[SPARK-37451][SQL] Fix cast string type to decimal type if spark.sql.…

…legacy.allowNegativeScaleOfDecimal is enabled

### What changes were proposed in this pull request?

Fix cast string type to decimal type only if `spark.sql.legacy.allowNegativeScaleOfDecimal` is enabled. For example:
```scala
import org.apache.spark.sql.types._
import org.apache.spark.sql.Row

spark.conf.set("spark.sql.legacy.allowNegativeScaleOfDecimal", true)
val data = Seq(Row("7.836725755512218E38"))
val schema = StructType(Array(StructField("a", StringType, false)))
val df =spark.createDataFrame(spark.sparkContext.parallelize(data), schema)
df.select(col("a").cast(DecimalType(37,-17))).show
```

The result is null since [SPARK-32706](https://issues.apache.org/jira/browse/SPARK-32706).

### Why are the changes needed?

Fix regression bug.

### Does this PR introduce _any_ user-facing change?

No.

### How was this patch tested?

Unit test.

Closes apache#34811 from wangyum/SPARK-37451.

Authored-by: Yuming Wang <yumwang@ebay.com>
Signed-off-by: Dongjoon Hyun <dongjoon@apache.org>

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

@@ -602,7 +602,8 @@ object Decimal {
       val bigDecimal = stringToJavaBigDecimal(str)
       // We fast fail because constructing a very large JavaBigDecimal to Decimal is very slow.
       // For example: Decimal("6.0790316E+25569151")
-      if (numDigitsInIntegralPart(bigDecimal) > DecimalType.MAX_PRECISION) {
+      if (numDigitsInIntegralPart(bigDecimal) > DecimalType.MAX_PRECISION &&
+          !SQLConf.get.allowNegativeScaleOfDecimalEnabled) {
         null
       } else {
         Decimal(bigDecimal)
@@ -618,7 +619,8 @@ object Decimal {
       val bigDecimal = stringToJavaBigDecimal(str)
       // We fast fail because constructing a very large JavaBigDecimal to Decimal is very slow.
       // For example: Decimal("6.0790316E+25569151")
-      if (numDigitsInIntegralPart(bigDecimal) > DecimalType.MAX_PRECISION) {
+      if (numDigitsInIntegralPart(bigDecimal) > DecimalType.MAX_PRECISION &&
+          !SQLConf.get.allowNegativeScaleOfDecimalEnabled) {
         throw QueryExecutionErrors.outOfDecimalTypeRangeError(str)
       } else {
         Decimal(bigDecimal)

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

@@ -299,4 +299,19 @@ class DecimalSuite extends SparkFunSuite with PrivateMethodTester with SQLHelper
       assert(Decimal.fromStringANSI(UTF8String.fromString(string)) === Decimal(string))
     }
   }
+
+  test("SPARK-37451: Performance improvement regressed String to Decimal cast") {
+    val values = Array("7.836725755512218E38")
+    for (string <- values) {
+      assert(Decimal.fromString(UTF8String.fromString(string)) === null)
+      intercept[ArithmeticException](Decimal.fromStringANSI(UTF8String.fromString(string)))
+    }
+
+    withSQLConf(SQLConf.LEGACY_ALLOW_NEGATIVE_SCALE_OF_DECIMAL_ENABLED.key -> "true") {
+      for (string <- values) {
+        assert(Decimal.fromString(UTF8String.fromString(string)) === Decimal(string))
+        assert(Decimal.fromStringANSI(UTF8String.fromString(string)) === Decimal(string))
+      }
+    }
+  }
 }