Github user dongjoon-hyun commented on a diff in the pull request:
https://github.com/apache/spark/pull/16440#discussion_r94280478
--- Diff:
sql/hive-thriftserver/src/main/scala/org/apache/spark/sql/hive/thriftserver/SparkExecuteStatementOperation.scala
---
@@ -111,9 +115,15 @@ private[hive] class SparkExecuteStatementOperation(
// Reset iter to header when fetching start from first row
if (order.equals(FetchOrientation.FETCH_FIRST)) {
- val (ita, itb) = iterHeader.duplicate
- iter = ita
- iterHeader = itb
+ iter = if (useIncrementalCollect) {
+ resultList = None
+ result.toLocalIterator.asScala
+ } else {
+ if (resultList.isEmpty) {
--- End diff --
Yes. The following happens with `iterator.duplicate`.
> So, if an iterator is duplicated into A and B, and all of A is consumed,
then B will internally buffer everything from A so it can be replayed?
And, the whole result storing happens line 122 and line 245-246 for
`spark.sql.thriftServer.incrementalCollect=false` only.
```
resultList = Some(result.collect())
resultList.get.iterator
```
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