pytables-users

[Pytables-users] Any way to link tables?

[chuck c. <cc...@zi...>]

Quick question...I have a datafile with the structure
root.service._20040301
            ._20040302
                ....
            ._20040331

Where _YYYYMMDD is a table full of stats detailing the performance of the
particular service over a day at one minute intervals.  Each day I do some
analysis on the table for that day for all the services I'm monitoring and
it has worked out really well.

Now, it is the end of the month and I'd like to do a summary for the
month.  I've been able to generate that monthly summary for all statistics
except one from the daily summaries.  However, for this last stat I need
to look at all datapoints.  Is there a way that I can "link" tables so
that when I traverse all the rows in _20040301 my row iterator
automatically continues on to _20040302?

I can do it with a for loop or even write a facade that makes a list of
tables look like one table but I wanted to make sure this wasn't a bit of
functionality that already exists which I am missing.

Also Francesc, in the last email you replied to me that you hadn't had
time to incorporate timestamps into PyTables yet.  I went back to the
apache site and found this link:
http://hdf.ncsa.uiuc.edu/HDF5/doc/H5.intro.html#Intro-ODatasets where it
says:
"Atomic classes include integer, float, date and time, string, bit field,
and opaque. (Note: Only integer, float and string classes are available in
the current implementation.) "

Do I read this incorrectly, even if you had the time you couldn't truly
implement it on top of HDF5 since HDF5 doesn't support it yet.

cheers,
chuck

Re: [Pytables-users] Any way to link tables?

[Francesc A. <fa...@py...>]

Hi Chuck,

A Dijous 06 Maig 2004 18:53, chuck clark va escriure:
> Now, it is the end of the month and I'd like to do a summary for the
> month.  I've been able to generate that monthly summary for all statistics
> except one from the daily summaries.  However, for this last stat I need
> to look at all datapoints.  Is there a way that I can "link" tables so
> that when I traverse all the rows in _20040301 my row iterator
> automatically continues on to _20040302?
> 
> I can do it with a for loop or even write a facade that makes a list of
> tables look like one table but I wanted to make sure this wasn't a bit of
> functionality that already exists which I am missing.

I understand what you want to do, but this is not currently implemented in
PyTables, so you will need to write the code for yourself (it shouldn't be
complicated, I guess). I am pondering to add soon reference support in
pytables, and eventually support this kind of table-chain iterator. No
promises, though.

> Do I read this incorrectly, even if you had the time you couldn't truly
> implement it on top of HDF5 since HDF5 doesn't support it yet.

No, you read well, but I think this documentation is outdated (HDF5 1.4). Go
to this one: http://hdf.ncsa.uiuc.edu/HDF5/doc/UG/index.html and follow the
"Datatypes" hyperlink. This documentation is updated to HDF5 1.6.2 and seems
like if time and data support *is* there.

Cheers,

-- 
Francesc Alted