amaliujia commented on a change in pull request #2011:
URL: https://github.com/apache/calcite/pull/2011#discussion_r437592439
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File path: core/src/main/java/org/apache/calcite/plan/RelOptUtil.java
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@@ -3766,6 +3771,104 @@ private static void fix(List<RexNode> operands, int
before, int after) {
}
}
+ /**
+ * Determine whether there is mapping between project input and output
fields.
+ * Bail out if sort relies on non-trivial expressions.
+ */
+ private static boolean isCollationOnTrivialExpr(
+ List<RexNode> projects, RelDataTypeFactory typeFactory,
+ Mappings.TargetMapping map, RelFieldCollation fc, boolean passDown) {
+ final int index = fc.getFieldIndex();
+ int target = map.getTargetOpt(index);
+ if (target < 0) {
+ return false;
+ }
+
+ final RexNode node = passDown ? projects.get(index) : projects.get(target);
+ if (node.isA(SqlKind.CAST)) {
+ // Check whether it is a monotonic preserving cast
+ final RexCall cast = (RexCall) node;
+ RelFieldCollation newFc = Objects.requireNonNull(RexUtil.apply(map, fc));
+ final RexCallBinding binding =
+ RexCallBinding.create(typeFactory, cast,
+ ImmutableList.of(RelCollations.of(newFc)));
+ if (cast.getOperator().getMonotonicity(binding)
+ == SqlMonotonicity.NOT_MONOTONIC) {
+ return false;
+ }
+ }
+
+ return true;
+ }
+
+ public static Pair<RelTraitSet, List<RelTraitSet>> passThroughTraits(
Review comment:
Depends on if we want move all most all the code to RelOptUtil, I feel
like only `isCollationOnTrivialExpr` can be moved to RelOptUtil.
At least `RelOptUtil.passThroughTraits` and `RelOptTuil. deriveTraits`,
seems to me, could encourage people write all `passThroughTraits` and
`deriveTraits` into `RelOptUtil`, because names here are too generic.
For example, I might ask, why not move implementations in Enumerable Joins
to `RelOptUtil`, etc. And will they become a part of
`RelOptUtil.passThroughTraits` and `RelOptTuil. deriveTraits`?
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