[jira] [Commented] (CALCITE-4388) RexNode#isAlwaysFalse and isAlwaysTrue should be aligned with RexSimplify#isSafeExpression

["Zoltan Haindrich (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/CALCITE-4388?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17228429#comment-17228429 ] 

Zoltan Haindrich commented on CALCITE-4388:
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[~vladimirsitnikov] thank you for pinging me; this issue reminds me of an idea I was thinking about around I've done "saferexvisitor" stuff.

We've defined a few properties for "all" the SqlKind-s in Calcite  (we have Strong and Safe - but there might be others).
However - how the actual checkers for these properties are in different files from the "Kind"-s. So if someone adds a new kind it will fall into the "default" handler in these property checker implementations.
Adding a few annotations to SqlKind could enable us to decide these properties at the time the new kind is introduced - (and probably cover things better by answering basic questions one-by-one centered around the kind - and not around the question itself).

I would categorize "isAlwaysTrue" also a property.

I would like to note one more thing: isAlwaysTrue / safe expression check and all these things could become costly - because they are walking the rex tree thru the stack...one way around this could be to add something to each rexnode which could "cache" the computed properties of the node; or pass around some entity which could take care of caching stuff

> RexNode#isAlwaysFalse and isAlwaysTrue should be aligned with RexSimplify#isSafeExpression
> ------------------------------------------------------------------------------------------
>
>                 Key: CALCITE-4388
>                 URL: https://issues.apache.org/jira/browse/CALCITE-4388
>             Project: Calcite
>          Issue Type: Bug
>          Components: core
>    Affects Versions: 1.26.0
>            Reporter: Vladimir Sitnikov
>            Priority: Major
>
> {{(1/0) IS NULL}} should not result in {{isAlwaysFalse}}.
> Currently, {{RexSimplify}} knows that 1/0 must not be simplified, however, {{isAlwaysTrue}} and {{isAlwaysFalse}} are still wrong.
> That might result in wrong data, especially when the client code calls {{isAlways...}}
> [~kgyrtkirk], I see you contributed a lot to simplification and {{SafeRexVisitor}}. Are you interested in improving {{isAlways...}}?



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