[jira] [Commented] (CALCITE-495) Support hints to be passed through select/DML commands

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

    [ https://issues.apache.org/jira/browse/CALCITE-495?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14233663#comment-14233663 ] 

Julian Hyde commented on CALCITE-495:
-------------------------------------

These examples imply that hints can only occur directly after a SELECT, UPSERT, DELETE keyword. If that is the case, it should be straightforward to attach the hints to the SqlNode (AST).

Can hints occur after SELECT in a sub-query? Are hints defined in views retained when the view is expanded into a query?

If hints defined on specific parts of a query (e.g. a join or a sub-query), as to being "global" to a query, then we would need to propagate them to the appropriate RelNode for them to have the right effect; and we would need to propagate them further each time a rule fires. That would be hard to achieve.

> Support hints to be passed through select/DML commands
> ------------------------------------------------------
>
>                 Key: CALCITE-495
>                 URL: https://issues.apache.org/jira/browse/CALCITE-495
>             Project: Calcite
>          Issue Type: Improvement
>            Reporter: James Taylor
>            Assignee: Julian Hyde
>              Labels: phoenix
>
> Hints are a useful mechanism for allowing the user to override optimizer decisions. It'd be nice if Calcite supported passing hints through in the /*+ MY_HINT MY_OTHER_HINT */ syntax. For examples, see http://phoenix.apache.org/language/index.html#select



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