[GitHub] [hive] jcamachor commented on a change in pull request #557: HIVE-21338 Remove order by and limit for aggregates

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jcamachor commented on a change in pull request #557: HIVE-21338 Remove order by and limit for aggregates
URL: https://github.com/apache/hive/pull/557#discussion_r262705631
 
 

 ##########
 File path: ql/src/java/org/apache/hadoop/hive/ql/optimizer/calcite/HiveRelOptUtil.java
 ##########
 @@ -1047,4 +1052,37 @@ public static String toJsonString(final RelNode rel) {
     return planWriter.asString();
   }
 
+
+  /**
+   * Utility method to answer if given a rel plan it will produce at most
+   *  one row.
+   */
+  public static boolean produceAtmostOneRow(RelNode rel) {
+    if(rel instanceof HepRelVertex) {
+      rel = ((HepRelVertex)rel).getCurrentRel();
+    }
+    if(rel instanceof HiveProject) {
+      if(((HiveProject)rel).hasWindowingExpr()) {
 
 Review comment:
   This check does not seem to be needed since the window expression will not alter the number of rows output by the Project.

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