Re: pg_checksums (or checksums in general) vs tableam

Hi,

On July 10, 2019 9:12:18 AM PDT, Magnus Hagander <magnus(at)hagander(dot)net> wrote:
>On Wed, Jul 10, 2019 at 3:05 PM Michael Paquier <michael(at)paquier(dot)xyz>
>wrote:
>
>> On Wed, Jul 10, 2019 at 11:42:34AM +0200, Magnus Hagander wrote:
>> > pg_checksums enumerate the files. What if there are files there
>from a
>> > different tableam? Isn't pg_checksums just going to badly fail
>then,
>> since
>> > it assumes everything is heap?
>> >
>> > Also, do we allow AMs that don't support checksumming data? Do we
>have
>> any
>> > checks for tables created with such AMs in a system that has
>checksums
>> > enabled?
>>
>> Table AMs going through shared buffers and smgr.c, like zedstore,
>> share the same page header, meaning that the on-disk file is the same
>> as heap, and that checksums are compiled similarly to heap.
>> pg_checksums is not going to complain on those ones and would work
>> just fine.
>
>
>> Table AMs using their own storage layer (which would most likely use
>> their own checksum method normally?) would be ignored by pg_checksums
>> if the file names don't match what smgr uses, but it could result in
>> failures if they use on-disk file names which match.
>>
>
>That would be fine, if we actually knew. Should we (or have we
>already?)
>defined a rule that they are not allowed to use the same naming
>standard
>unless they have the same type of header?

No, don't think we have already. There's the related problem of what to include in base backups, too.

Andres
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