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https://issues.apache.org/jira/browse/CALCITE-482?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17014869#comment-17014869
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Danny Chen commented on CALCITE-482:
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bq. Now you add BiFunction<RelNode, RelNode, RelNode> handler function that
applies to one of the arguments only, and it completely ignores Map<RelNode,
RelNode>
bq.
bq. That does not sound right.
Why do you think we should take the map into account, i have no idea whether
the root node hints should copy to that, i only saw one invocation for
{code:java}
RelOptRuleCall#transformTo(RelNode rel, Map<RelNode, RelNode> equiv)
{code}
in SortProjectTransposeRule, and for that case, we should not copy the hints.
bq. Re BiFunction. Have you considered creating a named interface to express
the meaning of the parameter?
bq. Frankly speaking, BiFunction<RelNode, RelNode, RelNode> handler is really
confusing (both interface naming and parameter naming).
I kind of agree, would fire a fix if i have time.
> Implement SQL and planner hints
> -------------------------------
>
> Key: CALCITE-482
> URL: https://issues.apache.org/jira/browse/CALCITE-482
> Project: Calcite
> Issue Type: Improvement
> Components: core
> Affects Versions: 1.21.0
> Reporter: Vladimir Sitnikov
> Assignee: Danny Chen
> Priority: Major
> Labels: pull-request-available
> Fix For: 1.22.0
>
> Time Spent: 8h 10m
> 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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