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https://issues.apache.org/jira/browse/CALCITE-7044?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17954497#comment-17954497
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Stamatis Zampetakis commented on CALCITE-7044:
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I don't have all the details on why we need a new internal operator but if the
latter remains in the plan its gonna be a noticeable breaking change for many
projects caused they will be forced to handle it somehow. Let's weight the pros
and cons carefully before proceeding with this change.
> 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
>
> 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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