jhorstmann commented on pull request #9038:
URL: https://github.com/apache/arrow/pull/9038#issuecomment-753397568
Semantics for the `IN` and `OR` versions should be the same *in SQL*, for
example [try the following query in postgres][1]:
```
SELECT 'abc' in ('abc', 'def')
, 'abc' in ('abc', 'def', null)
, 'abc' in ('def', null)
, null in ('abc', 'def')
-- same expressions rewritten using OR
, (('abc' = 'abc') OR ('abc' = 'def'))
, (('abc' = 'abc') OR ('abc' = 'def') or ('abc' = null))
, (('abc' = 'def') or ('abc' = null))
, ((null = 'abc') OR (null = 'def'))
```
1. result is `true`, no nulls involved
2. result is `true`, additional `null` on the rhs does not change this
since `(true OR null) = true`
3. result is `null` since `(false OR null) IS NULL`
4. result is `null` since lhs of each comparison is null
But you are right, it's not that simple since the arrow `or` / `and` kernels
currently do not follow this sql behaviour. We might want to change that or
rather introduce separate boolean kernels with the sql behaviour regarding
nulls.
[1]: http://sqlfiddle.com/#!17/9eecb/67863
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