On Fri, Apr 19, 2013 at 11:46 AM, Michael Bayer <mike...@zzzcomputing.com> wrote: > > On Apr 19, 2013, at 1:56 PM, Dan Lenski <dlen...@gmail.com> wrote: > >> The problem I'm having is... how can I figure out what are the appropriate >> type objects for this comparison if I *only* have access to the cursor object? > > > Basically I'd question that precondition. I'd look into how the system is architected such that only a cursor is passed around, and try to substitute it/augment it with some kind of contextual object; either an object that can refer back to the DBAPI types, or even the DBAPI module itself. You can't really assume that ".connection" is present, nor that the Connection class of the DBAPI is in the same module space as where the type objects are defined. I'd rework the system and refuse the temptation to guess.
I agree that my solution is not a good one... just a quick hack which seems to work for the modules that I've tried so far. However, it seems to me that the precondition is a reasonable one: the cursor object provides a DB-independent means of obtaining the data from a query, so why not the metadata as well? Actually, the DBAPI is pretty good in that regard, because it does establish the different type objects which a module must provide... but doesn't give a clear way to *find* those type objects from the cursor object. This makes it difficult to write truly DB- independent code to manipulate cursor objects. I *could* pass around a handle to the DB module along with the cursor itself, as you've suggested, but that seems redundant and error-prone to me. To my mind, this is a small gap in the DBAPI design: (1) DBAPI does specify a set of module-dependent type objects against which column type objects are to be compared (2) DBAPI does specify a cursor object which will produce column type objects after a query is executed (3) DBAPI *doesn't* provide any way to get from the cursor object to the module-defined type objects, at least not without passing a around module- dependent object. _______________________________________________ DB-SIG maillist - DB-SIG@python.org http://mail.python.org/mailman/listinfo/db-sig
