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https://issues.apache.org/jira/browse/CALCITE-5915?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17754067#comment-17754067
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Vladimir Steshin commented on CALCITE-5915:
-------------------------------------------
[~shenlang], thank you. I've realized what's going on. We use
{code:java}
CoreRules.FILTER_SUB_QUERY_TO_CORRELATE,
CoreRules.PROJECT_SUB_QUERY_TO_CORRELATE,
CoreRules.JOIN_SUB_QUERY_TO_CORRELATE
{code}
but we have no call of _RelDecorrelator#decorrelateQuery_. And the subquery
transformation omits hints propagation:
{code:java}
public static RelNode RelOptUtil#propagateRelHints(RelNode originalRel, RelNode
equiv) {
if (!(originalRel instanceof Hintable)
|| ((Hintable) originalRel).getHints().size() == 0) {
// Exists here.
return equiv;
}
...
}
{code}
This happens because after the subqueries change hints appear below this code's
_RelNode originalRel_. It has no hints, the propagation stops. Example:
{code:java}
LogicalProject
LogicalFilter (had no hints, *propagateRelHints(RelNode, RelNode) exists*)
LogicalJoin
left: TableScan
right: LogicalAggregate
LogicalProject (has *hints to propagate* down)
LogicalFilter
LogicalTableScan (*waits for the hints*)
{code}
To me it is a bit weird that the propagation checks current node's hints and
exists. Hints might be extracted further. Well, I just call
_propagateRelHints(RelNode, boolean)_ after that rule set. Works.
> Missing SQL hints in not-expanded subqueries.
> ----------------------------------------------
>
> Key: CALCITE-5915
> URL: https://issues.apache.org/jira/browse/CALCITE-5915
> Project: Calcite
> Issue Type: Bug
> Reporter: Vladimir Steshin
> Priority: Minor
> Attachments: SqlHintsInSubqueriesWithDisabledExpanding.java,
> image-2023-08-13-23-11-56-589.png
>
>
> Not sure if it is a bug becuase the query plans in this case might not be
> final and require further expanding, but the SQL hints might not be
> propagated to subqueries when SqlToRelConverter#withExpand==false. This
> happens because hints are pushed down with
> _RelOptUtil#RelHintPropagateShuttle_ and
> _RelOptUtil#SubTreeHintPropagateShuttle_ which travese through
> _RelNode#getInputs()_. But what if node is not accessible as other node’s
> input like keeping in _LogicalFilter#condition_? Then the shuttles skip such
> nodes.
> Test attached.
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