Another thought about search_path semantics

Back in 9.2 (commit 880bfc328) we decided that nonexistent schemas listed
in search_path should be silently ignored, reasoning by analogy with Unix
PATH settings where nonexistent directories in the path don't result in
error reports.  This remains imperfect though, cf commit 15386281a and
the similar report today at
http://www.postgresql.org/message-id/533ED1EC.4080102@abshere.net

It strikes me that the real issue here is that the analogy to PATH is
fine for search_path's role as a *search* path, but it's not so good for
determining the creation target schema.  I wonder if we should further
redefine things so that the creation target schema is always the first
thing named in search_path, and if that doesn't exist, we throw an
error rather than silently creating in some schema further down the
list.

Thoughts?
        regards, tom lane