Re: Gotchas about pg_verify_checksums

> On 11 Apr 2018, at 01:53, Michael Paquier <michael@paquier.xyz> wrote:
>
> On Tue, Apr 10, 2018 at 10:27:19PM +0200, Daniel Gustafsson wrote:
>>> On 10 Apr 2018, at 06:21, Michael Paquier <michael@paquier.xyz> wrote:
>> Does it really imply that?  Either way, the tool could potentially be useful
>> for debugging a broken cluster so I’m not sure that stating it requires a
>> cleanly shut down server is useful.
>
> Torn pages could lead to false positives.  So I think that the tool's
> assumptions are right.

Right, I misunderstood your initial email but I see what you mean.  Yes, you
are right and with that +1 on your patch.

> I am wondering as well if we should not actually rename the tool?  Why
> not naming it pg_checksums instead of pg_verify_checksums, and add an
> --action switch to it which can be used to work on checksums.  The
> obvious option to support in v11 is a "verify" mode, but I would imagine
> that a "disable" and "enable" modes would be useful as well, and all the
> APIs are here already to be able to do an in-place update of the
> checksums, and then switch the control file properly.  We have no idea
> at this stage if a patch to enable checksums while the cluster is online
> will be able to make it, still a way to switch checksums while the
> cluster is offline is both reliable and easy to implement.  Not saying
> do to that for v11 of course, I would like to keep the door open for
> v12.

Naming it pg_checksums, with only verification as an option, seems to me to
imply future direction for 12 more than what pg_verify_checksums does.  I would
leave it the way it is, but I don’t have very strong opinions (or any plans on
hacking on offline checksum enabling for that matter).

cheers ./daniel