Re: improve CREATE EXTENSION error message

"Bossart, Nathan" <bossartn@amazon.com> writes:
> Currently, if you attempt to use CREATE EXTENSION for an extension
> that is not installed, you'll see something like the following:

>         postgres=# CREATE EXTENSION does_not_exist;
>         ERROR:  could not open extension control file "/usr/local/pgsql/share/extension/does_not_exist.control": No
suchfile or directory 

> I suspect this ERROR message is confusing for novice users, so perhaps
> we should add a HINT.

If we issue the hint only for errno == ENOENT, I think we could be
less wishy-washy (and if it's not ENOENT, the hint is likely
inappropriate anyway).  I'm thinking something more like

HINT:  This means the extension is not installed on the system.

I'm not quite satisfied with the "on the system" wording, but I'm
not sure of what would be better.  I agree that we can't just say
"is not installed", because people will confuse that with whether
it is installed within the database.

            regards, tom lane