[DB-SIG] About LOB

Chris Clark Chris.Clark at ingres.com
Wed Apr 27 19:05:25 CEST 2011

Kwon, Chan Young wrote:
> I am implementing new DB API for new Database according to DB API 2.0. (as C-Extension)
> There is no specification about LOB in DB API 2.0
> Especially, I need LOB object for piecewise LOB writing/reading after query execution.
> So I defined my own LOB object.
> I tried to make simple and easy interface for LOB.

BLarge OBject's (BLOBs) are alluded to in pep 249 BUT they really are
not detailed so I think you have spotted a weakness in the spec. CLOBs
(Character Large OBjects) are not covered at all. Locators are not
discussed but implied by references to bufferobjects.

For BLOBs as input bind parameters check out the Binary() constructor
(case sensitive) at http://www.python.org/dev/peps/pep-0249/.
For BLOB results look for bufferobject in

The spec (as I read it) really expects LOBs to be handled as one massive
block. However implementators can choose to implement locators behind
the scene so that data isn't sent across the wire unless the buffer
object is read from.

So, model your LOB access methods on bufferobjects and you should be all
set! Marc-Andre reads/responds to the list regularly so take note of any
suggestions he has :-)

Hope that helps get you started.


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