[GitHub] [calcite] hsyuan commented on a change in pull request #2011: [CALCITE-4016] Support trait propagation for EnumerableCalc

[GitBox <gi...@apache.org>]

hsyuan commented on a change in pull request #2011:
URL: https://github.com/apache/calcite/pull/2011#discussion_r437658417



##########
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:
       I had the same feeling. How about add a package level internal interface for EnumerableProject and EnumerableCalc with default implementation so that both operators just need to implement the interface?




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