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