[jira] [Created] (CALCITE-2064) Allow a Convention to declare which sub-classes of RelNode it handles

[Julian Hyde (JIRA)]

Julian Hyde created CALCITE-2064:
------------------------------------

             Summary: Allow a Convention to declare which sub-classes of 
RelNode it handles
                 Key: CALCITE-2064
                 URL: https://issues.apache.org/jira/browse/CALCITE-2064
             Project: Calcite
          Issue Type: Bug
            Reporter: Julian Hyde
            Assignee: Julian Hyde


Extend {{interface Convention}} so that a convention can declare which 
sub-classes of RelNode it uses. The method is as follows:

{code}
interface Convention {
  <R extends RelNode>
 Pair<Class<? extends R>, RelFactory<R>> getRelClass(Class<R> clazz);
}

interface RelFactory<R extends RelNode> {
  RelNode copy(R r);
}

interface FilterFactory extends RelFactory<Filter> {
   RelNode createFilter(RelNode input, RexNode condition);
}
{code}

For example, {{FooConvention}} might have classes {{FooFilter}} and 
{{FooProject}}.
So, {{fooConvention.getRelClass(Filter.class)}} would return a pair, 
{{(FooFilter.class, new FooFilterFactory())}}.

This is a step towards self-describing conventions. A convention could, for 
example, walk over a tree of logical RelNodes and transcribe them all to its 
own sub-class of RelNode. And we could have a RelBuilder produce RelNodes to 
match a particular convention (emulating what is currently done using 
RelNode.copy).



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