Re: zero_damaged_pages doesn't work

On 9/27/2010 4:40 PM, Jeff Davis wrote:
> It does zero the page in the buffer, but I don't think it marks it as
> dirty. So, it never really makes it to disk as all-zeros.

Ah ha ! This is certainly consistent with the observed behavior.

> zero_damaged_pages is not meant as a recovery tool. It's meant to allow
> you to pg_dump whatever data is not damaged, so that you can restore
> into a fresh location.

It'd be useful for future generations if this were included in the doc.

The latest version :
http://www.postgresql.org/docs/9.0/static/runtime-config-developer.html
still talks about destroying data (which at least to me implies a
persistent change
to the on-disk bits) and fails to mention that the zeroing only occurs
in the
page pool sans write-back.

If it helps, I'd be happy to contribute some time to fix up the docs,
but imho a simple
copy/paste of your text above would be sufficient.