[SPARK-14914][CORE][SQL] Skip/fix some test cases on Windows due to limitation of Windows

core/src/main/scala/org/apache/spark/util/Utils.scala

@@ -23,7 +23,7 @@ import java.net._
 import java.nio.ByteBuffer
 import java.nio.channels.Channels
 import java.nio.charset.StandardCharsets
-import java.nio.file.Files
+import java.nio.file.{Files, Paths}
 import java.util.{Locale, Properties, Random, UUID}
 import java.util.concurrent._
 import java.util.concurrent.atomic.AtomicBoolean
@@ -1014,15 +1014,7 @@ private[spark] object Utils extends Logging {
    * Check to see if file is a symbolic link.
    */
   def isSymlink(file: File): Boolean = {
-    if (file == null) throw new NullPointerException("File must not be null")
-    if (isWindows) return false
-    val fileInCanonicalDir = if (file.getParent() == null) {
-      file
-    } else {
-      new File(file.getParentFile().getCanonicalFile(), file.getName())
-    }
-
-    !fileInCanonicalDir.getCanonicalFile().equals(fileInCanonicalDir.getAbsoluteFile())
+    return Files.isSymbolicLink(Paths.get(file.toURI))
   }
 
   /**

core/src/test/scala/org/apache/spark/deploy/SparkSubmitSuite.scala

@@ -649,8 +649,13 @@ class SparkSubmitSuite
   // NOTE: This is an expensive operation in terms of time (10 seconds+). Use sparingly.
   private def runSparkSubmit(args: Seq[String]): Unit = {
     val sparkHome = sys.props.getOrElse("spark.test.home", fail("spark.test.home is not set!"))
+    val sparkSubmitFile = if (Utils.isWindows) {
+      new File("..\\bin\\spark-submit.cmd")
+    } else {
+      new File("../bin/spark-submit")
+    }
     val process = Utils.executeCommand(
-      Seq("./bin/spark-submit") ++ args,
+      Seq(sparkSubmitFile.getCanonicalPath) ++ args,
       new File(sparkHome),
       Map("SPARK_TESTING" -> "1", "SPARK_HOME" -> sparkHome))
 

core/src/test/scala/org/apache/spark/deploy/history/FsHistoryProviderSuite.scala

@@ -126,6 +126,8 @@ class FsHistoryProviderSuite extends SparkFunSuite with BeforeAndAfter with Matc
   }
 
   test("SPARK-3697: ignore directories that cannot be read.") {
+    // setReadable(...) does not work on Windows. Please refer JDK-6728842.
+    assume(!Utils.isWindows)
     val logFile1 = newLogFile("new1", None, inProgress = false)
     writeFile(logFile1, true, None,
       SparkListenerApplicationStart("app1-1", Some("app1-1"), 1L, "test", None),

core/src/test/scala/org/apache/spark/storage/DiskStoreSuite.scala

@@ -22,10 +22,14 @@ import java.util.Arrays
 
 import org.apache.spark.{SparkConf, SparkFunSuite}
 import org.apache.spark.util.io.ChunkedByteBuffer
+import org.apache.spark.util.Utils
 
 class DiskStoreSuite extends SparkFunSuite {
 
   test("reads of memory-mapped and non memory-mapped files are equivalent") {
+    // It will cause error when we tried to re-open the filestore and the
+    // memory-mapped byte buffer tot he file has not been GC on Windows.
+    assume(!Utils.isWindows)
     val confKey = "spark.storage.memoryMapThreshold"
 
     // Create a non-trivial (not all zeros) byte array

sql/core/src/test/scala/org/apache/spark/sql/sources/CreateTableAsSelectSuite.scala

@@ -26,7 +26,6 @@ import org.apache.spark.sql.AnalysisException
 import org.apache.spark.sql.catalyst.TableIdentifier
 import org.apache.spark.sql.catalyst.catalog.BucketSpec
 import org.apache.spark.sql.catalyst.parser.ParseException
-import org.apache.spark.sql.execution.command.DDLUtils
 import org.apache.spark.sql.test.SharedSQLContext
 import org.apache.spark.util.Utils
 
@@ -83,6 +82,8 @@ class CreateTableAsSelectSuite
   }
 
   test("CREATE TABLE USING AS SELECT based on the file without write permission") {
+    // setWritable(...) does not work on Windows. Please refer JDK-6728842.
+    assume(!Utils.isWindows)
     val childPath = new File(path.toString, "child")
     path.mkdir()
     path.setWritable(false)