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[SPARK-22176][SQL] Fix overflow issue in Dataset.show #19401

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[SPARK-22176][SQL] Fix overflow issue in Dataset.show #19401

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f988766
Fix overflow issue in Dataset.show
maropu Sep 30, 2017
340243c
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maropu Sep 30, 2017
bbf2c39
Fix more
maropu Sep 30, 2017
99c988a
Fix
maropu Oct 1, 2017
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2 changes: 1 addition & 1 deletion sql/core/src/main/scala/org/apache/spark/sql/Dataset.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -237,7 +237,7 @@ class Dataset[T] private[sql](
*/
private[sql] def showString(
_numRows: Int, truncate: Int = 20, vertical: Boolean = false): String = {
val numRows = _numRows.max(0)
val numRows = _numRows.max(0).min(Int.MaxValue - 1)
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@srowen srowen Oct 1, 2017

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OK, but now you return one fewer row than expected when it's possible to return Int.MaxValue. Granted this is an extreme corner case, but that seems less compelling than just skipping the display of "more elements" in this case.

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@maropu maropu Oct 1, 2017 •
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hmm, I see. Both is okay to me and WDYT? cc: @gatorsmile
IMHO it might be still okay to set [0, Int.MaxValue) as valid range for show cuz this is a corner case.

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@gatorsmile gatorsmile Oct 1, 2017 •
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DataFrame.show() does not work when the number of rows is close to Int.MaxValue. The driver will be OOM before finishing the command. Thus, I do not think we can hit this extreme case.

val takeResult = toDF().take(numRows + 1)
val hasMoreData = takeResult.length > numRows
val data = takeResult.take(numRows)
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12 changes: 12 additions & 0 deletions sql/core/src/test/scala/org/apache/spark/sql/DataFrameSuite.scala
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Expand Up @@ -993,6 +993,18 @@ class DataFrameSuite extends QueryTest with SharedSQLContext {
assert(testData.select($"*").showString(0) === expectedAnswer)
}

test("showString(Int.MaxValue)") {
val df = Seq((1, 2), (3, 4)).toDF("a", "b")
val expectedAnswer = """+---+---+
|| a| b|
|+---+---+
|| 1| 2|
|| 3| 4|
|+---+---+
|""".stripMargin
assert(df.showString(Int.MaxValue) === expectedAnswer)
}

test("showString(0), vertical = true") {
val expectedAnswer = "(0 rows)\n"
assert(testData.select($"*").showString(0, vertical = true) === expectedAnswer)
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