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https://issues.apache.org/jira/browse/CALCITE-2438?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16571184#comment-16571184
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Vladimir Sitnikov commented on CALCITE-2438:
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[~julianhyde], I would like to update {{RexSimplify}} as follows:
1) Avoid multiple passes over the same expressions. Current logic calls
"simplify" in multiple places, and it might cause simplification of the same
tree again and again.
2) I would like to rework {{unknownAsFalse}} into support for {{IS TRUE}}.
Current support for {{unknownAsFalse}} is hard to follow, and it looks like
IS_TRUE(expr) allows for the same optimizations. In other words,
"unknownAsFalse" would become a silent adding of IS_TRUE on top of the input
expression. Then rules like {{OR(x, y) IS TRUE ==> x IS TRUE or y IS TRUE}}
would push {{IS TRUE}} downstream.
3) I would like to "reorder" predicates in a defined order (e.g. rewrite {{5=x
==> x=5}} or {{(x=1 or y=2) and (z=3)}} ==> {{(z=3) and (x=1 or y=2)}}. It
looks like adding {{int nodeCount;}} to {{RexNode}} would be helpful to rank
rex nodes.
4) There are other bugs identified by expression fuzzer (like
https://github.com/apache/calcite/pull/776/commits/980f491323fcf61f5c966120870b3442cae41c23
or
https://github.com/apache/calcite/pull/776/commits/f2fba02f02cfa6b094e67e37da6be2ee19861276
), so it does not make much sense in committing {{isAlwaysTrue}} only.
We are not in rush for releasing Calcite to fix RexCall#isAlwaysTrue, aren't
we? So I think we have time to evaluate improved RexSimplify.
> RexCall#isAlwaysTrue return incorrect result
> ---------------------------------------------
>
> Key: CALCITE-2438
> URL: https://issues.apache.org/jira/browse/CALCITE-2438
> Project: Calcite
> Issue Type: Bug
> Components: core
> Affects Versions: 1.17.0
> Reporter: pengzhiwei
> Assignee: Julian Hyde
> Priority: Critical
> Attachments: 屏幕快照 2018-08-02 下午7.26.20.png, 屏幕快照 2018-08-02
> 下午7.34.26.png
>
>
> In the expression as followed:
> {code:java}
> ((sal IS NULL) IS NOT NULL) IS FALSE
> {code}
> The RexCall#isAlwaysTrue return true,however the correct answer is false.
> I find the reason is that there is a wrong logic in the isAlwaysTrue,when
> getKind() is IS_NOT_FALSE、IS_FALSE and IS_NOT_FALSE :
> !屏幕快照 2018-08-02 下午7.34.26.png!
> Can you have a check for me,thanks!
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