Re: Objy/ROOT discussion at today's phone meeting

[Henrik Nordberg <HNordberg@lbl.gov>]

Doug Olson wrote:
> 
> > >   Can anyone allay my concerns?  Does anyone else share them?
> > I'm convinced! I share your concern
> 
> I also share these concerns.  Using the Objy catalog for the
> ROOT file catalog can be coerced to work for MDC2 but
> is certainly not a good long term solution (where long term
> can be quite short).

For the long term, I propose:
If we use ROOT files _only_, it is no problem for the Query 
Estimator/index builder to make a mapping from file name to
FID to be used internally by the Storage Manager.
If there will be a mix of Objy and ROOT files, then the problem
of uniqueness arises. I.e., QE has to choose FID's that aren't
in use and won't become used by Objy. This could be solved by
having the index builder scan the Objy catalog and generate 
FID's that are not already taken, _each time_ new files 
(ROOT or Objy) are added.

> Another weak spot is assuming that all files are in
> a single HPSS directory.  This is not very useful for

For MDC2 the index building process and the QE can handle
that files for different components being in different
directories on HPSS. This information is passed through
the component.hpss.paths file in the index building
process (the details of which are yet to be released, but
I'll do that soon).
Luis, does the Cache Manager handle this?

This is not a full solution. I would not be surprised if
people want different runs in different directories, for
example.
Is this issue important? If it is, then we will put more
effort into solving it.

 - Henrik

> real data, but also can be coerced to work in MDC2
> because of the ability to make links in HPSS
> by using HSI.  I did some looking around about a month
> ago for "file catalog" ideas but did not really find anything.
> A file catalog that maintains file ID's as well as pathname
> mappings for HPSS and disk locations does not seem like a
> particularly difficult database application, but I did not
> find an implementation.
> 
> Doug
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