On Wed, Aug 08, 2012 at 04:08:03PM -0400, Wietse Venema wrote:
> email builder:
> > Postfix expects an empty set (i.e. no rows returned) if it is to respond
> > negatively that a virtual alias does not exist.
> > Returning NULL does not equal no rows returned.
>
> email builder:
> >Are you sure??
>
> 100% confirmed. To return NOTFOUND, you MUST return NO RESULT.
The common code that underlies the MySQL, PgSQL and LDAP table
drivers ignores empty result values with a warning. While NULL
result values are silently ignored you should not depend on this
undocumented behaviour.
We should update the documentation for empty results, right now
the documentation of "%s" in the result format only says that empty
results are skipped, without mentioning the warning and that queries
should not be constructed to yield empty result columns.
The situation with "%u" and "%d" in the result format is a bit more
subtle, since these are potentially empty parts of a non-empty
address, so no warnings are issued when "%u" or "%d" are empty,
but the result value is still skipped.
--
Viktor.
