Re: Range Types - typo + NULL string constructor - Mailing list pgsql-hackers

From Jeff Davis
Subject Re: Range Types - typo + NULL string constructor
Date
Msg-id 1319647625.15846.1.camel@jdavis
Whole thread Raw
In response to Re: Range Types - typo + NULL string constructor  (Robert Haas <robertmhaas@gmail.com>)
List pgsql-hackers
On Wed, 2011-10-26 at 12:19 -0400, Robert Haas wrote:
> > 1. In session A: BEGIN; SELECT * FROM foo WHERE id = 1; COMMIT;
> >   The row has xmin = 123456, and it is cached as committed in the one-item
> > cache by TransactionLogFetch.
> > 2. A lot of time passes. Everything is frozen, and XID wrap-around happens.
> > (Session A is idle but not in a transaction, so it doesn't inhibit
> > freezing.)
> > 3. In session B: BEGIN: INSERT INTO foo (id) VALUES (2); ROLLBACK;
> >   By coincidence, this transaction was assigned XID 123456.
> > 4. In session A: SELECT * FROM foo WHERE id = 2;
> >   The one-item cache still says that 123456 committed, so we return the
> > tuple inserted by the aborted transaction. Oops.

Yes, that's the scenario I was talking about.

> Oh, hmm.  That sucks.

It didn't seem like a major concern a while ago:
http://archives.postgresql.org/message-id/28107.1291264452@sss.pgh.pa.us

Regards,Jeff Davis



pgsql-hackers by date:

Previous
From: Magnus Hagander
Date:
Subject: Re: pgsql_fdw, FDW for PostgreSQL server
Next
From: Simon Riggs
Date:
Subject: Re: Hot Backup with rsync fails at pg_clog if under load