[GitHub] [calcite] libenchao commented on a diff in pull request #2911: [CALCITE-5127] Error when executing query with subquery in select lis…

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libenchao commented on code in PR #2911:
URL: https://github.com/apache/calcite/pull/2911#discussion_r974896291


##########
core/src/main/java/org/apache/calcite/sql2rel/RelFieldTrimmer.java:
##########
@@ -481,6 +481,18 @@ public TrimResult trimFields(
     final int fieldCount = rowType.getFieldCount();
     final RelNode input = project.getInput();
 
+    boolean containsSubQuery = false;
+    for (RexNode node : project.getProjects()) {
+      if (RexUtil.containsSubQuery(node)) {
+        containsSubQuery = true;
+        break;
+      }
+    }
+    // Do not trim Project's fields before SubQueryRemoveRule applies.
+    if (containsSubQuery) {
+      return result(project, Mappings.createIdentity(fieldCount));
+    }
+

Review Comment:
   The test added in `sub-query.iq` will fail without this change. It surprised me too that this does not affect any existing plan tests. I guess that's because we don't have enough plan tests for sub query. If there is a test case which is affected by this change, then it was already wrong.
   
   Due to the integrity of this issue I think this is ok to keep it in the same PR, WDYT?



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