Re: [Pytables-users] append to multiple tables

[Edward V. <edw...@gm...>]

Yes, exactly.
I'm pulling data out of C that has a 1 to many relationship, and dumping it
into pytables for easier analysis. I'm creating extension classes in cython
to get access to the C structures.
It looks like this (basically, each cv1 has several cv2s):

h5.create_table('/', 'cv1', schema_cv1)
h5.create_table('/', 'cv2', schema_cv2)
cv1_row = h5.root.cv1.row
cv2_row = h5.root.cv2.row
for cv in sf.itercv():
    cv1_row['addr'] = cv['addr']
    ...
    cv1_row.append()
    for cv2 in cv.itercv2():
        cv2_row['cv1_addr'] = cv['addr']
        cv2_row['foo'] = cv2_row['foo']
        ...
        cv2_row.append()
    h5.root.cv2.flush()  # This fixes issue

Adding the flush after the inner loop does fix the issue. (Thanks!)
So, my followup question, why do I need a flush after the inner loop, but
not when moving from the outer loop to the inner loop?

Thanks!



On Mon, Jun 10, 2013 at 2:48 PM, Anthony Scopatz <sc...@gm...> wrote:

> Hi Ed,
>
> Are you inside of a nested loop?  You probably just need to flush after
> the innermost loop.
>
> Do you have some sample code you can share?
>
> Be Well
> Anthony
>
>
> On Mon, Jun 10, 2013 at 1:44 PM, Edward Vogel <edw...@gm...>wrote:
>
>> I have a dataset that I want to split between two tables. But, when I
>> iterate over the data and append to both tables, I get a warning:
>>
>> /usr/local/lib/python2.7/site-packages/tables/table.py:2967:
>> PerformanceWarning: table ``/cv2`` is being preempted from alive nodes
>> without its buffers being flushed or with some index being dirty.  This may
>> lead to very ineficient use of resources and even to fatal errors in
>> certain situations.  Please do a call to the .flush() or .reindex_dirty()
>> methods on this table before start using other nodes.
>>
>> However, if I flush after every append, I get awful performance.
>> Is there a correct way to append to two tables without doing a flush?
>> Note, I don't have any indices defined, so it seems reindex_dirty()
>> doesn't apply.
>>
>> Thanks,
>> Ed
>>
>>
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