Re: preserving db/ts/relfilenode OIDs across pg_upgrade (was Re: storing an explicit nonce)

On Tue, Dec 14, 2021 at 2:35 AM Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
>
> On Mon, Dec 13, 2021 at 9:40 AM Shruthi Gowda <gowdashru(at)gmail(dot)com> wrote:
> > > I am reviewing another patch
> > > "v5-0001-Preserve-relfilenode-and-tablespace-OID-in-pg_upg" as well
> > > and will provide the comments soon if any...
>
> I spent much of today reviewing 0001. Here's an updated version, so
> far only lightly tested. Please check whether I've broken anything.
> Here are the changes:

Thanks, Robert for the updated version. I reviewed the changes and it
looks fine.
I also tested the patch. The patch works as expected.

> - I adjusted the function header comment for heap_create. Your
> proposed comment seemed like it was pretty detailed but not 100%
> correct. It also made one of the lines kind of long because you didn't
> wrap the text in the surrounding style. I decided to make it simpler
> and shorter instead of longer still and 100% correct.

The comment update looks fine. However, I still feel it would be good to
mention on which (rare) circumstance a valid relfilenode can get passed.

> - I removed a one-line comment that said /* Override the toast
> relfilenode */ because it preceded an error check, not a line of code
> that would have done what the comment claimed.
>
> - I removed a one-line comment that said /* Override the relfilenode
> */ because the following code would only sometimes override the
> relfilenode. The code didn't seem complex enough to justify a a longer
> and more accurate comment, so I just took it out.

Fine

> - I changed a test for (relkind == RELKIND_RELATION || relkind ==
> RELKIND_SEQUENCE || relkind == RELKIND_MATVIEW) to use
> RELKIND_HAS_STORAGE(). It's true that not all of the storage types
> that RELKIND_HAS_STORAGE() tests are possible here, but that's not a
> reason to avoiding using the macro. If somebody adds a new relkind
> with storage in the future, they might miss the need to manually
> update this place, but they will not likely miss the need to update
> RELKIND_HAS_STORAGE() since, if they did, their code probably wouldn't
> work at all.

I agree.

> - I changed the way that you were passing create_storage down to
> heap_create. I think I said before that you should EITHER fix it so
> that we set create_storage = true only when the relation actually has
> storage OR ELSE have heap_create() itself override the value to false
> when there is no storage. You did both. There are times when it's
> reasonable to ensure the same thing in multiple places, but this
> doesn't seem to be one of them. So I took that out. I chose to retain
> the code in heap_create() that overrides the value to false, added a
> comment explaining that it does that, and then adjusted the callers to
> ignore the storage type. I then added comments, and in one place an
> assertion, to make it clearer what is happening.

The changes are fine. Thanks for the fine-tuning.

> - In pg_dump.c, I adjusted the comment that says "Not every relation
> has storage." and the test that immediately follows, to ignore the
> relfilenode when relkind says it's a partitioned table. Really,
> partitioned tables should never have had relfilenodes, but as it turns
> out, they used to have them.
>

Fine. Understood.

Thanks & Regards,
Shruthi KC
EnterpriseDB: http://www.enterprisedb.com