Re: AW: Plans for solving the VACUUM problem

Barry Lind wrote:
>
>
> Zeugswetter Andreas SB wrote:
>
> >>> Vadim, can you remind me what UNDO is used for?
> >>
> >> 4. Split pg_log into small files with ability to remove old ones (which
> >> do not hold statuses for any running transactions).
> >
> >
> > They are already small (16Mb). Or do you mean even smaller ?
> > This imposes one huge risk, that is already a pain in other db's. You need
> > all logs of one transaction online. For a GigaByte transaction like a bulk
> > insert this can be very inconvenient.
> > Imho there should be some limit where you can choose whether you want
> > to continue without the feature (no savepoint) or are automatically aborted.
> >
> > In any case, imho some thought should be put into this :-)
> >
> > Another case where this is a problem is a client that starts a tx, does one little
> > insert or update on his private table, and then sits and waits for a day.
> >
> > Both cases currently impose no problem whatsoever.
>
> Correct me if I am wrong, but both cases do present a problem currently
> in 7.1. The WAL log will not remove any WAL files for transactions that
> are still open (even after a checkpoint occurs). Thus if you do a bulk
> insert of gigabyte size you will require a gigabyte sized WAL
> directory. Also if you have a simple OLTP transaction that the user
> started and walked away from for his one week vacation, then no WAL log
> files can be deleted until that user returns from his vacation and ends
> his transaction.

As a rule of thumb, online applications that hold open
transactions during user interaction are considered to be
Broken By Design (tm). So I'd slap the programmer/design
team with - let's use the server box since it doesn't contain
anything useful.

Jan

--

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