[GitHub] [calcite] chunweilei commented on a change in pull request #1987: [CALCITE-4020] Support Calc operator in RelFieldTrimmer

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

chunweilei commented on a change in pull request #1987:
URL: https://github.com/apache/calcite/pull/1987#discussion_r439907127



##########
File path: core/src/main/java/org/apache/calcite/sql2rel/RelFieldTrimmer.java
##########
@@ -350,6 +354,92 @@ public TrimResult trimFields(
         Mappings.createIdentity(rel.getRowType().getFieldCount()));
   }
 
+  /**
+   * Variant of {@link #trimFields(RelNode, ImmutableBitSet, Set)} for
+   * {@link org.apache.calcite.rel.logical.LogicalCalc}.
+   */
+  public TrimResult trimFields(
+      Calc calc,
+      ImmutableBitSet fieldsUsed,
+      Set<RelDataTypeField> extraFields) {
+    final RexProgram rexProgram = calc.getProgram();
+    final List<RexNode> projs = Lists.transform(rexProgram.getProjectList(),
+        rexProgram::expandLocalRef);
+
+    final RelDataType rowType = calc.getRowType();
+    final int fieldCount = rowType.getFieldCount();
+    final RelNode input = calc.getInput();
+
+    final Set<RelDataTypeField> inputExtraFields =
+        new LinkedHashSet<>(extraFields);
+    RelOptUtil.InputFinder inputFinder =

Review comment:
       Do we have to use `LinkedHashSet `? Looks like `HashSet` is enough.




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