Martijn van Oosterhout <kleptog@svana.org> writes:
> So the idea is to force failure when it would otherwise succeed, not
> just for the pretty error messages but for stability of the system.
Exactly. Peter's right that we'd not always get a "nice" error message
--- but it's not hard to figure out "unresolved symbol" failures.
As we just were reminded, it can be really hard to figure out minor
incompatibilities with wrong-version libraries, and the real point of
the proposal is to save us from going through *that* again.
> I would be in favour if storing the CATALOG_VERSION in the pg_finfo
> struct and rejecting anything that doesn't match.
Not sure that CATALOG_VERSION is an amazingly useful thing to use.
I think the major version number (eg "8.1") would be sufficient,
and it'd certainly give error messages that meant more to the casual
user.
The problem with CATALOG_VERSION is that we bump it basically for
changes in the on-disk contents of a freshly initdb'd database, which
does not have all that much to do with the ABI seen by a shared library.
To have something useful that is finer-grain than major version number,
I think we'd need to invent a separate version number that could be
bumped whenever we made incompatible changes in in-memory structures
or function APIs. Which'd be almost every day during development :-(
I don't think it's worth trying to do that. People who work with
development tip should know to recompile their libraries whenever they
recompile the main system.
regards, tom lane
