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https://issues.apache.org/jira/browse/CALCITE-6550?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17877442#comment-17877442
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Caican Cai commented on CALCITE-6550:
-------------------------------------
There is another issue to consider here. If the SqlStdOperatorTable is already
being adapted, then SqlLibraryOperators does not seem to take effect.
> Improve SQL function overloading
> --------------------------------
>
> Key: CALCITE-6550
> URL: https://issues.apache.org/jira/browse/CALCITE-6550
> Project: Calcite
> Issue Type: Improvement
> Components: core
> Reporter: Norman Jordan
> Assignee: Norman Jordan
> Priority: Minor
>
> All SQL functions across all SQL libraries as well as the standard functions
> are used as keys in a Map (in the class {*}RexImpTable{*}). The hashcode and
> equals methods currently only look at the name, kind and class.
> [https://github.com/apache/calcite/blob/main/core/src/main/java/org/apache/calcite/sql/SqlOperator.java#L424]
> [https://github.com/apache/calcite/blob/main/core/src/main/java/org/apache/calcite/sql/SqlOperator.java#L439]
> This causes a few problems:
> * Some functions may have the same name and kind but different sets of
> parameters
> * Two different SQL libraries may have functions with the same name and kind
> (and even parameters) but have different implementations.
> The current work around is to create new anonymous classes when needed to
> avoid collisions in the Map. Here is an example.
> https://github.com/apache/calcite/blob/main/core/src/main/java/org/apache/calcite/sql/fun/SqlLibraryOperators.java#L578
> The hashcode and equals methods should consider more information, such as the
> parameters as well as some way to differentiate similar functions in
> different libraries.
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