[jira] [Commented] (CALCITE-482) Implement SQL and planner hints

["Vladimir Sitnikov (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/CALCITE-482?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17014265#comment-17014265 ] 

Vladimir Sitnikov commented on CALCITE-482:
-------------------------------------------

[~danny0405], thanks for the feature, however it looks like RelOptRuleCall#transformTo needs adjustments.

{noformat}
  public abstract void transformTo(RelNode rel,
      Map<RelNode, RelNode> equiv,
      BiFunction<RelNode, RelNode, RelNode> handler);
{noformat}

In practice, the hints are not applied to {{Map<RelNode, RelNode> equiv}}
Was it intentional?
Why is it like that?

> 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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