On 11/2/21, 8:11 AM, "Robert Haas" <robertmhaas@gmail.com> wrote:
> Why in the world would you want a plain hook rather than something
> closer to the way logical replication works?
>
> Plain hooks are annoying to use. If you load things at the wrong time,
> it silently doesn't work. It's also impossible to unload anything. If
> you want to change to a different module, you probably have to bounce
> the whole server instead of just changing the GUC and letting it load
> the new module when you run 'pg_ctl reload'.
Well, the current patch does require a reload since the modules are
preloaded, but maybe there is some way to avoid that. However, I
agree with the general argument that a dedicated archive module
interface will be easier to use correctly. With a hook, it could be
hard to know which library's archive function we are actually using.
With archive_library, we know the exact library's callback functions
we are using.
I think an argument for just adding a hook is that it's simpler and
easier to maintain. But continuous archiving is a pretty critical
piece of functionality, so I think it's a great candidate for some
sturdy infrastructure.
Nathan