ilooner commented on a change in pull request #1472: DRILL-6747: Fixed IOB in
HashJoin for inner and right joins on empty probe side
URL: https://github.com/apache/drill/pull/1472#discussion_r219367526
##########
File path:
exec/java-exec/src/main/java/org/apache/drill/exec/record/RecordBatch.java
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@@ -115,6 +115,14 @@
* This value will be returned only after {@link #OK_NEW_SCHEMA} has been
* returned at least once (not necessarily <em>immediately</em> after).
* </p>
+ * <p>
+ * Also after a RecordBatch returns NONE a RecordBatch should:
+ * <ul>
+ * <li>Contain the last valid schema seen by the operator.</li>
+ * <li>Contain a VectorContainer with empty columns corresponding to
the last valid schema.</li>
+ * <li>Return a record count of 0.</li>
+ * </ul>
+ * </p>
*/
NONE(false),
Review comment:
@sohami I agree that guarantee was not provided before. However, I am
proposing to change the contract in the way described in the comment. Note no
data would be associated with a record batch after it returns NONE. It would
only have a VectorContainer with **EMPTY** columns corresponding to the last
seen valid schema, and return a record count of NONE. In practice almost all
operators already do this (except they don't always zero their container).
The advantage of adding this new guarantee is that downstream operators do
not have to do book keeping when the upstream can do it for us very easily.
The details of why this was done are in the JIRA. There were many ways to
fix the issue in HashJoin but this is by far the cleanest, and less risky since
most of the code in HashJoin has no unit tests. It also has the advantage of
clarifying the behavior of RecordBatches for future operator implementations.
So I felt this approach was a win win and the best way to go about fixing the
issue. However, there should be a follow up Jira to validate the new contract I
am proposing for the rest of the operators, not just unordered reciever.
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