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https://issues.apache.org/jira/browse/CALCITE-2620?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16649717#comment-16649717
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zhen wang commented on CALCITE-2620:
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[~pzw2018] while this optimization surely looks reasonable, can I ask under
what circumstances would people/software write such an expression ?
> Simplify "coalesce(null,x)" to "x"
> ----------------------------------
>
> Key: CALCITE-2620
> URL: https://issues.apache.org/jira/browse/CALCITE-2620
> Project: Calcite
> Issue Type: Improvement
> Components: core
> Affects Versions: 1.18.0
> Reporter: pengzhiwei
> Assignee: Julian Hyde
> Priority: Major
>
> "coalesce(x0,x1,.....)" can be simplified if any of "xi" is null literal.
> e.g. "coalesce(null,x)" can simplify to "x", "coalesce(x,null,y)" can
> simplify to "coalesce(x,y)"
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