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.
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