Github user dongjoon-hyun commented on a diff in the pull request: https://github.com/apache/spark/pull/16440#discussion_r94495291 --- 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 -- `collect()` is still intended to be called once logically. The following is the reason why there exists two `collect()`. When `useIncrementalCollect=false`, `collect()` is called at [line 244](https://github.com/apache/spark/pull/16440/files#diff-72dcd8f81a51c8a815159fdf0332acdcR244) **once** and `resultList` will not be `None`. However, if users executes a query with `useIncrementalCollect=true` and they changes their mind to turn off as `useIncrementalCollect=false`. The next `getNextRowSet(FetchOrientation.FETCH_FIRST)` should check `resultList` and fill that by calling `collect()` **once** in [line 123](https://github.com/apache/spark/pull/16440/files#diff-72dcd8f81a51c8a815159fdf0332acdcR123).
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