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https://issues.apache.org/jira/browse/CALCITE-601?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14332102#comment-14332102
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Julian Hyde commented on CALCITE-601:
-------------------------------------
Bindable is not intended to allow people to plug-in external data sources, or
to transmit metadata. It is just an interface to generate code into.
"bind" isn't a perfect name, but I wanted to convey the two-step process: bind
the code to a runtime environment, then execute. In JDBC you have connect
(creates a Connection), prepare (creates a PreparedStatement), and execute
(creates a ResultSet). Imagine that you could prepare before you connect. You
would have something like a PreparedStatement that isn't associated with a
connection. "bind" is the thing that converts a connection-less prepared
statement to a PreparedStatement that is ready to execute.
> 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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