When creating a new TChain and invoking GetEntry on it for a given entry, that call reads multiple clusters instead of just the one where the entry belongs.
In particular, it has been observed that all the clusters starting from the one of the entry until the end of the file are read.
A ROOT file from the TOTEM experiment has been used as input. The following code triggers the issue, when trying to read branch "track_rp_5.y". Entry 467370 is the first of the n-1 cluster in the file. The code triggers the reading of the n-1 and n clusters in the file, instead of just the n-1.
The following code, with TTreeReader, triggers the same issue:
On the contrary, the following code has the correct behaviour, i.e. it only reads the n-1 cluster.
The number of bytes read is measured by invoking