Hi, I have several TTrees in a TFile. I wish to “reprocess” the data, that is to say, replace a TTree with a new one. Well, I could just create a new TFile, clone the TTrees I want to keep and compute the new TTree. However, that proves to be lengthy in the case where I have several large TTrees t…

Thanks for pointing this to me. I missed it. Very instructive ! In short, for people reading this post, the ‘deletion’ must be done from the TTree , and not from the key (so that the space occupied by the baskets (data) in the file is also reclaimed). TTree* t = (TTree*)fin.Get("subtract"); t->Del…

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Delete TObject in TFile and use the freed space

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Wile_E_Coyote April 5, 2018, 10:01am 4

File size with a CloneTree ROOT

Hi, I d like to modify a tree and overwrite it in the same file and this several time. I have an issue with the file size. To summarise the problem I got to this piece of code which I would assume do nothing, but unfortunately it increases the file size. void example(void) { string filename = "example.root"; string treename = "tagsDumper/trees/gjet_13TeV_TTHHadronicTag"; string writingDir = "tagsDumper/trees/"; TFile *file = new TFile( filename.c_str(), "update" ); file->cd(wr…

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