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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