Hi list,

Unfortunately, my spam filter decided to junk all the replies to this
thread. I only uncovered them a few days ago and finally have the time
to reply to them, sorry for that!

On Thu, 2009-07-30 at 13:07 +0200, Sebastien Binet wrote:
> David,
> 
> > > > For python users, there is pyROOT. Of course, we know and love
> > > > pytables. We're going to test several things
> > >
> > > please do keep me in the loop (being the librarian of pytables for Atlas)
> > > of your findings.
> >
> > Will do! Atlas uses pytables? For what exactly?
> AFAICT, right now it is just for private user analyses, mostly for people 
> having been burned with ROOT.

I can't really say I've been _burned_ by ROOT, it's just that I hated
the output and the 'language' on first sight and have been putting off
actually using it. I've been quite successful at that, at least until
this day. However, I've seen pretty nice things being done with ROOT and
of course, it _is_ one of the most well-tested analysis frameworks out
there, whether you like it or not.

It's just that I love python, the enormous amount of libraries which
allow you to tie together almost anything you can dream up and things
like PyTables, IPython and the Enthought libraries only make that better
and better!

> > > > We've asked around what large experiments (LHC experiments like ATLAS)
> > > > are using and they are _not_ using db's for storage.
> > >
> > > I am a bit surprised by this statement as we do use Oracle and/or SQLite
> > > (via an abstraction layer) for conditions data (detector geometry, time
> > > dependent calibration 'constants',...) - not much for event data though.
> >
> > We've specifically asked about event data. Right now that basically
> > means from simulations, but IIUC the same will hold for collisions. Raw
> > data in ROOT files, metadata in Oracle (apparently a very nice site-wide
> > license), followed by some talk about multi-tiered setups and the
> > perceived problems of congregating metadata from a final tier back into
> > the central Oracle database.
> >
> > Still, take my comments as from someone who just asked around, and is
> > not part of Atlas. Misrepresentation is entirely my fault.
> >
> > > BTW, being able to automatically translate an sqlite file (or directly
> > > read) to an hdf5/pytables one (and vice-versa) would be interesting... (I
> > > haven't even tried, it seems rather straight forward so probably the
> > > script already exists)
> >
> > For what is sqlite used? Seems like a strange solution to me when you
> > already have oracle, pytables and root.
> sqlite snapshots of the master oracle database are shipped over the Grid to 
> ease a bit the load on the oracle server(s).

Oh, wow. Talking about David and Goliath...

> sqlite is also usually used a lot during development, for the same reasons as 
> above and also b/c it is easier to deploy on Joe the user's laptop :)

Yes, indeed!

> 
> >
> > Seems straightforward indeed. Something like (pseudo-code):
> >
> > sql = "select * from events"
> > cursor.execute(sql)
> >
> > for result in cursor.fetchall():
> >     tablerow['event_id'] = result[0]
> >     tablerow['timestamp'] = result[1]
> >     tablerow['n_jets'] = result[2]
> >     tablerow.append()
> >
> > table.flush()
> right, but this assumes some a priori knowledge of the event schema...
> anyways, probably not the right list to discuss this :)

We'll just have to move to the pytables-physics list then, ;-)

David


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