On Fri, 2004-04-30 at 01:02, Bruce Momjian wrote:
Simon Riggs wrote:
On Sun, 2004-04-25 at 19:06, Alvaro Herrera wrote:
Hackers,

This patch adds subtransaction support into the storage manager. Files
created or dropped inside a subtransaction are correctly dealt with at
subtransaction commit or abort.
- pg_clog/pg_subtrans. Need a solution.


PS: somehow I managed to get tired of the phrase "nested transactions"
and I'm using the term "subtransactions" instead. In my head they are
the same thing ...
Impressive.

As you're aware, our current work overlaps.
pg_clog doesn't seem like the place to record subtransactions, though
maybe it is... could we not give subtransactions a txnid just as with
flat transactions? That way we can record everything in pg_clog AND
recovery will work without further modification - as long as the failure
of a top level transaction causes failure of every subtransaction EVEN
if the subtrans originally committed.
The problem is we have to atomically mark multiple transactions as
committed/aborted in pg_clog. Each subtransaction does get its own xid,
it is just that pg_subtrans maps each xid to is parent xid for use in
atomically marking the xids as committed/aborted.

Recovery via xlog should be fine.
Phewww!
If you add pg_subtrans, you will need to make recovery work all over
again...really, you don't want to be doing that, do you?

I also have other questions....
Forgive my lack of attention: I want SAVEPOINTs, not subtransactions...
how do we do those?
Savepoints are basically just a BEGIN at the save point, and a ROLLBACK
to get you back to the saved spot. It is just window-dressing on top of
nested transactions.
OK, but is anybody working on the window dressing bit, so that we have
ANSI compliant commands?

Best Regards, Simon

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