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https://issues.apache.org/jira/browse/CALCITE-3541?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Stamatis Zampetakis reassigned CALCITE-3541:
--------------------------------------------

    Assignee:     (was: Stamatis Zampetakis)

> Avoid transformations to Enumerable nodes for custom SqlOperators
> -----------------------------------------------------------------
>
>                 Key: CALCITE-3541
>                 URL: https://issues.apache.org/jira/browse/CALCITE-3541
>             Project: Calcite
>          Issue Type: Improvement
>          Components: core
>    Affects Versions: 1.21.0
>            Reporter: Stamatis Zampetakis
>            Priority: Major
>
> Most Enumerable converter rules apply a transformation as soon as the 
> {{RelNode}} class and its convention match those defined by the rule. 
> However, there are use-cases that we would like to restrict the matches even 
> further to avoid generating unimplementable plans that will fail at runtime. 
> The most prominent example comes from extending the standard operator set 
> with new {{SqlOperator}} s that appear in filters and projections as part of 
> a row expression ({{RexNode}}). If we use the default instance of the 
> {{EnumerableCalcRule}} we might end-up with a plan that will fail at runtime 
> since the new operator is not handled by the Enumerable convention. Most 
> likely there is a {{RelNode}} in another convention that can handle this new 
> operator. 
> We could avoid such undesirable transformations by allowing instantiations of 
> the Enumerable converter rules with user-defined predicates. This also means 
> adding public constructors to the rules that currently they do not have one.



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