I wrote:
> I looked through all the callers of pg_do_encoding_conversion(), and
> AFAICS this change is a good idea. There are a whole bunch of places
> that use pg_do_encoding_conversion() to convert from the database encoding
> to encoding X (most usually UTF8), and right now if you do that in a
> SQL_ASCII database you have no assurance whatever that what is produced
> is actually valid in encoding X. I think we need to close that loophole.
BTW, a second look confirms that all but one or two of the callers of
pg_do_encoding_conversion() are in fact converting either to or from
the database encoding. That probably means they ought to be using
pg_any_to_server or pg_server_to_any instead, so that they can take
advantage of the pre-cached default conversion in the not-unlikely
situation that the other encoding is the current client_encoding.
This would imply that we ought to put a validate-if-source-is-SQL_ASCII
step into pg_server_to_any() as well, since that function currently
short-circuits calling pg_do_encoding_conversion() in that case.
regards, tom lane