xiedeyantu commented on code in PR #4745:
URL: https://github.com/apache/calcite/pull/4745#discussion_r2690580520
##########
core/src/main/java/org/apache/calcite/plan/RelTraitSet.java:
##########
@@ -389,7 +389,14 @@ public RelTraitSet getDefaultSansConvention() {
*/
@SuppressWarnings("unchecked")
public <T extends RelCollation> @Nullable T getCollation() {
- return (@Nullable T) getTrait(RelCollationTraitDef.INSTANCE);
+ RelTrait trait = getTrait(RelCollationTraitDef.INSTANCE);
+ if (trait instanceof RelCompositeTrait) {
+ // If the trait is a composite trait, we return the first one as a
+ // representative trait. If RelCompositeTrait contain [[a, b], [a]].
+ // Selects [a,b] as it implies [a]; preserves the strongest ordering.
+ return (T) ((RelCompositeTrait) trait).trait(0);
Review Comment:
In the case of `order by arr nulls last`, the following error will be
reported:
```
> java.sql.SQLException: Error while executing SQL "select * from
> (values
> (2, array[null, 3]),
> (3, array[3, 4]),
> (1, array[1, 2]),
> (4, array[4, 5]),
> (5, cast(null as integer array))) as t(id, arr)
> order by arr nulls last": class org.apache.calcite.plan.RelCompositeTrait
cannot be cast to class org.apache.calcite.rel.RelCollation
(org.apache.calcite.plan.RelCompositeTrait and
org.apache.calcite.rel.RelCollation are in unnamed module of loader 'app')
> at org.apache.calcite.avatica.Helper.createException(Helper.java:56)
> at org.apache.calcite.avatica.Helper.createException(Helper.java:41)
> at
org.apache.calcite.avatica.AvaticaStatement.executeInternal(AvaticaStatement.java:164)
> at
org.apache.calcite.avatica.AvaticaStatement.executeQuery(AvaticaStatement.java:228)
> at net.hydromatic.quidem.Quidem.checkResult(Quidem.java:317)
> at net.hydromatic.quidem.Quidem.access$2600(Quidem.java:54)
> at
net.hydromatic.quidem.Quidem$ContextImpl.checkResult(Quidem.java:1778)
> at
net.hydromatic.quidem.Quidem$CheckResultCommand.execute(Quidem.java:985)
> at
net.hydromatic.quidem.Quidem$CompositeCommand.execute(Quidem.java:1522)
> at net.hydromatic.quidem.Quidem.execute(Quidem.java:204)
> at org.apache.calcite.test.QuidemTest.checkRun(QuidemTest.java:350)
> at org.apache.calcite.test.QuidemTest.test(QuidemTest.java:532)
> at org.apache.calcite.test.CoreQuidemTest2.main(CoreQuidemTest2.java:38)
```
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