Offline access to QCDB

Dear experts,

our team is currently working on the post-processing of the MFT.
We were wondering if there is a way to access the data stored in the QCDB that would not require using the full framework for trending, which seems unnecessarily too complex for our needs at the moment. To be more specific, all we would need is a macro (which could be run offline after a run) to access values from a given histogram from the QCDB. Is it possible to do so without using the post-processing interface?


Hi Diana,

I am no expert but maybe these command line tools fit your needs. This should also work for qcdb, since (at least up to some point) ccdb and qcdb were the same. For the test instance this is still the case.

For getting the qc objects it should be enough to provide a path starting with /qc (see here) to the o2-ccdb-downloadccdbfile function. E.g.

o2-ccdb-downloadccdbfile --path /qc/MFT/MO/<TaskName>/<ObjectName> --dest <someDestination> --timestamp <someNumber>

then you should get the desired object. IIRC timestamp = -1 gives the most recent object with that name.

Another option would be to use an instance of o2::ccdb::CcdbApi in the macro. The retrieveFromTFileAny is the function to use, I think (see here).