[SPARK-19727][SQL] Fix for round function that modifies original column

## What changes were proposed in this pull request?

Fix for SQL round function that modifies original column when underlying data frame is created from a local product.

    import org.apache.spark.sql.functions._

    case class NumericRow(value: BigDecimal)

    val df = spark.createDataFrame(Seq(NumericRow(BigDecimal("1.23456789"))))

    df.show()
    +--------------------+
    |               value|
    +--------------------+
    |1.234567890000000000|
    +--------------------+

    df.withColumn("value_rounded", round('value)).show()

    // before
    +--------------------+-------------+
    |               value|value_rounded|
    +--------------------+-------------+
    |1.000000000000000000|            1|
    +--------------------+-------------+

    // after
    +--------------------+-------------+
    |               value|value_rounded|
    +--------------------+-------------+
    |1.234567890000000000|            1|
    +--------------------+-------------+

## How was this patch tested?

New unit test added to existing suite `org.apache.spark.sql.MathFunctionsSuite`

Author: Wojtek Szymanski <wk.szymanski@gmail.com>

Closes #17075 from wojtek-szymanski/SPARK-19727.

1 files changed, 12 insertions, 0 deletions

diff --git a/sql/core/src/test/scala/org/apache/spark/sql/MathFunctionsSuite.scala b/sql/core/src/test/scala/org/apache/spark/sql/MathFunctionsSuite.scala
index 37443d0342..328c5395ec 100644
--- a/sql/core/src/test/scala/org/apache/spark/sql/MathFunctionsSuite.scala
+++ b/sql/core/src/test/scala/org/apache/spark/sql/MathFunctionsSuite.scala
@@ -233,6 +233,18 @@ class MathFunctionsSuite extends QueryTest with SharedSQLContext {
     )
   }
 
+  test("round/bround with data frame from a local Seq of Product") {
+    val df = spark.createDataFrame(Seq(Tuple1(BigDecimal("5.9")))).toDF("value")
+    checkAnswer(
+      df.withColumn("value_rounded", round('value)),
+      Seq(Row(BigDecimal("5.9"), BigDecimal("6")))
+    )
+    checkAnswer(
+      df.withColumn("value_brounded", bround('value)),
+      Seq(Row(BigDecimal("5.9"), BigDecimal("6")))
+    )
+  }
+
   test("exp") {
     testOneToOneMathFunction(exp, math.exp)
   }