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A Thursday 19 November 2009 14:02:27 pytables-users-
boun...@lists.sourceforge.net escrigué:
> Hello,
>
> I was wondering why it's not possible to use the "filters" parameter with
> createArray (just like with createTable) to ask for compression ? In other
> words, when I use ptrepack with option --complevel=1, if my hdf5 file only
> contains leaves created from numpy arrays with createArray, no compression
> is done.
>
> For example :
> import numpy as N
> import tables
>
> z = N.ones(10e6)
> filters = tables.Filters(complevel=1)
> myfile = tables.openFile('./temp.h5', 'a', filters=filters)
> myfile.createArray(myfile.root, 'z', z) # in this case no compression is
> done z_table = N.rec.fromarrays(z, names='z')
> myfile.createTable(myfile.root, 'z_table', z) # compression is ok
Yes. From the `Array` description in the Reference chapter of the UG:
"""
This class provides methods to write or read data to or from array objects in
the file. This class does not allow you neither to enlarge nor compress the
datasets on disk; use the EArray class (see Section 4.9) if you want
enlargeable dataset support or compression features, or CArray (see Section
4.8) if you just want compression.
"""
This is because the `Array` creates a non-chunked dataset in the underlying
HDF5, and this sort of datasets cannot be compressed.
>
> Thank you for your help,
>
> Jean-Baptste Rudant
>
--
Francesc Alted
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