ARROW-6339: [Python][C++] Rowgroup statistics for pd.NaT array ill defined #5180
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Can you open a JIRA issue? |
fjetter
changed the title
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@ursabot build |
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@fjetter this gives a bunch of statistics-related failures in the tests. It seems that the |
wesm
reviewed
Sep 15, 2019
| @@ -623,6 +623,11 @@ bool ApplicationVersion::HasCorrectStatistics(Type::type col_type, | |||
| return false; | |||
| } | |||
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| // Null only arrays do not have proper statistics | |||
| if (statistics.null_count > 0 && statistics.distinct_count == 0) { | |||
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We never actually compute distinct_count so it's always going to be zero I think
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I'll try to raise an exception as was suggested by @xhochy |
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I guess the proper position for the exception would be the |
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@xhochy No idea. Can None be a regular value for those statistics? |
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For an all-null column |
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this was done in 62202ee |
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The issue is that a NaT array is not initialised as a NullArray and the statistics are not invalidated causing the ill defined behaviour.
Compared to a real NullArray (
pd.DataFrame({"t": [None]})) this gives the same behaviour, i.e. statistics return None. I'm not entirely sure if this is the intended behaviour.