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[SPARK-32730][SQL] Improve LeftSemi and Existence SortMergeJoin right side buffering #29572

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[SPARK-32730][SQL] Improve LeftSemi and Existence SortMergeJoin right side buffering #29572

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1a49356
[SPARK-32730][SQL] Improve LeftSemi SortMergeJoin right side buffering
peter-toth Aug 28, 2020
acc6646
add UT
peter-toth Aug 29, 2020
037b876
drop AppendOnlyUnsafeRowArray trait
peter-toth Sep 2, 2020
3937e4c
address review comments
peter-toth Sep 3, 2020
5cf3ab3
rename param
peter-toth Sep 3, 2020
f699118
revert accidental changes
peter-toth Sep 3, 2020
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30 changes: 20 additions & 10 deletions sql/core/src/main/scala/org/apache/spark/sql/execution/joins/SortMergeJoinExec.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -156,7 +156,8 @@ case class SortMergeJoinExec(
RowIterator.fromScala(rightIter),
inMemoryThreshold,
spillThreshold,
cleanupResources
cleanupResources,
false
)

@maropu maropu Sep 3, 2020

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nit: please avoid the unnecessary changes.

@peter-toth peter-toth Sep 3, 2020

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Sorry, reverted them.

private[this] val joinRow = new JoinedRow

Expand Down Expand Up @@ -201,7 +202,8 @@ case class SortMergeJoinExec(
bufferedIter = RowIterator.fromScala(rightIter),
inMemoryThreshold,
spillThreshold,
cleanupResources
cleanupResources,
false
)
val rightNullRow = new GenericInternalRow(right.output.length)
new LeftOuterIterator(
Expand All @@ -216,7 +218,8 @@ case class SortMergeJoinExec(
bufferedIter = RowIterator.fromScala(leftIter),
inMemoryThreshold,
spillThreshold,
cleanupResources
cleanupResources,
false
)
val leftNullRow = new GenericInternalRow(left.output.length)
new RightOuterIterator(
Expand Down Expand Up @@ -251,7 +254,8 @@ case class SortMergeJoinExec(
RowIterator.fromScala(rightIter),
inMemoryThreshold,
spillThreshold,
cleanupResources
cleanupResources,
condition.isEmpty

@juliuszsompolski juliuszsompolski Sep 10, 2020

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Thanks @peter-toth !
I think this could be also added to LeftAnti join, which is also only interested in the existence of a match and doesn't need to buffer them.

@peter-toth peter-toth Sep 10, 2020

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Thanks @juliuszsompolski, I think you are right. Shall I open a follow-up PR or a different ticket?

@cloud-fan cloud-fan Sep 11, 2020

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I think a followup PR is fine.

@peter-toth peter-toth Sep 11, 2020

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I've opened #29727

)
private[this] val joinRow = new JoinedRow

Expand Down Expand Up @@ -287,7 +291,8 @@ case class SortMergeJoinExec(
RowIterator.fromScala(rightIter),
inMemoryThreshold,
spillThreshold,
cleanupResources
cleanupResources,
false
)
private[this] val joinRow = new JoinedRow

Expand Down Expand Up @@ -330,7 +335,8 @@ case class SortMergeJoinExec(
RowIterator.fromScala(rightIter),
inMemoryThreshold,
spillThreshold,
cleanupResources
cleanupResources,
condition.isEmpty
)
private[this] val joinRow = new JoinedRow

Expand Down Expand Up @@ -662,7 +668,8 @@ private[joins] class SortMergeJoinScanner(
bufferedIter: RowIterator,
inMemoryThreshold: Int,
spillThreshold: Int,
eagerCleanupResources: () => Unit) {
eagerCleanupResources: () => Unit,
bufferFirstOnly: Boolean) {

@maropu maropu Sep 3, 2020

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nit: bufferFirstOnly -> matchedBufferFirstOnly? And, please add @param, too.

@maropu maropu Sep 3, 2020

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bufferFirstOnly: Boolean = false to avoid the unnecessary changes.

@peter-toth peter-toth Sep 3, 2020

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Thanks, fixed.

private[this] var streamedRow: InternalRow = _
private[this] var streamedRowKey: InternalRow = _
private[this] var bufferedRow: InternalRow = _
Expand All @@ -673,8 +680,9 @@ private[joins] class SortMergeJoinScanner(
*/
private[this] var matchJoinKey: InternalRow = _
/** Buffered rows from the buffered side of the join. This is empty if there are no matches. */
private[this] val bufferedMatches =
new ExternalAppendOnlyUnsafeRowArray(inMemoryThreshold, spillThreshold)
private[this] val bufferedMatches: ExternalAppendOnlyUnsafeRowArray =
new ExternalAppendOnlyUnsafeRowArray(if (bufferFirstOnly) 1 else inMemoryThreshold,

@cloud-fan cloud-fan Sep 3, 2020

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how does this change avoid spilling?

@peter-toth peter-toth Sep 3, 2020

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Not this change does it, but the one in bufferMatchingRows(). This change just avoids creating a buffer larger than 1.

@maropu maropu Sep 3, 2020

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We need this change? How about just setting 1 in the caller side? https://github.com/apache/spark/pull/29572/files#diff-2649ee0724bbc5ee6a64d7de308c527eR255

@peter-toth peter-toth Sep 3, 2020

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There is another call site in existence join: https://github.com/apache/spark/pull/29572/files#diff-2649ee0724bbc5ee6a64d7de308c527eR336

spillThreshold)

// Initialization (note: do _not_ want to advance streamed here).
advancedBufferedToRowWithNullFreeJoinKey()
Expand Down Expand Up @@ -834,7 +842,9 @@ private[joins] class SortMergeJoinScanner(
matchJoinKey = streamedRowKey.copy()
bufferedMatches.clear()
do {
bufferedMatches.add(bufferedRow.asInstanceOf[UnsafeRow])
if (!bufferFirstOnly || bufferedMatches.isEmpty) {
bufferedMatches.add(bufferedRow.asInstanceOf[UnsafeRow])
}
advancedBufferedToRowWithNullFreeJoinKey()
} while (bufferedRow != null && keyOrdering.compare(streamedRowKey, bufferedRowKey) == 0)
}
Expand Down
8 changes: 8 additions & 0 deletions sql/core/src/test/scala/org/apache/spark/sql/JoinSuite.scala
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Expand Up @@ -749,6 +749,14 @@ class JoinSuite extends QueryTest with SharedSparkSession with AdaptiveSparkPlan
)
}

// LEFT SEMI JOIN without bound condition does not spill
assertNotSpilled(sparkContext, "left semi join") {

@peter-toth peter-toth Aug 29, 2020

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Without this fix this UT fails.

checkAnswer(
sql("SELECT * FROM testData LEFT SEMI JOIN testData2 ON key = a WHERE key = 2"),
Row(2, "2") :: Nil
)
}

val expected = new ListBuffer[Row]()
expected.append(
Row(1, "1", 1, 1), Row(1, "1", 1, 2),
Expand Down