| Subject: | type_info fails when open statement handle - suggest workaround |
On recent versions of MSSQL code like the following will break:
my $sth = $dbh->prepare('select 5');
execute $sth;
my $type = $dbh->type_info($sth->{TYPE}->[0]);
It fails with 'cannot call method execute on an undefined value'.
type_info_all tries to do
my $sth = $dbh->prepare("sp_datatype_info");
but this fails because there is already an active statement handle.
I believe that older MSSQL versions, as well as Sybase, were more
tolerant somehow so you could call sp_datatype_info even with an open sth.
I tried the simple fix of calling
$dbh->selectall_arrayref("sp_datatype_info") but that doesn't help; it
still fails if there is an open statement.
What I suggest is two things:
- There should be a new global method to fetch all type info and cache
it for future calls to type_info. You could call this immediately after
connecting, if you are planning to use type_info later in the program.
(It could also happen on every connection, but I am reluctant to slow
down programs which don't need the type info.)
- type_info should catch the failure to prepare the statement handle and
give a more helpful error message, prompting the user to call the new
cache_type_info() method first before preparing a statement.
I started writing code for this, but I could not work out how to add a
new method to the database handle object, given that the RootClass
attribute on connection is not working (see previous bug). What do you
think?