[GitHub] [calcite] libenchao commented on a diff in pull request #3085: [CALCITE-5530] RelToSqlConverter[ORDER BY] generates an incorrect fie…

["libenchao (via GitHub)" <gi...@apache.org>]

libenchao commented on code in PR #3085:
URL: https://github.com/apache/calcite/pull/3085#discussion_r1181247359


##########
core/src/main/java/org/apache/calcite/rel/rel2sql/SqlImplementor.java:
##########
@@ -1791,6 +1791,14 @@ private boolean needNewSubQuery(
         return false;
       }
       final Clause maxClause = Collections.max(clauses);
+
+      if (rel instanceof Project
+          && clauses.contains(Clause.ORDER_BY)
+          && dialect.getConformance().isSortByOrdinal()) {
+        // Cannot merge a Project that contains sort by ordinal under it.
+        return hasSortByOrdinal();

Review Comment:
   To be honest, I felt uneasy about moving this up. I'm not sure if we will miss some opportunity to add a new sub query. The changes in https://github.com/apache/calcite/pull/3057 was also merged by me, and now I think that is not perfect as well, since it also suffers from this.
   
   For `needNewSubQuery`, we should only bail out when we returns `true`. In that way, we could safely add new conditions into this method, and all the cases are orthogonal.



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