[DB-SIG] PEP249 - Proposed change to DB-API 2.0

[M.-A. Lemburg]

Greg Stein wrote:
> 
> On Fri, Apr 27, 2001 at 01:24:53PM +0200, M.-A. Lemburg wrote:
> > Harri Pasanen wrote:
> > > [Making the DB API interface handle multiple paramstyles]
> > >
> > > How about specifying a single 'python meta' -style.  So the module
> > > writers would support the database native format, and the Python DB-Api
> > > format, from which a conversion to native format would exist.  I spent
> > > maybe 2 minutes thinking about it, so maybe this is not feasible, just a
> > > thought...
> >
> > This is not necessarily efficient, e.g. MySQL and Postgresql are
> > just fine with wrapping data up in the SQL statement itself,
> > but e.g. many ODBC drivers pass in data using column binding and
> > only parse the SQL once (parsing and checking for correctness
> > takes a long time...) !
> >
> > I'd rather leave it at the current open state of affairs. People who
> > want to use a generic interface can use wrappers or Chris' dbhelper.py
> > module if they want to.
> 
> Normally, I like to jump in on these discussions and chatter on about the
> API, its view of the world, and how it helps authors and users, and ...
> 
> But damn. Marc-Andre has said everything exactly as I would. I've got
> nothing more to add! Dang :-)

Hehe :-)
 
> [ hmm. maybe I've hounded M-A enough over the past five years, that I've
>   brainwashed him? :-) ]

Probably... :-)

> I support the suggestion that a DBAPI module can *optionally*: advertise
> multiple paramstyles, and allow switching the paramstyle "mode". As always,
> there should be a way for a module author to ignore this option as too much
> hassle for themselves (and punt to an external system). So if PEP-249 is
> revamped to make the "add'l paramstyles" optional, then I'd be +1.

Same here. I'd suggest to use cursor and connections methods
for setting or querying the current paramstyles in use:

.get_paramstyle()
     Returns one of the defined paramstyle strings currently
     in effect.

.get_paramstyles()
     Returns a list of possible paramstyles.

.set_paramstyle(paramstyle)
     Sets the paramstyle for the next statement executed on 
     the cursor to paramstyle.

The module level .paramstyle should be set to the default
paramstyle which the module expects without calling .set_paramstyle().

As for most cursor level flags, the connection should offer
the same APIs and then inherit the setting to all newly
created cursors on that connection.
 
> The param styles were chosen with the explicit intent that the DBAPI module
> would not even touch the strings. The "?" and ":1" and ":name" forms can all
> be passed directly to certain SQL engines, along with input bindings.
> "Lesser" databases require munging everything into a single SQL string,
> which means they have more flexibility on the param style.

Right.

-- 
Marc-Andre Lemburg
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