[GitHub] [incubator-pinot] Jackie-Jiang commented on a change in pull request #5419: [WIP]Use thread local for groupby raw key holders

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

Jackie-Jiang commented on a change in pull request #5419:
URL: https://github.com/apache/incubator-pinot/pull/5419#discussion_r428187692



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File path: pinot-core/src/main/java/org/apache/pinot/core/query/aggregation/groupby/DictionaryBasedGroupKeyGenerator.java
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@@ -106,18 +108,26 @@ public DictionaryBasedGroupKeyGenerator(TransformOperator transformOperator,
 
       _isSingleValueColumn[i] = transformOperator.getResultMetadata(groupByExpression).isSingleValue();
     }
-
     if (longOverflow) {
       _globalGroupIdUpperBound = numGroupsLimit;
-      _rawKeyHolder = new ArrayMapBasedHolder(_globalGroupIdUpperBound);
+      if (!mapBasedRawKeyHolders.containsKey(ArrayMapBasedHolder.class.getName())) {

Review comment:
       Use `computeIfAbsent()` to save one extra map lookup.
   Also, because you already know the type of key holders, maybe add a separate class to store different type of holders without map lookup?




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