vanzin commented on a change in pull request #26108: [SPARK-26154][SS]
Streaming left/right outer join should not return outer nulls for already
matched rows
URL: https://github.com/apache/spark/pull/26108#discussion_r338822804
##########
File path:
sql/core/src/main/scala/org/apache/spark/sql/execution/streaming/StreamingSymmetricHashJoinExec.scala
##########
@@ -270,20 +279,30 @@ case class StreamingSymmetricHashJoinExec(
// * Getting an iterator over the rows that have aged out on the left
side. These rows are
// candidates for being null joined. Note that to avoid doing two
passes, this iterator
// removes the rows from the state manager as they're processed.
- // * Checking whether the current row matches a key in the right side
state, and that key
- // has any value which satisfies the filter function when joined. If
it doesn't,
- // we know we can join with null, since there was never (including
this batch) a match
- // within the watermark period. If it does, there must have been a
match at some point, so
- // we know we can't join with null.
+ // * (state format version 1) Checking whether the current row matches
a key in the
+ // right side state, and that key has any value which satisfies the
filter function when
+ // joined. If it doesn't, we know we can join with null, since there
was never
+ // (including this batch) a match within the watermark period. If it
does, there must have
+ // been a match at some point, so we know we can't join with null.
+ // * (state format version 2) We found edge-case of above approach
which brings correctness
+ // issue, and had to take another approach (see SPARK-26154); now
Spark stores 'matched'
+ // flag along with row, which is set to true when there's any
matching row on the right.
+
def matchesWithRightSideState(leftKeyValue: UnsafeRowPair) = {
rightSideJoiner.get(leftKeyValue.key).exists { rightValue =>
postJoinFilter(joinedRow.withLeft(leftKeyValue.value).withRight(rightValue))
}
}
val removedRowIter = leftSideJoiner.removeOldState()
- val outerOutputIter = removedRowIter
- .filterNot(pair => matchesWithRightSideState(pair))
- .map(pair => joinedRow.withLeft(pair.value).withRight(nullRight))
+ val outerOutputIter = removedRowIter.filterNot { kvAndMatched =>
+ stateFormatVersion match {
+ case 1 => matchesWithRightSideState(
+ new UnsafeRowPair(kvAndMatched.key, kvAndMatched.value))
+ case 2 => kvAndMatched.matched
+ case _ => throw new IllegalStateException("Incorrect state format
version! " +
Review comment:
s/Incorrect/Invalid (or Unexpected).
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