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Posted to github@arrow.apache.org by GitBox <gi...@apache.org> on 2020/10/12 16:08:32 UTC

[GitHub] [arrow] lf-shaw opened a new issue #8446: [python] crashed when filter pyarrow.dataset on category field

lf-shaw opened a new issue #8446:
URL: https://github.com/apache/arrow/issues/8446


   I wanna filter dataset on some (pandas) category field, but python crashed.  Some sample code as follows
   ```python
   import pandas as pd
   
   import pyarrow as pa
   import pyarrow.parquet as pq
   import pyarrow.dataset as ds
   
   # B is category
   df = pd.DataFrame({'A': range(4), 'B': list('bccd')})
   df['B'] = df['B'].astype('category')
   
   # save to parquet file
   table = pa.Table.from_pandas(df)
   pq.write_table(table, 'test.parquet')
   
   # read with dataset
   dataset = ds.dataset('test.parquet')
   
   # it's ok
   dataset.to_table().to_pandas()
   
   # it's ok
   dataset.to_table(filter=ds.field('A') > 2).to_pandas()
   
   # it crashed
   dataset.to_table(filter=ds.field('B') == 'b').to_pandas()
   ```
   the crash message
   
   ```sh
   ValueOrDie called on an error: Type error: Cannot compare scalars of differing type: dictionary<values=string, indices=int32, ordered=0> vs string
   ```
   
   I know in C++ `arrow::DictionaryArray` of course cannot comapre with string. But I wanna know is there any possible to filter on category field in python?
   
   Thanks for your attention, and Thanks for this brilliant lib.


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[GitHub] [arrow] lf-shaw closed issue #8446: [python] crashed when filter pyarrow.dataset on category field

Posted by GitBox <gi...@apache.org>.
lf-shaw closed issue #8446:
URL: https://github.com/apache/arrow/issues/8446


   


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[GitHub] [arrow] lf-shaw commented on issue #8446: [python] crashed when filter pyarrow.dataset on category field

Posted by GitBox <gi...@apache.org>.
lf-shaw commented on issue #8446:
URL: https://github.com/apache/arrow/issues/8446#issuecomment-707394377


   It's cool! 
   Thanks again.


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[GitHub] [arrow] jorisvandenbossche commented on issue #8446: [python] crashed when filter pyarrow.dataset on category field

Posted by GitBox <gi...@apache.org>.
jorisvandenbossche commented on issue #8446:
URL: https://github.com/apache/arrow/issues/8446#issuecomment-707232146


   @lf-shaw yes, this is a known bug with the current dataset implementation. But it has been fixed in the meantime (https://issues.apache.org/jira/browse/ARROW-10008), and the above code snippet works on master / will work in pyarrow 2.0 (to be released in a few days)


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