[GitHub] [calcite] danny0405 commented on a change in pull request #1606: [CALCITE-3466] Do not drop the "group by" clause of subquery in a select statement with "group by" clause in JDBC adapter.

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

danny0405 commented on a change in pull request #1606: [CALCITE-3466] Do not drop the "group by" clause of subquery in a select statement with "group by" clause in JDBC adapter.
URL: https://github.com/apache/calcite/pull/1606#discussion_r365093122
 
 

 ##########
 File path: core/src/main/java/org/apache/calcite/rel/rel2sql/SqlImplementor.java
 ##########
 @@ -1224,10 +1224,18 @@ public Builder builder(RelNode rel, Clause... clauses) {
           needNew = true;
         }
       }
-      if (rel instanceof Aggregate
-          && !dialect.supportsNestedAggregations()
-          && hasNestedAggregations((Aggregate) rel)) {
-        needNew = true;
+
+      if (rel instanceof Aggregate) {
+        Aggregate e = (Aggregate) rel;
+        final boolean nestedAgg = hasNestedAggregations(e);
+        if (withGroupBy() && (!e.getGroupSet().toList().isEmpty()
+            || !nestedAgg || !dialect.supportsNestedAggregations())) {
 
 Review comment:
   How about this code:
   ```java
       if (rel instanceof Aggregate) {
           final Aggregate agg = (Aggregate) rel;
           final boolean hasNestedAgg = hasNestedAggregations(agg);
           if (!dialect.supportsNestedAggregations()
               && hasNestedAgg) {
             needNew = true;
           } else {
             if (this.clauses.contains(Clause.GROUP_BY)) {
               // Avoids to lose the distinct attribute of inner agg.
               if (!hasNestedAgg || Aggregate.isNotGrandTotal(agg)) {
                 needNew = true;
               }
             }
           }
         }
   ```

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