Prepared statements fail after schema changes with surprising error

A user reported an interesting issue today. After restoring a dump created
with --clean on a running application in his development environment his
application started complaining of missing tables despite those tables very
clearly existing.

After a little thinking, we determined that this was due to the now-default
behaviour of Rails to create prepared statements for most queries. The
prepared statements error out because the old relation they point to is
missing, but this gives a misleading report thus:

PG::Error: ERROR: relation "xxx" does not exist

I'm not sure what the best outcome here would be. A very simple solution
might be to expand the error message or add a hint to make it descriptive
enough that a user might be able to figure out the cause on their own
without happening to have the unusual intersection of Rails and Postgres
internals knowlege I (unfortunately) possess. A better solution might be to
attempt to re-prepare the statement before throwing an error.

-pvh

--
Peter van Hardenberg
San Francisco, California
"Everything was beautiful, and nothing hurt." -- Kurt Vonnegut