Обсуждение: nested transactions

Hi,

I am aware that at least 7.1 did not support nested transactions and
it's my impression that 7.2 doesn't either.  Am I correct about this?
Also, are nexted transactions "on the board," and if so, when/what
release are they planned for?

Thanks in advance...

--------------------------------------------------------------
Steven D. Arnold                                    Neosynapse
stevena@neosynapse.net                        Managing Partner
AIM: abraxan                       MSN: neosynapse@hotmail.com

On Mon, 22 Apr 2002 17:01:27 -0400
"Steven D. Arnold" <stevena@neosynapse.net> wrote:
> Hi,
>
> I am aware that at least 7.1 did not support nested transactions and
> it's my impression that 7.2 doesn't either.  Am I correct about this?

Yes.

> Also, are nexted transactions "on the board," and if so, when/what
> release are they planned for?

They're on the TODO list, but AFAIK no one has volunteered to implement
them yet.

Cheers,

Neil

--
Neil Conway <neilconway@rogers.com>
PGP Key ID: DB3C29FC

Neil Conway <nconway@klamath.dyndns.org> writes:
> "Steven D. Arnold" <stevena@neosynapse.net> wrote:
>> Also, are nexted transactions "on the board," and if so, when/what
>> release are they planned for?

> They're on the TODO list, but AFAIK no one has volunteered to implement
> them yet.

Steven should probably be warned that this is a "don't hold your breath"
kind of thing.  AFAICS, nested transactions would require a huge amount
of work by very knowledgeable hackers (for example, looking at nearly
every error-exit condition in the backend, to see if it's going to cause
a problem with continuing the current transaction).  The small number
of people who could do it have other priorities.

            regards, tom lane

From my SQL Server days, I remember the nested transactions feature being one that I spent a lot of time trying to
undo. As I recall, if you had a trigger that called a function (stored procedure) and the SP threw an error, the
triggerwould merrily go about its business as if nothing had happened.  You had to encircle each sql statement with
errortrapping code, and if one was found, see how far into the nest of transactions you were, and roll back the
transaction(if you were in one) then set the return code to let all the higher level transactions know something went
wrong,so each of them could decide whether to roll back. 

If the error checking was in the DBMS (instead of having to be written by hand) and the nested transactions rolled each
otherback if an error was detected, wouldn't  we be back where we are now? 

What's the benefit?

- Ian

>>> Tom Lane <tgl@sss.pgh.pa.us> 04/22/02 03:11PM >>>
Neil Conway <nconway@klamath.dyndns.org> writes:
> "Steven D. Arnold" <stevena@neosynapse.net> wrote:
>> Also, are nexted transactions "on the board," and if so, when/what
>> release are they planned for?

> They're on the TODO list, but AFAIK no one has volunteered to implement
> them yet.

Steven should probably be warned that this is a "don't hold your breath"
kind of thing.  AFAICS, nested transactions would require a huge amount
of work by very knowledgeable hackers (for example, looking at nearly
every error-exit condition in the backend, to see if it's going to cause
a problem with continuing the current transaction).  The small number
of people who could do it have other priorities.

            regards, tom lane

---------------------------(end of broadcast)---------------------------
TIP 2: you can get off all lists at once with the unregister command
    (send "unregister YourEmailAddressHere" to majordomo@postgresql.org)

Neil Conway wrote:
> On Mon, 22 Apr 2002 17:01:27 -0400 "Steven D. Arnold"
> <stevena@neosynapse.net> wrote:
> > Hi,
> >
> > I am aware that at least 7.1 did not support nested transactions and
> > it's my impression that 7.2 doesn't either.  Am I correct about this?
>
> Yes.
>
> > Also, are nexted transactions "on the board," and if so, when/what
> > release are they planned for?
>
> They're on the TODO list, but AFAIK no one has volunteered to
> implement them yet.

See the 'transactions' link from the TODO page for more detailed
implementation issues.

--
  Bruce Momjian                        |  http://candle.pha.pa.us
  pgman@candle.pha.pa.us               |  (610) 853-3000
  +  If your life is a hard drive,     |  830 Blythe Avenue
  +  Christ can be your backup.        |  Drexel Hill, Pennsylvania 19026