Ynt: WAL and backup recovery

Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote in message
news:14951(dot)990634138(at)sss(dot)pgh(dot)pa(dot)us(dot)(dot)(dot)
> Dario Brignardello <dbrignar(at)sinectis(dot)com> writes:
> > checkpoint_segments = 1
> > checkpoint_timeout = 30
>
> Reducing checkpoint_segments and checkpoint_timeout is actually
> seriously counterproductive, if your problem is amount of disk space
> chewed up by WAL logs during a long transaction (such as bulk load of
> a big table). The WAL log cannot be truncated until the xact commits,
> so the checkpoints that happen meanwhile just cause log bloat. Lots
> of it, because each checkpoint causes fresh copying of modified pages
> into the WAL log.
So let me know one thing, does checkpoint cause copying modified pages to
WAL log or does it just flush the modified pages to disk?
I thought WAL writings occur when pages being modified, deleted or inserted,
please correct me if I am wrong...thanx....

Murat

>
> Try increasing those numbers, not decreasing them. Maybe 10/600 or so?
>
> Also, if you are short on disk space for WAL, increasing wal_files isn't
> such a great idea either.
>
> regards, tom lane
>
> ---------------------------(end of broadcast)---------------------------
> TIP 2: you can get off all lists at once with the unregister command
> (send "unregister YourEmailAddressHere" to majordomo(at)postgresql(dot)org)