-------------- Original message ---------------------- From: Garry Saddington <garry@xxxxxxxxxxxxxxxxxxxx> > On Thursday 19 June 2008 16:55, Joshua D. Drake wrote: > > On Thu, 2008-06-19 at 16:55 +0100, Garry Saddington wrote: > > > I have had a serious loss of data and wondered if anyone could shed any > > > light on what may have happened. > > > My users have been writing reports on students. No error messages have > > > been produced and when called back up the reports seem to be present at > > > the time of writing. However, next day they have disappeared, and they do > > > not appear in a pg_dump. They seem to have been kept in memory and never > > > written to disk. > > > We are using Zope and connecting to Postgres through psycopg on Centos 5. > > > I suspect a hard disk failure but any other ideas would be welcome. > > > Would these reports be in the WAL? > > > > If it was hardware related you would know, quickly. This sounds a great > > deal more like an application level interaction. Perhaps your zope > > application caches things for a while before committing to disk? > Yes I thought of this but once the report is sent to the DB a separate query > is run to get all of that teacher's reports and these are then displayed on a > new page. They all appear here but then disappear later. Zope has transaction > machinery that rolls everything back on an error, so Postgres must have > indicated a successful write somehow. I read in a Postgres manual that the > hard disk may report to the OS that a write has occured when it actually has > not, is this possible? Oh, and the problem has been intermittant. Another > thing that happened this morning is that Postgres had today as 18/06/2008 > when in fact it was 19/06/2008 and the OS reported this correctly. Restarting > postgres sorted it, could this be the problem? > Regards > Garry > Seems like a transaction with no commit. Basically along as the session is active the data is there but once the session is closed the data does not persist. -- Adrian Klaver aklaver@xxxxxxxxxxx
