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https://issues.apache.org/jira/browse/CALCITE-482?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16902331#comment-16902331
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Haisheng Yuan commented on CALCITE-482:
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For hints like {{selectivity}}, a good place to put is the MEMO group, instead
of the operator, as long as they are in the same MEMO group, they can share the
same property.
> Implement sql and planner hints
> -------------------------------
>
> Key: CALCITE-482
> URL: https://issues.apache.org/jira/browse/CALCITE-482
> Project: Calcite
> Issue Type: Bug
> Affects Versions: 1.0.0-incubating
> Reporter: Vladimir Sitnikov
> Assignee: Danny Chan
> Priority: Major
> Labels: pull-request-available
> Time Spent: 2h
> Remaining Estimate: 0h
>
> Query optimizer can never be perfect, so it makes sense to implement hints to
> allow user better control the execution.
> For instance: "never merge this subquery with others" (`/+ no_merge/`),
> "treat those tables as leading ones" (`/*+ leading */`), etc.
> Hints would enable predictable performance and the planning time would be
> improved as well.
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