[ARROW-991] [Python] PyArray_SimpleNew should not be used with NPY_DATETIME

• Type: Bug
• Status: Resolved
• Priority: Critical
• Resolution: Fixed
• Affects Version/s: 0.3.0
• Fix Version/s: 0.4.0
• Component/s: Python
• External issue URL: https://github.com/apache/arrow/issues/16588
• Assignee: Wes McKinney
• Reporter: Wes McKinney
• Created: 09/May/17 22:47
• Updated: 11/Jan/23 07:12
• Resolved: 10/May/17 01:01

Description

From a non-deterministic test failure in pandas reported to me by Jeff Reback, I see that PyArray_SimpleNew calls PyArray_DescrFromType, which returns 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