce Momjian <pgman@candle.pha.pa.us>
Re: Two Phase Commit WAS: Re: Two weeks to feature freeze
> I don't think it could have been said any better. There are a host of
> improvements on the standard 2PC protocol, including 3PC, multi-cast
> 2PC, and other variants both synchronous and asynchronous. But if
> PostgreSQL is going to work with XA, then it doesn't get to choose the
> TM or the protocol. The only relevance of this thread, as I see it, is

I'm no expert in this area, but XA seems to be the choice for Java based
Transaction Servers, so at very least the JDBC guys will want to have
the ability to fake XA.

> whether or not core will stomach an XA-compatible 2PC implementation
> in the backend. If not, then is Satoshi Nagayasu in vain? That was

No, it's not in vain to add 2PC (XA-compatible was his interest at the
time) into the backend.

What is debatable is whether the PostgreSQL folks will implement a
replication system based on it.

> what I "sensed" in the original thread 6 months ago, that the 2PC work
> being done by Satoshi Nagayasu was going to be allowed to die on the vine.

It is difficult work, but is no less useful than nested transactions
will be. A certain segment of the user-base will be jumping up and down
when they get them, myself included.

-- 
Rod Taylor <rbt@rbt.ca>

PGP Key: http://www.rbt.ca/rbtpub.asc
23 Jun 2003 18:32:18 -0400
Rod Taylor <rbt@rbt.ca>
Re: Two Phase Commit WAS: Re: Two weeks to feature freeze