JoshRosen commented on a change in pull request #27246:
[SPARK-30536][CORE][SQL] Sort-merge join operator spilling performance
improvements
URL: https://github.com/apache/spark/pull/27246#discussion_r369918361
##########
File path:
sql/core/src/main/scala/org/apache/spark/sql/execution/ExternalAppendOnlyUnsafeRowArray.scala
##########
@@ -204,22 +195,44 @@ private[sql] class ExternalAppendOnlyUnsafeRowArray(
}
}
- private[this] class SpillableArrayIterator(
+ private[this] class MergerIterator(
iterator: UnsafeSorterIterator,
- numFieldPerRow: Int)
+ numFieldPerRow: Int,
+ startIndex: Int)
extends ExternalAppendOnlyUnsafeRowArrayIterator {
- private val currentRow = new UnsafeRow(numFieldPerRow)
+ private var currentIndex = startIndex
- override def hasNext(): Boolean = !isModified() && iterator.hasNext
+ private val currentRow = {
+ if (startIndex < numRows) {
+ inMemoryBuffer(currentIndex)
+ } else {
+ new UnsafeRow(numFieldPerRow)
+ }
+ }
+
+ override def hasNext(): Boolean = {
+ if (currentIndex < numRows) {
+ !isModified()
+ } else {
+ !isModified() && iterator.hasNext
+ }
+ }
override def next(): UnsafeRow = {
throwExceptionIfModified()
- iterator.loadNext()
- currentRow.pointTo(iterator.getBaseObject, iterator.getBaseOffset,
iterator.getRecordLength)
- currentRow
+ if (currentIndex < numRows) {
+ val result = inMemoryBuffer(currentIndex)
+ currentIndex += 1
+ result
+ } else {
+ iterator.loadNext()
+ currentRow.pointTo(iterator.getBaseObject, iterator.getBaseOffset,
iterator.getRecordLength)
Review comment:
If `startIndex < numRows` then `currentRow` will be an `UnsafeRow` in
`inMemoryBuffer`, so when we then roll past the `numRows` boundary then we'd
start mutating that `UnsafeRow`'s state (which would corrupt the data in case
we iterated over this multiple times).
As a result, I think it's safer to leave `currentRow` as it was defined
before, but rename it to, say, `currentSorterRow` to make it clear that it's
only used for pointing at spilled records.
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