Re: Enabling Checksums

On Tue, 2013-04-23 at 01:08 +0300, Ants Aasma wrote:
> A slight delay, but here it is. I didn't lift the checksum part into a
> separate file as I didn't have a great idea what I would call it. The
> code is reasonably compact so I don't see a great need for this right
> now. It would be more worth the effort when/if we add non-generic
> variants. I'm not particularly attached to the method I used to mask
> out pd_checksum field, this could be improved if someone has a better
> idea how to structure the code.

Thank you. A few initial comments:

I have attached (for illustration purposes only) a patch on top of yours
that divides the responsibilities a little more cleanly.

* easier to move into a separate file, and use your recommended compiler
flags without affecting other routines in bufpage.c
* makes the checksum algorithm itself simpler
* leaves the data-page-specific aspects (mixing in the page number,
ignoring pd_checksum, reducing to 16 bits) to PageCalcChecksum16
* overall easier to review and understand

I'm not sure what we should call the separate file or where we should
put it, though. How about src/backend/utils/checksum/checksum_fnv.c? Is
there a clean way to override the compiler flags for a single file so we
don't need to put it in its own directory?

Regards,
    Jeff Davis