rubenada commented on a change in pull request #1918:
URL: https://github.com/apache/calcite/pull/1918#discussion_r417877427
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File path: core/src/main/java/org/apache/calcite/rel/rules/PruneEmptyRules.java
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@@ -277,7 +278,11 @@ private static boolean isEmpty(RelNode node) {
if (sort.fetch != null
&& !(sort.fetch instanceof RexDynamicParam)
&& RexLiteral.intValue(sort.fetch) == 0) {
- call.transformTo(call.builder().push(sort).empty().build());
+ RelNode emptyValues = call.builder().push(sort).empty().build();
+ emptyValues = emptyValues.copy(
+ emptyValues.getTraitSet().replace(sort.getCollation()),
+ Collections.emptyList());
Review comment:
The (non propagation of) Collation trait is the root cause of this
issue. So propagating just the Collation seems the easiest way to fix this bug
(but arguably maybe not the "most correct" one).
Previously, I tried to propagate other traits as well, but it did not work
as expected:
_Propagating all traits does not seem a good solution. [...] there are some
tests failing because of the following scenario: we have an enumerable single
rel + logical empty values, so we replace the whole thing with an empty values
(which in our case is a LogicalValues, as returned by RelBuilder#empty). If we
try to propagate all traits it will fail, because we would be trying to
propagate the EnumerableConvention towards a LogicalValues. So what should be
our strategy here? Should we propagate all traits except the convention? Am I
missing something in the trait propagation process?_
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