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https://issues.apache.org/jira/browse/CALCITE-7438?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18064034#comment-18064034
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Zhen Chen commented on CALCITE-7438:
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I think you could look into whether NULLIF is merely a syntactic sugar, i.e.,
whether Calcite has actually implemented a physical execution for NULLIF. If
that’s the case, then Calcite should probably disable that transformation for
now. If my guess is correct, I think you could contribute a physical execution
implementation for NULLIF and then prohibit this transformation.
> The nullif function stops optimizing to case when
> -------------------------------------------------
>
> Key: CALCITE-7438
> URL: https://issues.apache.org/jira/browse/CALCITE-7438
> Project: Calcite
> Issue Type: Improvement
> Components: core
> Affects Versions: 1.41.0
> Reporter: terran2010
> Priority: Major
>
> When execute sql：
> {code:java}
> select NULLIF(count(brand_name),1) from product{code}
> Calcite will make the following optimizations:
> {code:java}
> SELECT CASE WHEN COUNT(brand_name) = 1 THEN NULL ELSE COUNT(brand_name) END
> FROM foodmart.product{code}
> During the actual execution of the above SQL, COUNT (brandname) will be
> executed twice. Can we consider disabling this optimization
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