Revert "[SPARK-8800] [SQL] Fix inaccurate precision/scale of Decimal division operation"

This reverts commit 4b5cfc9.

Author: yhuai

sql/catalyst/src/main/scala/org/apache/spark/sql/types/Decimal.scala

@@ -145,14 +145,6 @@ final class Decimal extends Ordered[Decimal] with Serializable {
     }
   }
 
-  def toLimitedBigDecimal: BigDecimal = {
-    if (decimalVal.ne(null)) {
-      decimalVal
-    } else {
-      BigDecimal(longVal, _scale)
-    }
-  }
-
   def toJavaBigDecimal: java.math.BigDecimal = toBigDecimal.underlying()
 
   def toUnscaledLong: Long = {
@@ -277,9 +269,9 @@ final class Decimal extends Ordered[Decimal] with Serializable {
     if (that.isZero) {
       null
     } else {
-      // To avoid non-terminating decimal expansion problem, we get scala's BigDecimal with limited
-      // precision and scala.
-      Decimal(toLimitedBigDecimal / that.toLimitedBigDecimal)
+      // To avoid non-terminating decimal expansion problem, we turn to Java BigDecimal's divide
+      // with specified ROUNDING_MODE.
+      Decimal(toJavaBigDecimal.divide(that.toJavaBigDecimal, ROUNDING_MODE.id))
     }
   }
 

sql/catalyst/src/test/scala/org/apache/spark/sql/types/decimal/DecimalSuite.scala

@@ -179,14 +179,6 @@ class DecimalSuite extends SparkFunSuite with PrivateMethodTester {
 
   test("fix non-terminating decimal expansion problem") {
     val decimal = Decimal(1.0, 10, 3) / Decimal(3.0, 10, 3)
-    // The difference between decimal should not be more than 0.001.
-    assert(decimal.toDouble - 0.333 < 0.001)
-  }
-
-  test("fix loss of precision/scale when doing division operation") {
-    val a = Decimal(2) / Decimal(3)
-    assert(a.toDouble < 1.0 && a.toDouble > 0.6)
-    val b = Decimal(1) / Decimal(8)
-    assert(b.toDouble === 0.125)
+    assert(decimal.toString === "0.333")
   }
 }