[GitHub] Ben-Zvi commented on a change in pull request #1598: DRILL-6880: For Hash-Join hash-table build - treat null keys as an equal match

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Ben-Zvi commented on a change in pull request #1598: DRILL-6880: For Hash-Join hash-table build - treat null keys as an equal match 
URL: https://github.com/apache/drill/pull/1598#discussion_r245768702
 
 

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 File path: exec/java-exec/src/main/java/org/apache/drill/exec/physical/impl/common/ChainedHashTable.java
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 @@ -208,7 +216,10 @@ public HashTable createAndSetupHashTable(TypedFieldId[] outKeyFieldIds) throws C
       i++;
     }
 
-
+    // Only in case of an equi-join: Generate a special method to check if both the new key and the existing key (in this HT bucket) are nulls
 
 Review comment:
   The 'equi-join' term was just following the 'Comparator.EQUALS'; and is correct as we only support these now.
      The point here is that for *all joins*, nulls are equal on build/insert, but not equal on probe. This works the same for outer joins, as an unmatched probe on a single hash-table key is the same as un-matching multiple such keys.  Maybe I should add this to the comment to clarify. 
     

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