[GitHub] [calcite] dssysolyatin commented on a diff in pull request #2977: [CALCITE-5388] No result when using ROW_NUMBER in two common table expressions

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

dssysolyatin commented on code in PR #2977:
URL: https://github.com/apache/calcite/pull/2977#discussion_r1038206955


##########
core/src/main/java/org/apache/calcite/adapter/enumerable/EnumerableWindow.java:
##########
@@ -693,7 +696,7 @@ private static Pair<Expression, Expression> getPartitionIterator(
     }
     Expression multiMap_ =
         builder.append(
-            "multiMap", Expressions.new_(SortedMultiMap.class));
+            "multiMap", Expressions.new_(SortedMultiMap.class), false);

Review Comment:
   @libenchao @rubenada As I wrote above "multiMap" case works without this fix. 
   But it works only because expressions which create and fill multiMap are different. 
   I set optimize flag = true for "multiMap" only for safety, because it is really easy to make a mistake here. 
   I am not against optimizations, but in my opinion, this optimization does more harm than good. 
   
   ```
   Pseudo code for "multiMap" case
   <-- first EnumerableWindow -->
   multiMap = new SortedMultiMap() <-- luckely optimizer caches only this expression
   fillMultimap(multiMap)
   multiMap.clear()
   
   <-- second EnumerableWindow -->
   fillMap(multiMap)
   multiMap.clear()
   ```



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