> Valeri mentioned about TTable class.
[Valeri Fine]
TTable is a self-defined array of C-structures.
It occupies a continuous area in memory and in file.
The table object can not be read by piece. It is always read in as
whole thing.
In our applications (STAR/ATLAS) we have what we call "an event". Each
event may contain several different tables organized heirachically. Each
event is stored separately and can be read back in the random order or
sequentially. To look up the table a separate TTableSorter class is
provided also (see: http://root.cern.ch/root/htmldoc/TTableSorter.html )
Web site has several simple examples of how this class can be used
http://www.usatlas.bnl.gov/computing/software/db/htmldoc/examples/
To try them one may download these examples and replace there the name
of the share library. One needs to replace the statement:
gSystem->Load("libRootKernel");
with
gSystem->Load("libTable");
there.
> Maybe that is another thing to try.
> Anyone knows the fundamental difference between TTable and TTree
> in terms of how they organize the data on disk ??
[Valeri Fine]
TTable is store row-wise, TTree is stored column-wise.
The memory and disk space for TTable is allocated at ones as one piece.
[Valeri Fine]
The picture http://root.cern.ch/root/html/gif/tree_layout.gif gives some
info about TTree layout.
>
> --HP
>
>
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