Consider other wrong setting values.

Author: viirya

sql/core/src/main/scala/org/apache/spark/sql/execution/commands.scala

@@ -84,8 +84,8 @@ case class SetCommand(
       logWarning(
         s"Property ${SQLConf.Deprecated.MAPRED_REDUCE_TASKS} is deprecated, " +
           s"automatically converted to ${SQLConf.SHUFFLE_PARTITIONS} instead.")
-      if (value == "-1") {
-        val msg = s"Setting ${SQLConf.Deprecated.MAPRED_REDUCE_TASKS} to -1 for automatically " +
+      if (value.toInt < 1) {
+        val msg = s"Setting negative ${SQLConf.Deprecated.MAPRED_REDUCE_TASKS} for automatically " +
           "determining the number of reducers is not supported."
         throw new IllegalArgumentException(msg)
       } else {

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

@@ -864,8 +864,11 @@ class SQLQuerySuite extends QueryTest with BeforeAndAfterAll {
 
   test("SET commands with illegal or inappropriate argument") {
     conf.clear()
-    // mapred.reduce.tasks=-1 for automatically determing the number of reducers is not supported
+    // Set negative mapred.reduce.tasks for automatically determing
+    // the number of reducers is not supported
     intercept[IllegalArgumentException](sql(s"SET mapred.reduce.tasks=-1"))
+    intercept[IllegalArgumentException](sql(s"SET mapred.reduce.tasks=-01"))
+    intercept[IllegalArgumentException](sql(s"SET mapred.reduce.tasks=-2"))
     conf.clear()
   }