[Paraview] Extract Block not working properly?

[OSHIMA Takuya]

Hi,

The recent major changes in composite datasets for the CVS head looks
very intersting. However I have a problem: the Extract Block filter
for a single node with multiple datasets doesn't work as intended.

That is, when I only have Node 0 under Root, even if I deselct some of
the datasets under the node I still see the complete detasets as
output. But if I have 2 nodes under Root and deselect some of the
datasets under Node 0, Extract Block works exactly as intended
(removes deselcted datasets).

Further, I found by removing the following code at lines 109-114 of
ParaView3/VTK/Graphics/vtkExtractBlock.cxx the filter works as
intended for a single node composite dataset.

  if (this->Indices->find(0) != this->Indices->end())
    {
    // trivial case.
    output->ShallowCopy(input);
    return 1;
    }

I wonder what is the intension of this piece of code...?

Regards,
Takuya