Re: Block at a time ...

Greg - with Oracle, I always do fixed 2GB dbf's for poartability, and
preallocate the whole file in advance. However, the situation is a bit
different in that Oracle will put blocks from multiple tables and indexes in
a DBF if you don't tell it differently.

Tom - I'm not sure what Oracle does, but it literally writes the whole
extent before using it .... I think they are just doing the literal
equivalent of *dd if=/dev/zero* ... it takes several seconds to prep a 2GB
file on decent storage.

Cheers
Dave

On Wed, Mar 17, 2010 at 9:27 AM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:

> Greg Stark <gsstark(at)mit(dot)edu> writes:
> > I think we need posix_fallocate().
>
> The problem with posix_fallocate (other than questionable portability)
> is that it doesn't appear to guarantee anything at all about what is in
> the space it allocates. Worst case, we might find valid-looking
> Postgres data there (eg, because a block was recycled from some recently
> dropped table). If we have to write something anyway to zero the space,
> what's the point?
>
> regards, tom lane
>