[jira] [Created] (ARROW-991) [Python] PyArray_SimpleNew should not be used with NPY_DATETIME

["Wes McKinney (JIRA)" <ji...@apache.org>]

Wes McKinney created ARROW-991:
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             Summary: [Python] PyArray_SimpleNew should not be used with NPY_DATETIME
                 Key: ARROW-991
                 URL: https://issues.apache.org/jira/browse/ARROW-991
             Project: Apache Arrow
          Issue Type: Bug
          Components: Python
    Affects Versions: 0.3.0
            Reporter: Wes McKinney
            Assignee: Wes McKinney
            Priority: Critical
             Fix For: 0.4.0


From a non-deterministic test failure in pandas reported to me by [~jreback], I see that {{PyArray_SimpleNew}} calls {{PyArray_DescrFromType}}, which return a reference to a cached dtype: https://github.com/numpy/numpy/blob/1d592c12ca7f9c7f471aa8d20b538c5cb4f2cdce/numpy/core/src/multiarray/arraytypes.c.src#L4403. Since we expect to be able to mutate a datetime64 dtype in libarrow_python, this can cause failures in other code when uses a dtype that we have accidentally mutated internally.

Luckily we are only modifying dtype metadata in a couple of places so this should not be too invasive to fix: https://github.com/apache/arrow/blob/master/cpp/src/arrow/python/pandas_convert.cc#L1995



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