A Monday 13 December 2010 09:34:25 Dominik Szczerba escrigué: > Hi Francesc, > > Thanks for confirming my guess. > I would vote for a different solution than removing this warning in > the 'expert' mode. > How about explicitly declaring ordering somewhere in pytables? > Or is this warning the only place where the ordering matters?
No, the ordering also affects the way iterators walk data on datasets. On a Fortran order dataset, the iterators should return slices orthogonal to the trailing dimension, not the leading one (default). Hmm, supporting Fortran order in PyTables is appealing, but I see a major drawback: there is not a standard way (that I'm aware of) for saving this metainfo in HDF5. So, unless the file has been created with PyTables, you will not be able to guess the data order. Having said this, PyTables has a feature that can 'fake' in some way a 'Fortran ordered' array. This is by using an EArray (just a HDF5 dataset with one of its dimensions that is set to be enlargeable; this dimension is called the 'main' dimension). EArrays are iterated through the enlargeable (main) dimension instead of the leading one. This is not exactly a Fortran-ordered dataset, but can be useful in some circumstances (specially for 2-dimensional arrays). OTOH, if what you want is to get rid of the warning, another solution is to play with the IO_BUFFER_SIZE and BUFFER_TIMES parameters: http://www.pytables.org/docs/manual/apc.html#id364831 until you reach a good balance for your datasets. Now that I think, it would be a good idea to add a hint about suggesting tailoring IO_BUFFER_SIZE and BUFFER_TIMES params in the warning rather than adding a brand-new EXPERT_MODE one. Updated ticket: http://pytables.org/trac/ticket/327#comment:1 -- Francesc Alted ------------------------------------------------------------------------------ Oracle to DB2 Conversion Guide: Learn learn about native support for PL/SQL, new data types, scalar functions, improved concurrency, built-in packages, OCI, SQL*Plus, data movement tools, best practices and more. http://p.sf.net/sfu/oracle-sfdev2dev _______________________________________________ Pytables-users mailing list Pytables-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/pytables-users
