[jira] [Commented] (CALCITE-601) Meta.CursorFactory#deduce should not try to check column count

["Julian Hyde (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/CALCITE-601?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14326639#comment-14326639 ] 

Julian Hyde commented on CALCITE-601:
-------------------------------------

It sounds like you're right, and if so, I will hit this as I work through the issues as I try to set ENABLE_BINDABLE = true.

Note that I have extended interface Bindable: sub-interface ArrayBindable guarantees to return Object[]s (and its getElementType() method always returns Object[].class). A BindableRel (i.e. a RelNode of BINDABLE convention) implements ArrayBindable, and therefore commits to returning Objects[] however many columns it has.

The interface Bindable is of course used in other places than BINDABLE convention, but this at least simplifies BINDABLE convention. 

> Meta.CursorFactory#deduce should not try to check column count
> --------------------------------------------------------------
>
>                 Key: CALCITE-601
>                 URL: https://issues.apache.org/jira/browse/CALCITE-601
>             Project: Calcite
>          Issue Type: Bug
>    Affects Versions: 1.0.0-incubating
>            Reporter: Vladimir Sitnikov
>            Assignee: Julian Hyde
>
> Current implementation of {{Meta.CursorFactory#deduce}} thinks that Enumerable with single column cannot be {{Object\[\]}} wrapped.
> This sounds like an extreme high coupling.
> I think it makes sense if "Bindable" would provide its {{JavaRowFormat}} along with "ElementType".
> I think it makes sense to reject non-typed, non-rowformatproviding Bindables out of Enumerable/Bindable conventions.
> {code:java}
>     public static CursorFactory deduce(List<ColumnMetaData> columns,
>         Class resultClazz) {
>       if (columns.size() == 1) {
>         return OBJECT;  // <-- !! Look here. deduce just assumes single-column results are always naked
>       } else if (resultClazz != null && !resultClazz.isArray()) {
>         return record(resultClazz);
>       } else {
>         return ARRAY;
>       }
>     }
> {code}



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