Github user Dooyoung-Hwang commented on a diff in the pull request:
https://github.com/apache/spark/pull/22347#discussion_r222623133
--- Diff:
sql/core/src/main/scala/org/apache/spark/sql/execution/SparkPlan.scala ---
@@ -348,30 +349,30 @@ abstract class SparkPlan extends QueryPlan[SparkPlan]
with Logging with Serializ
// Otherwise, interpolate the number of partitions we need to try,
but overestimate
// it by 50%. We also cap the estimation in the end.
val limitScaleUpFactor =
Math.max(sqlContext.conf.limitScaleUpFactor, 2)
- if (buf.isEmpty) {
+ if (scannedRowCount == 0) {
numPartsToTry = partsScanned * limitScaleUpFactor
} else {
- val left = n - buf.size
+ val left = n - scannedRowCount
// As left > 0, numPartsToTry is always >= 1
- numPartsToTry = Math.ceil(1.5 * left * partsScanned /
buf.size).toInt
+ numPartsToTry = Math.ceil(1.5 * left * partsScanned /
scannedRowCount).toInt
numPartsToTry = Math.min(numPartsToTry, partsScanned *
limitScaleUpFactor)
}
}
val p = partsScanned.until(math.min(partsScanned + numPartsToTry,
totalParts).toInt)
val sc = sqlContext.sparkContext
- val res = sc.runJob(childRDD,
- (it: Iterator[Array[Byte]]) => if (it.hasNext) it.next() else
Array.empty[Byte], p)
-
- buf ++= res.flatMap(decodeUnsafeRows)
+ val res = sc.runJob(childRDD, (it: Iterator[(Long, Array[Byte])]) =>
+ if (it.hasNext) it.next() else (0L, Array.empty[Byte]), p)
+ buf ++= res.map(_._2)
+ scannedRowCount += res.map(_._1).sum
partsScanned += p.size
}
- if (buf.size > n) {
- buf.take(n).toArray
+ if (scannedRowCount > n) {
+ buf.toArray.view.flatMap(decodeUnsafeRows).take(n).force
--- End diff --
If the part of calling "view" is removed, no behavior changes compared to
before. If you don't want to use view here, what about "iterator" instead of
"view".
It would be like this.
buf.iterator.flatMap(decodeUnsafeRows).take(n).toArray
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