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https://issues.apache.org/jira/browse/CALCITE-4055?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17130628#comment-17130628
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Ruben Q L commented on CALCITE-4055:
------------------------------------
[~danny0405], I understand. However, I think that this approach could lead to
undesired consequences in RelFieldTrimmer.
Considering we must trim an Aggregate (origAgg, with aggHint) in
{{RelFielTrimmer#trimFields(Aggregate,...)}}.
At the end of that method, we would build the new aggregate and return it:
{code}
...
relBuilder.aggregate(...);
RelNode output = relBuilder.build();
return result(output, mapping);
{code}
If just before the return we introduce:
{code}
...
RelOptUtil.copyRelHints(origAgg, output);
return result(output, mapping);
{code}
There is no guarantee that "output" is in fact an Aggregate. It could be a
non-Hintable, in which case there would be no problem, since copyRelHints will
be a NO-OP. But it could be a Project (due to RelBuilder#aggregate
implementation), which is Hintable, and in that case we would be transferring
the "aggHint" from the original Aggregate to the new Project, and I assume this
should not be the case.
> RelFieldTrimmer loses join hints
> --------------------------------
>
> Key: CALCITE-4055
> URL: https://issues.apache.org/jira/browse/CALCITE-4055
> Project: Calcite
> Issue Type: Bug
> Components: core
> Affects Versions: 1.23.0
> Reporter: Ruben Q L
> Assignee: Ruben Q L
> Priority: Major
> Labels: pull-request-available
> Time Spent: 10m
> Remaining Estimate: 0h
>
> The trimmed plan generated by RelFieldTrimmer can lose the hints that might
> be present in the input plan.
> The issue can be reproduced with the following test (to be added to
> RelFieldTrimmerTest):
> {code:java}
> @Test void testJoinWithHints() {
> final RelHint noHashJoinHint =
> RelHint.builder("NO_HASH_JOIN").inheritPath(0).build();
> final RelBuilder builder = RelBuilder.create(config().build());
> final RelNode original =
> builder.scan("EMP")
> .scan("DEPT")
> .join(JoinRelType.INNER,
> builder.equals(
> builder.field(2, 0, "DEPTNO"),
> builder.field(2, 1, "DEPTNO")))
> .hints(noHashJoinHint)
> .project(
> builder.field("ENAME"),
> builder.field("DNAME"))
> .build();
> final RelFieldTrimmer fieldTrimmer = new RelFieldTrimmer(null, builder);
> final RelNode trimmed = fieldTrimmer.trim(original);
> final String expected = ""
> + "LogicalProject(ENAME=[$1], DNAME=[$4])\n"
> + " LogicalJoin(condition=[=($2, $3)], joinType=[inner])\n"
> + " LogicalProject(EMPNO=[$0], ENAME=[$1], DEPTNO=[$7])\n"
> + " LogicalTableScan(table=[[scott, EMP]])\n"
> + " LogicalProject(DEPTNO=[$0], DNAME=[$1])\n"
> + " LogicalTableScan(table=[[scott, DEPT]])\n";
> assertThat(trimmed, hasTree(expected));
> assertTrue(original.getInput(0) instanceof Join);
> final Join originalJoin = (Join) original.getInput(0);
> assertTrue(originalJoin.getHints().contains(noHashJoinHint));
> assertTrue(trimmed.getInput(0) instanceof Join);
> final Join join = (Join) trimmed.getInput(0);
> assertTrue(join.getHints().contains(noHashJoinHint));
> }
> {code}
> which fails in the last line:
> {{assertTrue(join.getHints().contains(noHashJoinHint));}}
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