Re: Block-level CRC checks

Bruce Momjian wrote:
> Tom Lane wrote:
>>
>> The suggestions that were made upthread about moving the hint bits
>> could resolve the second objection, but once you do that you might
>> as well just exclude them from the CRC and eliminate the guessing.
> 
> OK, crazy idea #3.  What if we had a per-page counter of the number of
> hint bits set --- that way, we would only consider a CRC check failure
> to be corruption if the count matched the hint bit count on the page.

Can I piggy-back on Bruce's crazy idea and ask a stupid question?

Why are we writing out the hint bits to disk anyway? Is it really so
slow to calculate them on read + cache them that it's worth all this
trouble? Are they not also to blame for the "write my import data twice"
feature?

--  Richard Huxton Archonet Ltd