[SPARK-15152][DOC][MINOR] Scaladoc and Code style Improvements

## What changes were proposed in this pull request?

Minor doc and code style fixes

## How was this patch tested?

local build

Author: Jacek Laskowski <jacek@japila.pl>

Closes #12928 from jaceklaskowski/SPARK-15152.

7 files changed, 20 insertions, 15 deletions

diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/planning/QueryPlanner.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/planning/QueryPlanner.scala
index 516b41cb13..8b1a34f79c 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/planning/QueryPlanner.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/planning/QueryPlanner.scala
@@ -22,7 +22,7 @@ import org.apache.spark.sql.catalyst.plans.logical.LogicalPlan
 import org.apache.spark.sql.catalyst.trees.TreeNode
 
 /**
- * Given a [[plans.logical.LogicalPlan LogicalPlan]], returns a list of `PhysicalPlan`s that can
+ * Given a [[LogicalPlan]], returns a list of `PhysicalPlan`s that can
  * be used for execution. If this strategy does not apply to the give logical operation then an
  * empty list should be returned.
  */
@@ -31,9 +31,10 @@ abstract class GenericStrategy[PhysicalPlan <: TreeNode[PhysicalPlan]] extends L
 }
 
 /**
- * Abstract class for transforming [[plans.logical.LogicalPlan LogicalPlan]]s into physical plans.
- * Child classes are responsible for specifying a list of [[Strategy]] objects that each of which
- * can return a list of possible physical plan options.  If a given strategy is unable to plan all
+ * Abstract class for transforming [[LogicalPlan]]s into physical plans.
+ * Child classes are responsible for specifying a list of [[GenericStrategy]] objects that
+ * each of which can return a list of possible physical plan options.
+ * If a given strategy is unable to plan all
  * of the remaining operators in the tree, it can call [[planLater]], which returns a placeholder
  * object that will be filled in using other available strategies.
  *
diff --git a/sql/core/src/main/scala/org/apache/spark/sql/execution/ExpandExec.scala b/sql/core/src/main/scala/org/apache/spark/sql/execution/ExpandExec.scala
index c201822d44..1be41ffc07 100644
--- a/sql/core/src/main/scala/org/apache/spark/sql/execution/ExpandExec.scala
+++ b/sql/core/src/main/scala/org/apache/spark/sql/execution/ExpandExec.scala
@@ -26,7 +26,7 @@ import org.apache.spark.sql.catalyst.plans.physical.{Partitioning, UnknownPartit
 import org.apache.spark.sql.execution.metric.SQLMetrics
 
 /**
- * Apply the all of the GroupExpressions to every input row, hence we will get
+ * Apply all of the GroupExpressions to every input row, hence we will get
  * multiple output rows for a input row.
  * @param projections The group of expressions, all of the group expressions should
  *                    output the same schema specified bye the parameter `output`
diff --git a/sql/core/src/main/scala/org/apache/spark/sql/execution/SparkPlan.scala b/sql/core/src/main/scala/org/apache/spark/sql/execution/SparkPlan.scala
index 0bbe970420..b94b84d77a 100644
--- a/sql/core/src/main/scala/org/apache/spark/sql/execution/SparkPlan.scala
+++ b/sql/core/src/main/scala/org/apache/spark/sql/execution/SparkPlan.scala
@@ -106,16 +106,20 @@ abstract class SparkPlan extends QueryPlan[SparkPlan] with Logging with Serializ
   def requiredChildOrdering: Seq[Seq[SortOrder]] = Seq.fill(children.size)(Nil)
 
   /**
-   * Returns the result of this query as an RDD[InternalRow] by delegating to doExecute after
-   * preparations. Concrete implementations of SparkPlan should override doExecute.
+   * Returns the result of this query as an RDD[InternalRow] by delegating to `doExecute` after
+   * preparations.
+   *
+   * Concrete implementations of SparkPlan should override `doExecute`.
    */
   final def execute(): RDD[InternalRow] = executeQuery {
     doExecute()
   }
 
