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https://issues.apache.org/jira/browse/CALCITE-2247?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16469157#comment-16469157
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Zoltan Haindrich commented on CALCITE-2247:
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[~julianhyde] I've missed that - I was clearly not thinking in 3 valued logic
correctly.
Currently (b=1 OR b!=1) is simplified to (b=1 OR b is not null) which is
somewhat ok; better would be to simplify that to (b is not null) but I haven't
figured out how to do that without doing another pass...I will keep thinking
about it...I've updated the PR with the fix ; and some minor unknown related
changes.
There was one
[test|https://github.com/apache/calcite/pull/688/commits/438f90eed88831abe32909ad93abbd7c678cb88f#diff-9f6a8f13d9ad70d7336340bf6b2e7b71R415]
in which I think the removal of null was inappropriate; because having a
{{null}} in an OR limits its output to be only unknown or true; but never
false. Let me know if I'm wrong!
> Add rule to push in condition condition into a related disjunctive expression
> -----------------------------------------------------------------------------
>
> Key: CALCITE-2247
> URL: https://issues.apache.org/jira/browse/CALCITE-2247
> Project: Calcite
> Issue Type: Improvement
> Reporter: Zoltan Haindrich
> Assignee: Zoltan Haindrich
> Priority: Major
>
> Simplify expressions like: {code}a = 1 AND (a = 1 OR a = 2){code} to {code}a
> = 1{code}
> Conditions to apply will be:
> * in an AND condition there exists a comparison(c) and an OR (o)
> * o and c only reference 1 variable
> See HIVE-19097 for more info.
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