Re: Torn page hazard in ginRedoUpdateMetapage()

On Thu, May 3, 2012 at 12:16 AM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> Having said all that, I wasn't really arguing that this was a guaranteed
> safe thing for us to rely on; just pointing out that it's quite likely
> that the issue hasn't been seen in the field because of this type of
> consideration.

Well, we do rely, in numerous places, on writes << 512 bytes not
getting torn.  pd_prune_xid, index tuple kills, heap tuple hint bits,
relmapper files, etc.  We generally assume, for example, that a 4-byte
write which is 4-byte aligned does not need to be WAL-logged, which
would be necessary if we thought that the write might be torn.

Are you planning to commit Noah's patch?

-- 
Robert Haas
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