Re: BUG #15686: pg_dump: server version: 11.2; pg_dump version: 11.2

PG Bug reporting form <noreply(at)postgresql(dot)org> writes:
> I recently installed PostgreSQL 11.2 (we were formerly using 9.5.3) and ran
> our tests. One of our tests performs a `pg_dump` and I receive the following
> error:

> 2019-03-08 16:43:54.417 [ 123 ] [INFO ] Starting database (dir) dump with:
> /path/to/postgresql/bin/pg_dump --file /path/to/file database_name
> 2019-03-08 16:43:54.429 [ 123 ] [ERROR] pg_dump: server version: 11.2;
> pg_dump version: 11.2
> 2019-03-08 16:43:54.429 [ 123 ] [ERROR] pg_dump: aborting because of server
> version mismatch

That's pretty bizarre-looking, isn't it. Looking at the code, I suspect
that the problem is that your pg_dump is linking to an old version of
libpq.so. Although what pg_dump is printing for "server version" is
the string received from the server, the actual version comparison is
done numerically and it depends on how libpq's PQserverVersion() function
parsed the string. In the 9.5 branch, the earliest version that would
have done the right thing for new-style two-part server version numbers
was 9.5.4.

Hence, you need to make sure your old libpq library gets replaced by
the new installation, or that your loader search path finds wherever
you've decided to put the new library.

regards, tom lane