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https://issues.apache.org/jira/browse/CALCITE-482?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16908687#comment-16908687
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Haisheng Yuan commented on CALCITE-482:
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I think query hints can also do the same work with table hints. [~danny0405] Do
you have any design doc or draft? What is the usage for Project operator to use
hint? Hint has several types: scan method, join method , join ordering,
variable setting, index scan method etc.. Every hint type may have multiple
hint items, e.g. we want to specify join method by USE_HASH_JOIN,
USE_MERGE_JOIN, NO_MAPJOIN... Every hint item may need to be handled
specifically. We need to make the hint framework extensible so that other
system can create their own hint type or items, and their handlers.
> 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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