Disabling fast cloning on data products with updated checksum
fastCloning fails when the running data product definition is changed respect to the one stored in the input ROOT file.
Failure mode is currently via exception.
fastCloning is possible from job configuration on a per-job basis, and it affects all the data products in the same way.
LArSoft would like the possibility to disable fast cloning on a per-data product basis, and even better it would be if art could detect when that is needed for each product.
This would make run-time schema evolution completely automatic for the experiments.
#1 Updated by Christopher Backhouse about 3 years ago
In practice NOvA's fcls are all littered with
fastCloning: false, so we never get the benefits of fast cloning even in the cases where it could have been used, and having to add those lines is one of the most common gotchas for new users.
So, I'm definitely in favour of (the automatic part of) this request.
#3 Updated by Paul Russo about 3 years ago
It should be noted that ROOT 6 does not currently support cloning individual branches of a tree, cloning is a whole-tree operation.
However it is still possible for art to issue an informational message when it is not possible to clone a branch and continue on copying branches event-by-event in the normal manner without throwing an exception and ending the job.