From: | Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us> |
---|---|
To: | Vadim Mikheev <vmikheev(at)reveredata(dot)com> |
Cc: | Hiroshi Inoue <Inoue(at)tpf(dot)co(dot)jp>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Manfred Koizar <mkoi-pg(at)aon(dot)at>, pgsql-hackers(at)postgresql(dot)org |
Subject: | Re: Nested transactions: low level stuff |
Date: | 2003-03-21 15:18:16 |
Message-ID: | 200303211518.h2LFIG926809@candle.pha.pa.us |
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Lists: | pgsql-hackers |
Vadim Mikheev wrote:
> > If there was no official vote, the conclusion came from the discussion
> > that almost everyone wanted subtransactions without UNDO.
> >
> > I don't want to rehash it. If you want a vote, let's vote.
> >
> > Who wants subtransactions with UNDO and who wants it with a separate
> > transaction id for every subtransaction?
>
> Don't mess up things, Bruce - UNDO is not for subtransactions only!
> UNDO would allow immediate storage cleanup and vacuum would
> not be required anymore. Subtransactions/savepoints would be just
> "by-effect" of UNDO. (And, btw, how would you implement "implicit"
> savepoints with "separate subtrans id" approach?)
>
> But do we need any voting, actually? Is there anybody who want/ready
> implement UNDO functionality? No? Then there is nothing to vote about.
> (Though I personally consider "subtrans id-s" as "messing up messy
> transaction system". Messing up is always easier then re-designing).
Yes, Vadim is right. The UNDO was much more than subtransactions, but
actually a discussion comparing UNDO and the free-space map approach.
It would help with subtransactions, but it is only tangentially related.
I think the issue was:
Do we want UNDO or FSM?
We chose FSM but UNDO is still an option.
Do we want UNDO just for subtransactions?
That was pretty easily defeated, though I made an argument that you
could do UNDO pretty cheaply when you have WAL ensuring crash recovery.
--
Bruce Momjian | http://candle.pha.pa.us
pgman(at)candle(dot)pha(dot)pa(dot)us | (610) 359-1001
+ If your life is a hard drive, | 13 Roberts Road
+ Christ can be your backup. | Newtown Square, Pennsylvania 19073
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