[jira] [Commented] (CALCITE-7044) Add internal operator NOT NULL to enhance rewrite COALESCE operator

["xiong duan (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/CALCITE-7044?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17956226#comment-17956226 ] 

xiong duan commented on CALCITE-7044:
-------------------------------------

Fixed in [12e7d62|https://github.com/apache/calcite/commit/12e7d621bbb19aa32cb45329cb84532115037b7a]. Thanks for the review [~mbudiu] and [~zabetak] .

> Add internal operator NOT NULL to enhance rewrite COALESCE operator
> -------------------------------------------------------------------
>
>                 Key: CALCITE-7044
>                 URL: https://issues.apache.org/jira/browse/CALCITE-7044
>             Project: Calcite
>          Issue Type: Bug
>            Reporter: xiong duan
>            Priority: Major
>              Labels: pull-request-available
>
> Add internal operator NOT NULL to enhance rewrite COALESCE operator.
> This issue originated from the discussion of CALCITE-6978. 
> A new NOT NULL internal operator was added, indicating that this expression will never be NULL. 
> The expression coalesce(a,b) can be transformed into CASE WHEN a is not null THEN NOT NULL(a) ELSE b
> 1) `not null` operator doesn't do anything, just tell the validator this filed is not null.
> 2) When we do RelToSQL, we can ignore it directly. 
> Notice:If the query contains nondeterministic function calls, like RANDOM. Duplicating such will produce different results, 



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