Re: Block-level CRC checks

Jonah H. Harris wrote:
> PG doesn't care because during hint-bits aren't logged and during
> normal WAL replay, the old page will be pulled from the WAL.  I
> believe what Tom is referring to is that the buffer PG sends to
> write() can still be modified by way of SetHintBits between the time
> smgrwrite is called and the time the actual write takes place, which
> is why we can't rely on a checksum of the buffer pointer passed to
> smgrwrite and friends.
> 
> If we're double-buffering the write, I don't see where we could be
> introducing a torn-page, as we'd actually be writing a copied version
> of the buffer.  Will look into this.

The torn page is during kernel write to disk, I assume, so it is still
possible.

--  Bruce Momjian  <bruce@momjian.us>        http://momjian.us EnterpriseDB
http://enterprisedb.com
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