[SPARK-26233][SQL][BACKPORT-2.4] CheckOverflow when encoding a decimal value

## What changes were proposed in this pull request?

When we encode a Decimal from external source we don't check for overflow. That method is useful not only in order to enforce that we can represent the correct value in the specified range, but it also changes the underlying data to the right precision/scale. Since in our code generation we assume that a decimal has exactly the same precision and scale of its data type, missing to enforce it can lead to corrupted output/results when there are subsequent transformations.

## How was this patch tested?

added UT

Closes apache#23232 from mgaido91/SPARK-26233_2.4.

Authored-by: Marco Gaido <marcogaido91@gmail.com>
Signed-off-by: Dongjoon Hyun <dongjoon@apache.org>

Author: mgaido91

sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/encoders/RowEncoder.scala

@@ -108,12 +108,12 @@ object RowEncoder {
         returnNullable = false)
 
     case d: DecimalType =>
-      StaticInvoke(
+      CheckOverflow(StaticInvoke(
         Decimal.getClass,
         d,
         "fromDecimal",
         inputObject :: Nil,
-        returnNullable = false)
+        returnNullable = false), d)
 
     case StringType =>
       StaticInvoke(

sql/core/src/test/scala/org/apache/spark/sql/DatasetSuite.scala

@@ -1547,6 +1547,15 @@ class DatasetSuite extends QueryTest with SharedSQLContext {
       df.where($"city".contains(new java.lang.Character('A'))),
       Seq(Row("Amsterdam")))
   }
+
+  test("SPARK-26233: serializer should enforce decimal precision and scale") {
+    val s = StructType(Seq(StructField("a", StringType), StructField("b", DecimalType(38, 8))))
+    val encoder = RowEncoder(s)
+    implicit val uEnc = encoder
+    val df = spark.range(2).map(l => Row(l.toString, BigDecimal.valueOf(l + 0.1111)))
+    checkAnswer(df.groupBy(col("a")).agg(first(col("b"))),
+      Seq(Row("0", BigDecimal.valueOf(0.1111)), Row("1", BigDecimal.valueOf(1.1111))))
+  }
 }
 
 case class TestDataUnion(x: Int, y: Int, z: Int)