Re: "clearing" a relation file !

"Michel SALAIS" <msalais@msym.fr> writes:
> \! dd if=/dev/zero of=$file_path bs=1024 count=100

This is fairly useless.

As you already noticed, it corrupts the on-disk data but has no
immediate effect on what's in shared buffers.  Depending on what
the timing of checkpoints is, the damage might even be self-healed
due to writing out shared buffers after you corrupt the storage.

The other problem with this specific test is that an all-zero
page is considered to be a valid state.  You may consider that
a problem or not, but we're quite unlikely to change it, because
doing so would create false failure reports.  See the mechanisms
around file extension.

            regards, tom lane