Re: Block-level CRC checks

Aidan Van Dyk <aidan@highrise.ca> writes:

> * Greg Stark <greg.stark@enterprisedb.com> [081117 03:54]:
>> [sorry for top-posting - damn phone]
>>
>> I thought of saying that too but it doesn't really solve the problem.  
>> Think of what happens if someone sets a hint bit on a dirty page.
>
> If the page is dirty from a "real change", then it has a WAL backup block
> record already, so the torn-page on disk is going to be fixed with the wal
> replay ... *because* of the torn-page problem already being "solved" in PG.
> You don't get the hint-bits back, but that's no different from the current
> state.  But nobody's previously cared if hint-bits wern't set on WAL replay.

Hum. Actually I think you're right.

However you still have a problem that someone could come along and set the
hint bit between calculating the CRC and actually calling write.



--  Gregory Stark EnterpriseDB          http://www.enterprisedb.com Ask me about EnterpriseDB's 24x7 Postgres support!