Skip the fast-fail for zero

Zero fits any decimal type whatever its exponent, so strings like '0e39' should not be
rejected as out of range.

Co-authored-by: Isaac <no-reply@databricks.com>

Author: viirya

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

@@ -649,8 +649,10 @@ object Decimal {
     try {
       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 &&
+      // For example: Decimal("6.0790316E+25569151"). Zero fits any decimal type whatever its
+      // exponent, e.g. "0e39", so it is not checked.
+      if (bigDecimal.signum != 0 &&
+        numDigitsInIntegralPart(bigDecimal) > DecimalType.MAX_PRECISION &&
         !SqlApiConf.get.allowNegativeScaleOfDecimalEnabled) {
         null
       } else {
@@ -669,8 +671,10 @@ object Decimal {
     try {
       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 &&
+      // For example: Decimal("6.0790316E+25569151"). Zero fits any decimal type whatever its
+      // exponent, e.g. "0e39", so it is not checked.
+      if (bigDecimal.signum != 0 &&
+        numDigitsInIntegralPart(bigDecimal) > DecimalType.MAX_PRECISION &&
         !SqlApiConf.get.allowNegativeScaleOfDecimalEnabled) {
         throw DataTypeErrors.outOfDecimalTypeRangeError(str)
       } else {

sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/expressions/CastWithAnsiOffSuite.scala

@@ -559,9 +559,12 @@ class CastWithAnsiOffSuite extends CastSuiteBase {
       Decimal("60000000000000000000000000000000000000"))
     checkEvaluation(cast("6E+38", DecimalType(38, 0)), null)
     checkEvaluation(cast("6E+37", DecimalType(38, 1)), null)
-    Seq("1e2147483647", "0e2147483647", "1.5e2147483647", "1e2147483648").foreach { s =>
+    Seq("1e2147483647", "1.5e2147483647", "1e2147483648").foreach { s =>
       checkEvaluation(cast(s, DecimalType(10, 2)), null)
     }
+    Seq("0e39", "0e2147483647", "0.0e2147483648").foreach { s =>
+      checkEvaluation(cast(s, DecimalType(10, 2)), Decimal("0.00"))
+    }
 
     checkEvaluation(cast("abcd", DecimalType(38, 1)), null)
   }

sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/expressions/CastWithAnsiOnSuite.scala

@@ -475,11 +475,14 @@ class CastWithAnsiOnSuite extends CastSuiteBase with QueryErrorsBase {
     checkExceptionInExpression[ArithmeticException](
       cast("6E+37", DecimalType(38, 1)),
       "cannot be represented as Decimal(38, 1)")
-    Seq("1e2147483647", "0e2147483647", "1.5e2147483647", "1e2147483648").foreach { s =>
+    Seq("1e2147483647", "1.5e2147483647", "1e2147483648").foreach { s =>
       checkExceptionInExpression[ArithmeticException](
         cast(s, DecimalType(10, 2)),
         "NUMERIC_OUT_OF_SUPPORTED_RANGE")
     }
+    Seq("0e39", "0e2147483647", "0.0e2147483648").foreach { s =>
+      checkEvaluation(cast(s, DecimalType(10, 2)), Decimal("0.00"))
+    }
 
     checkExceptionInExpression[NumberFormatException](
       cast("abcd", DecimalType(38, 1)),

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

@@ -448,15 +448,20 @@ class DecimalSuite extends SparkFunSuite with PrivateMethodTester with SQLHelper
 
   test("UTF8String to Decimal with exponent near Int.MaxValue") {
     // The number of integral digits (precision - scale) of these values overflows Int.
-    Seq("1e2147483647", "-1E+2147483647", "0e2147483647", "12e2147483647",
-      "1.5e2147483647", "1e2147483648").foreach { string =>
+    Seq("1e2147483647", "-1E+2147483647", "12e2147483647", "1.5e2147483647",
+      "1e2147483648").foreach { string =>
       assert(Decimal.fromString(UTF8String.fromString(string)) === null)
       checkError(
         exception = intercept[SparkArithmeticException](
           Decimal.fromStringANSI(UTF8String.fromString(string))),
         condition = "NUMERIC_OUT_OF_SUPPORTED_RANGE",
         parameters = Map("value" -> string))
     }
+    // Zero fits any decimal type whatever its exponent.
+    Seq("0e39", "-0E+100", "0e2147483647", "0.0e2147483648").foreach { string =>
+      assert(Decimal.fromString(UTF8String.fromString(string)) === Decimal(0))
+      assert(Decimal.fromStringANSI(UTF8String.fromString(string)) === Decimal(0))
+    }
   }
 
   // 18 is a max number of digits in Decimal's compact long