Sergey Shelukhin commented on HIVE-18622:

I finished reviewing iteration 7 and 7-to-9 diff and now my brain hurts, left 
some more comments.
I hope this is covered by tests.

> Vectorization: IF Statements, Comparisons, and more do not handle NULLs 
> correctly
> ---------------------------------------------------------------------------------
>                 Key: HIVE-18622
>                 URL: https://issues.apache.org/jira/browse/HIVE-18622
>             Project: Hive
>          Issue Type: Bug
>          Components: Hive
>            Reporter: Matt McCline
>            Assignee: Matt McCline
>            Priority: Critical
>             Fix For: 3.0.0
>         Attachments: HIVE-18622.03.patch, HIVE-18622.04.patch, 
> HIVE-18622.05.patch, HIVE-18622.06.patch, HIVE-18622.07.patch, 
> HIVE-18622.08.patch, HIVE-18622.09.patch, HIVE-18622.091.patch, 
> HIVE-18622.092.patch, HIVE-18622.093.patch, HIVE-18622.094.patch, 
> HIVE-18622.095.patch, HIVE-18622.096.patch, HIVE-18622.097.patch
>  Many vector expression classes are setting noNulls to true which does not 
> work if the VRB is a scratch column being reused. The previous use may have 
> set noNulls to false and the isNull array will have some rows marked as NULL. 
> The result is wrong query results and sometimes NPEs (for BytesColumnVector).
> So, many vector expressions need this:
> {code:java}
>       // Carefully handle NULLs...
>       /*
>        * For better performance on LONG/DOUBLE we don't want the conditional
>        * statements inside the for loop.
>        */
>       outputColVector.noNulls = false;
>  {code}
> And, vector expressions need to make sure the isNull array entry is set when 
> outputColVector.noNulls is false.
> And, all place that assign column value need to set noNulls to false when the 
> value is NULL.
> Almost all cases where noNulls is set to true are incorrect.

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