Fixes doc typos. Fixes partition discovery refresh.

sql/core/src/main/scala/org/apache/spark/sql/sources/ddl.scala

@@ -224,10 +224,16 @@ private[sql] object ResolvedDataSource {
         case dataSource: SchemaRelationProvider =>
           dataSource.createRelation(sqlContext, new CaseInsensitiveMap(options), schema)
         case dataSource: FSBasedRelationProvider =>
+          val maybePartitionsSchema = if (partitionColumns.isEmpty) {
+            None
+          } else {
+            Some(partitionColumnsSchema(schema, partitionColumns))
+          }
+
           dataSource.createRelation(
             sqlContext,
             Some(schema),
-            Some(partitionColumnsSchema(schema, partitionColumns)),
+            maybePartitionsSchema,
             new CaseInsensitiveMap(options))
         case dataSource: org.apache.spark.sql.sources.RelationProvider =>
           throw new AnalysisException(s"$className does not allow user-specified schemas.")

sql/core/src/main/scala/org/apache/spark/sql/sources/interfaces.scala

@@ -20,7 +20,6 @@ package org.apache.spark.sql.sources
 import org.apache.hadoop.conf.Configuration
 import org.apache.hadoop.fs.{FileStatus, Path}
 import org.apache.hadoop.mapreduce.{Job, TaskAttemptContext}
-import org.apache.hadoop.mapreduce.lib.output.FileOutputCommitter
 
 import org.apache.spark.annotation.{DeveloperApi, Experimental}
 import org.apache.spark.deploy.SparkHadoopUtil
@@ -294,7 +293,7 @@ abstract class OutputWriter {
  * filter using selected predicates before producing an RDD containing all matching tuples as
  * [[Row]] objects. In addition, when reading from Hive style partitioned tables stored in file
  * systems, it's able to discover partitioning information from the paths of input directories, and
- * perform partition pruning before start reading the data.Subclasses of [[FSBasedRelation()]] must
+ * perform partition pruning before start reading the data. Subclasses of [[FSBasedRelation()]] must
  * override one of the three `buildScan` methods to implement the read path.
  *
  * For the write path, it provides the ability to write to both non-partitioned and partitioned
@@ -329,39 +328,45 @@ abstract class FSBasedRelation private[sql](
   /**
    * Constructs an [[FSBasedRelation]].
    *
-   * @param paths Base paths of this relation.  For partitioned relations, it should be either root
+   * @param paths Base paths of this relation.  For partitioned relations, it should be root
    *        directories of all partition directories.
    */
   def this(paths: Array[String]) = this(paths, None)
 
   private val hadoopConf = new Configuration(sqlContext.sparkContext.hadoopConfiguration)
 
-  private var _partitionSpec: PartitionSpec = _
-  refreshPartitions()
+  private var _partitionSpec: PartitionSpec = maybePartitionSpec.map { spec =>
+    spec.copy(partitionColumns = spec.partitionColumns.asNullable)
+  }.getOrElse {
+    discoverPartitions()
+  }
 
   private[sql] def partitionSpec: PartitionSpec = _partitionSpec
 
+  /**
+   * Partition columns. Note that they are always nullable.
+   */
+  def partitionColumns: StructType = partitionSpec.partitionColumns
+
   private[sql] def refresh(): Unit = {
-    refreshPartitions()
+    _partitionSpec = discoverPartitions()
   }
 
-  private def refreshPartitions(): Unit = {
-    _partitionSpec = maybePartitionSpec.getOrElse {
-      val basePaths = paths.map(new Path(_))
-      val leafDirs = basePaths.flatMap { path =>
-        val fs = path.getFileSystem(hadoopConf)
-        if (fs.exists(path)) {
-          SparkHadoopUtil.get.listLeafDirStatuses(fs, fs.makeQualified(path))
-        } else {
-          Seq.empty[FileStatus]
-        }
-      }.map(_.getPath)
-
-      if (leafDirs.nonEmpty) {
-        PartitioningUtils.parsePartitions(leafDirs, "__HIVE_DEFAULT_PARTITION__")
+  private def discoverPartitions(): PartitionSpec = {
+    val basePaths = paths.map(new Path(_))
+    val leafDirs = basePaths.flatMap { path =>
+      val fs = path.getFileSystem(hadoopConf)
+      if (fs.exists(path)) {
+        SparkHadoopUtil.get.listLeafDirStatuses(fs, fs.makeQualified(path))
       } else {
-        PartitionSpec(StructType(Array.empty[StructField]), Array.empty[Partition])
+        Seq.empty[FileStatus]
       }
+    }.map(_.getPath)
+
+    if (leafDirs.nonEmpty) {
+      PartitioningUtils.parsePartitions(leafDirs, "__HIVE_DEFAULT_PARTITION__")
+    } else {
+      PartitionSpec(StructType(Array.empty[StructField]), Array.empty[Partition])
     }
   }
 

