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https://issues.apache.org/jira/browse/CALCITE-7145?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18035663#comment-18035663
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Stamatis Zampetakis commented on CALCITE-7145:
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[~thomas.rebele] I like the idea of improving safety by checking for "special"
arguments/literals although I am not sure if the added complexity/risk is worth
the effort. I will review the new PR and will post further comments there.
Currently, IS NULL(+(null, CAST($0):INTEGER)) is simplified to true but this is
a wrong simplification for the standard unsafe cast and shouldn't happen in the
first place. Since Druid at the moment uses the standard CAST I would say that
the new plan is the expected one. In fact, I would go even further and say that
pushing a regular CAST to Druid is incorrect since the semantics are different.
Anyways, I feel that this is a separate issue thus I logged CALCITE-7271
although I wouldn't rush fixing it since it seems a rather minor edge case.
[~julianhyde] Having a new sequence operator for simplifying unsafe operations
is a nice idea. I will keep it in mind for the future if we find that it's
really beneficial/important to perform such simplifications.
After checking a bit more the code around the simplification of IS [NOT] NULL I
found that the problem reported here is roughly the same to CALCITE-2929 and
CALCITE-3457 but for different operators. The solution that was adopted back
then was to consider that the operators (CAST, ITEM) have [special nullability
semantics|https://github.com/apache/calcite/blob/8b5c17e51e0c9c3f8e3db17c8d449e67e4e2974a/core/src/main/java/org/apache/calcite/rex/RexSimplify.java#L1279].
For this reason, the simplification bails out when it encounters CAST and
ITEM. I am highlighting this now since we may want to revisit this part of the
code in a follow-up for making the handling more uniform.
> RexSimplify should not simplify IS NULL(10/0)
> ---------------------------------------------
>
> Key: CALCITE-7145
> URL: https://issues.apache.org/jira/browse/CALCITE-7145
> Project: Calcite
> Issue Type: Bug
> Reporter: Thomas Rebele
> Assignee: Thomas Rebele
> Priority: Major
> Labels: pull-request-available
>
> RexSimplify incorrectly simplifies {{IS NULL(10/0)}} to false and {{IS NOT
> NULL(10,0)}} to true
> In other DBMS it's either the inverse (sqlite, MySQL, MariaDB), or they throw
> an exception in both cases (Oracle, Postgres). The behavior was also
> mentioned in a comment on CALCITE-3368.
> Is it right that throwing an exception during query execution is the expected
> behavior according to the SQL standard?
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