Re: Doubt about TTree Branch

From: Rene Brun <>
Date: Sun, 27 Mar 2005 10:48:59 +0200 (MEST)

Unless you reference ALL variables in a query, it is always better to store one variable per branch.
 -the file size will be smaller because the compression algorithm   will work better on homegeneous variables  -you minimize the amount of I/O if your query references only   a subset of all the variables.

Note that we will come soon with a new class TTreeSQL that will allow you to query directly a SQL table as if it was a ROOT Tree.

Rene Brun

On Sat,
26 Mar 2005, Ivan Koji Koga wrote:

> Hello all,
> I have a database in mysql and i want to store it in ROOT TTree.
> I declared a ttree for one table and then i put all columns in a branch
> like:
> tree->Branch(“RoundTrip”, &roundtrip,
> “testid/I:microseconds:sourceid:destid:datetime/C:delay/F:jitter:loss”);
> What's the difference in performance if i do it with many branches like:
> tree->Branch("testid", &testid, "testid/I");
> tree->Branch("microseconds", &microseconds, "microseconds/I");
> and so on...
> I saw in the userguide that if you have some related variables you have
> to put it together in the same branch. I think that my data is related
> because they are all in the same table and have values linked.
> Thank's in advance,
> Ivan K. Koga
Received on Sun Mar 27 2005 - 10:49:05 MEST

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