sql/hive/src/test/scala/org/apache/spark/sql/sources/FSBasedRelationSuite.scala

@@ -269,34 +269,6 @@ class FSBasedRelationSuite extends QueryTest with ParquetTest {
     }
   }
 
-  ignore("save()/load() - partitioned table - Append - mismatched partition columns") {
-    withTempPath { file =>
-      partitionedTestDF1.save(
-        source = classOf[SimpleTextSource].getCanonicalName,
-        mode = SaveMode.Overwrite,
-        options = Map("path" -> file.getCanonicalPath),
-        partitionColumns = Seq("p1", "p2"))
-
-      // Using only a subset of all partition columns
-      intercept[IllegalArgumentException] {
-        partitionedTestDF2.save(
-          source = classOf[SimpleTextSource].getCanonicalName,
-          mode = SaveMode.Append,
-          options = Map("path" -> file.getCanonicalPath),
-          partitionColumns = Seq("p1"))
-      }
-
-      // Using different order of partition columns
-      intercept[IllegalArgumentException] {
-        partitionedTestDF2.save(
-          source = classOf[SimpleTextSource].getCanonicalName,
-          mode = SaveMode.Append,
-          options = Map("path" -> file.getCanonicalPath),
-          partitionColumns = Seq("p2", "p1"))
-      }
-    }
-  }
-
   test("save()/load() - partitioned table - ErrorIfExists") {
     withTempDir { file =>
       intercept[RuntimeException] {
@@ -452,7 +424,7 @@ class FSBasedRelationSuite extends QueryTest with ParquetTest {
     }
   }
 
-  ignore("saveAsTable()/load() - partitioned table - Append - mismatched partition columns") {
+  test("saveAsTable()/load() - partitioned table - Append - mismatched partition columns") {
     partitionedTestDF1.saveAsTable(
       tableName = "t",
       source = classOf[SimpleTextSource].getCanonicalName,
@@ -461,21 +433,21 @@ class FSBasedRelationSuite extends QueryTest with ParquetTest {
       partitionColumns = Seq("p1", "p2"))
 
     // Using only a subset of all partition columns
-    intercept[IllegalArgumentException] {
+    intercept[Throwable] {
       partitionedTestDF2.saveAsTable(
         tableName = "t",
         source = classOf[SimpleTextSource].getCanonicalName,
-        mode = SaveMode.Overwrite,
+        mode = SaveMode.Append,
         options = Map("dataSchema" -> dataSchema.json),
         partitionColumns = Seq("p1"))
     }
 
     // Using different order of partition columns
-    intercept[IllegalArgumentException] {
+    intercept[Throwable] {
       partitionedTestDF2.saveAsTable(
         tableName = "t",
         source = classOf[SimpleTextSource].getCanonicalName,
-        mode = SaveMode.Overwrite,
+        mode = SaveMode.Append,
         options = Map("dataSchema" -> dataSchema.json),
         partitionColumns = Seq("p2", "p1"))
     }

sql/hive/src/test/scala/org/apache/spark/sql/sources/SimpleTextRelation.scala

@@ -92,10 +92,10 @@ class SimpleTextOutputWriter extends OutputWriter {
 class SimpleTextRelation(
     paths: Array[String],
     val maybeDataSchema: Option[StructType],
-    val partitionColumns: StructType,
+    partitionsSchema: StructType,
     parameters: Map[String, String])(
     @transient val sqlContext: SQLContext)
-  extends FSBasedRelation(paths, partitionColumns) {
+  extends FSBasedRelation(paths, partitionsSchema) {
 
   import sqlContext.sparkContext
 
@@ -106,7 +106,8 @@ class SimpleTextRelation(
     case that: SimpleTextRelation =>
       this.paths.sameElements(that.paths) &&
         this.maybeDataSchema == that.maybeDataSchema &&
-        this.dataSchema == that.dataSchema
+        this.dataSchema == that.dataSchema &&
+        this.partitionColumns == that.partitionColumns
 
     case _ => false
   }