RE: Handling ROOT files

["Mark Pollack" <markp@bnl.gov>]

Hi,
There is no file ID (or system name in objy lingo) for ROOT file in a
central repository.
Just the file name, no different than if it was an ascii file.  The list of
file names could be generated by a listing of files in HPSS directories.
There is a TChain class that represents a collection of root files which
will be used for an analysis pass.  It has methods to get the list of files
in the chain and so on.
http://root.cern.ch/root/html/TChain.html
I guess the ROOT Tagdb could have for each entry the filename and event
number, even though seems a bit wasteful, it might be an easy direct
approach.  The data is compressed before writing to disk so it will not be
such a big deal.  Since the Tagdb for the ROOT version has yet to be
designed it can contain whatever information needed.  One could pass the
list of filename + event IDs in that file to analysis code.
Mark




-----Original Message-----
From:	Arie Shoshani [mailto:arie@math.lbl.gov]
Sent:	Tuesday, December 15, 1998 4:41 PM
To:	morrison@bnl.gov; DLOlson@lbl.gov
Cc:	gcdev@sseos.lbl.gov
Subject:	Handling ROOT files

Dave and Doug,

We started thinking about what it will take to handle ROOT
files by the Storage manager.   We have a couple of
questions.

1)  In order to use the SM now, we assume that files have
file IDs (in addition to names).  Are file IDs assigned to
ROOT files?

2)  Currently, the CM gets the file names (as they are used
by HPSS) from the Objectivity catalog.  Where would these
names exist with ROOT files?

3)  Would the ROOT Tagdb have all the necessary information
about the components of each event?  i.e. the file_name and
location in file for each component?  If so, what will be
passed to the EIs is the same as now: with every "file
bundle" cached we will pass simply a set of event_ids that
qualify for that query in that file.

Please comment.

Thanks, Arie.