[jira] [Created] (ARROW-6625) Allow concat_tables to null or default fill missing columns

["Daniel Nugent (Jira)" <ji...@apache.org>]

Daniel Nugent created ARROW-6625:
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             Summary: Allow concat_tables to null or default fill missing columns
                 Key: ARROW-6625
                 URL: https://issues.apache.org/jira/browse/ARROW-6625
             Project: Apache Arrow
          Issue Type: Wish
          Components: Python
            Reporter: Daniel Nugent


The concat_tables function currently requires schemas to be identical across all tables to be concat'ed together. However, tables occasionally are conforming on type where present, but a column will be absent.

In this case, allowing for null filling (or default filling) would be ideal.

I imagine this feature would be an optional parameter on the concat_tables function. Presumably the argument could be either a boolean in the case of blanket null filling, or a mapping type for default filling. If a user wanted to default fill some columns, but null fill others, they could use a None as the value (defaultdict would make it simple to provide a blanket null fill if only a few default value columns were desired).

If a mapping wasn't present, the function should probably raise an error.

The default behavior would be the current and thus the default value of the parameter should be False or None.



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