[GitHub] [druid] jihoonson commented on a change in pull request #9655: Fix wrong cardinality computation in BufferArrayGrouper

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

jihoonson commented on a change in pull request #9655: Fix wrong cardinality computation in BufferArrayGrouper
URL: https://github.com/apache/druid/pull/9655#discussion_r406555229
 
 

 ##########
 File path: processing/src/main/java/org/apache/druid/query/groupby/epinephelinae/BufferArrayGrouper.java
 ##########
 @@ -69,12 +69,20 @@
   @Nullable
   private int[] vAggregationRows = null;
 
-  static long requiredBufferCapacity(
-      int cardinality,
-      AggregatorFactory[] aggregatorFactories
-  )
+  /**
+   * Computes required buffer capacity for a grouping key of the given cardinaltiy and aggregatorFactories.
+   * This method assumes that the given cardinality doesn't count nulls.
+   *
+   * Returns -1 if it cardinality + 1 (for null) = Integer.MAX_VALUE. Returns computed required buffer capacity
 
 Review comment:
   Oops, thanks!

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