[DB-SIG] parameter and column binding (date/time handling)

[M.-A. Lemburg]

Christoph Zwerschke wrote:
> Andy Todd wrote:
>  > I don't know about the mechanism, but my preference for any DB-API 
> module would be stdlib first and then mx.DateTime.
> 
> Ok, I think I will do that. Otherwise, as soon as an administrator 
> installs mx.DateTime, some non-related DB-API 2 applications may 
> suddenly break.

Database modules should never choose a type mapping based
on import testing.

If a module has a default of using mxDateTime and the package
can't be found, it should raise an import error instead of
silently reverting to Python's datetime or another type.

> Of course you will then get a problem if the 
> administrator upgrades from Python 2.2 to 2.3, but you expect some 
> things to break anyway in such a case (and he should have done that a 
> long time ago anyway ;-)
> 
> Still, I'm looking for a way to explicitely tell the module to use mx or 
> stdlib dates, or other date formats.

I think we'd need something that does the following:

Parameter binding:

* allows mapping based on:
  - parameter position in the statement
  - parameter type (the database type code, if the database can
    provide this information)

* allows assigning a binding function that converts the Python
  object to whatever the database requires (these will have to
  be database specific)

  These binding functions will then have to implement e.g.
  "bind the Python object as VARCHAR".

Result set types:

* allows mapping based on:
  - column position
  - column type (the database type code)

* allows assigning a binding function that converts the database
  type to a Python object (these will have to be database specific)

  These binding functions will have to implement e.g.
  "convert the database type to a Python float".

Given that mapping on both position and type is hard to
implement using dictionaries and that setting the binding
functions is usually only done once per query, I think that
using a callback to implement these mappings would be the
most flexible way.

-- 
Marc-Andre Lemburg
eGenix.com

Professional Python Services directly from the Source  (#1, Aug 07 2006)
>>> Python/Zope Consulting and Support ...        http://www.egenix.com/
>>> mxODBC.Zope.Database.Adapter ...             http://zope.egenix.com/
>>> mxODBC, mxDateTime, mxTextTools ...        http://python.egenix.com/
________________________________________________________________________

::: Try mxODBC.Zope.DA for Windows,Linux,Solaris,FreeBSD for free ! ::::