On Feb 13, 2:11 pm, a...@svilendobrev.com wrote:
> On Friday 13 February 2009 11:07:29 koranthala wrote:
>
> > Hi,
> > I am working on a Python application which does approximately
> > 1000 updates at a time every 3 seconds in a Sqlite File Database
> > using SqlAlchemy. On timing it in a 2GHz machine, I found that it
> > is taking ~1.01 seconds to do the same.
> > Is it possible to increase the speed of the same? My
> > application is quite a complex one, and taking 1 second for the
> > updates is slowing the overall performance considerably.
> > I checked Sqlite page - and they mention that 25000 text
> > UPDATEs with an index (which is what I am doing) takes 2.4 seconds
> > (this is Sqlite2 data - sqlite3 should be faster). I guess should
> > mean that 1000 text UPDATEs should take 0.1 seconds.
>
> > The inserts I do is as follows:
> > BEGIN:
> > 2009-02-13 14:34:40,703 INFO sqlalchemy.engine.base.Engine.0x..10
> > UPDATE data SET status=? WHERE data."index" = ?
> > 2009-02-13 14:34:40,703 INFO sqlalchemy.engine.base.Engine.0x..10
> > ['True', 68762]
>
> > ...
> > (1000)
> > ...
>
> > COMMIT
>
> > Please note that the SET values are constant and only index
> > changes.
>
> can u use
> ... where data.index in (...) ?
> or if not,
> ... where data.index == 1 or data.index == 2 or ...
> group them by say 10 or 20, and see how faster that is?
Thank you for the quick reply. Your point seems very good.
Actually, I use SQLAlchemy's Identity Mapper to do the same.
The code I use is as follows:
for o in self.objects:
o.status = txt
self.session.add(o)
self.session.commit()
This acutally causes the SQLAlchemy to write separate UPDATE
statements.
I went through SQLAlchemy tutorial - and I couldnt find a mechanism to
cause it to update DB for multiple indexes in a single statement.
Is it possible to do it via Identity Mapper?
If not, if I modify it using SELECT statements, wont this session have
erroneous values?
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