Re: Minor version upgrades and extension packaging

Hi,

On 2018-02-11 21:50:32 -0500, Mat Arye wrote:
> We recently found that people who had compiled the TimescaleDB extension
> against 10.1 (or installed our binary versions via yum, apt, etc.) had
> their extension break when they upgraded to 10.2 due to changes of some
> underlying structs between the two minor versions.
>
> In particular, in the commit
> https://git.postgresql.org/gitweb/?p=postgresql.git;a=commitdiff;h=1597948c962a1407c01fc492c44917c097efa92e
> the structure of the ColumnDef struct changed. Since TimescaleDB uses an
> event hook that makes use of the ColumnDef structure, the TimescaleDB
> shared library compiled under 10.1 expected a different struct packing for
> ColumnDef than what was available in 10.2.

Ugh. I personally would say that's because that commit did stuff that we
normally trie hard not to do. While ColumnDef at least isn't serialized
into catalogs, we normally trie hard to break struct layout. Peter,
shouldn't that field at the very least have been added at the end?

> I had three questions:
>
> 1) Are similar changes to struct packing expected under minor postgres
> releases (we haven't encountered this issue before)?

Normally not.

> 2) Is it expected to have to recompile extensions for minor version
> upgrades of Postgres?

Normally only in extraordinary cases. There e.g. had been security
issues that required changes in PL handlers.

Greetings,

Andres Freund