   /**
-   * Returns the result of this query as a broadcast variable by delegating to doBroadcast after
-   * preparations. Concrete implementations of SparkPlan should override doBroadcast.
+   * Returns the result of this query as a broadcast variable by delegating to `doExecuteBroadcast`
+   * after preparations.
+   *
+   * Concrete implementations of SparkPlan should override `doExecuteBroadcast`.
    */
   final def executeBroadcast[T](): broadcast.Broadcast[T] = executeQuery {
     doExecuteBroadcast()
diff --git a/sql/core/src/main/scala/org/apache/spark/sql/execution/WholeStageCodegenExec.scala b/sql/core/src/main/scala/org/apache/spark/sql/execution/WholeStageCodegenExec.scala
index 15b4abe806..d6f7b6ed35 100644
--- a/sql/core/src/main/scala/org/apache/spark/sql/execution/WholeStageCodegenExec.scala
+++ b/sql/core/src/main/scala/org/apache/spark/sql/execution/WholeStageCodegenExec.scala
@@ -105,7 +105,7 @@ trait CodegenSupport extends SparkPlan {
   protected def doProduce(ctx: CodegenContext): String
 
   /**
-   * Consume the generated columns or row from current SparkPlan, call it's parent's doConsume().
+   * Consume the generated columns or row from current SparkPlan, call its parent's `doConsume()`.
    */
   final def consume(ctx: CodegenContext, outputVars: Seq[ExprCode], row: String = null): String = {
     val inputVars =
@@ -212,8 +212,8 @@ trait CodegenSupport extends SparkPlan {
 /**
  * InputAdapter is used to hide a SparkPlan from a subtree that support codegen.
  *
- * This is the leaf node of a tree with WholeStageCodegen, is used to generate code that consumes
- * an RDD iterator of InternalRow.
+ * This is the leaf node of a tree with WholeStageCodegen that is used to generate code
+ * that consumes an RDD iterator of InternalRow.
  */
 case class InputAdapter(child: SparkPlan) extends UnaryExecNode with CodegenSupport {
 
diff --git a/sql/core/src/main/scala/org/apache/spark/sql/execution/objects.scala b/sql/core/src/main/scala/org/apache/spark/sql/execution/objects.scala
index 56a3906951..bafbbdf657 100644
--- a/sql/core/src/main/scala/org/apache/spark/sql/execution/objects.scala
+++ b/sql/core/src/main/scala/org/apache/spark/sql/execution/objects.scala
@@ -158,7 +158,7 @@ case class MapPartitionsExec(
  * Applies the given function to each input object.
  * The output of its child must be a single-field row containing the input object.
  *
- * This operator is kind of a safe version of [[ProjectExec]], as it's output is custom object,
+ * This operator is kind of a safe version of [[ProjectExec]], as its output is custom object,
  * we need to use safe row to contain it.
  */
 case class MapElementsExec(
diff --git a/sql/core/src/main/scala/org/apache/spark/sql/execution/streaming/FileStreamSource.scala b/sql/core/src/main/scala/org/apache/spark/sql/execution/streaming/FileStreamSource.scala
index 8e66538575..7b4c035bf3 100644
--- a/sql/core/src/main/scala/org/apache/spark/sql/execution/streaming/FileStreamSource.scala
+++ b/sql/core/src/main/scala/org/apache/spark/sql/execution/streaming/FileStreamSource.scala
@@ -95,7 +95,7 @@ class FileStreamSource(
     val endId = end.asInstanceOf[LongOffset].offset
 
     assert(startId <= endId)
-    val files = metadataLog.get(Some(startId + 1), Some(endId)).map(_._2).flatten
+    val files = metadataLog.get(Some(startId + 1), Some(endId)).flatMap(_._2)
     logInfo(s"Processing ${files.length} files from ${startId + 1}:$endId")
     logDebug(s"Streaming ${files.mkString(", ")}")
     dataFrameBuilder(files)
diff --git a/sql/core/src/main/scala/org/apache/spark/sql/execution/streaming/IncrementalExecution.scala b/sql/core/src/main/scala/org/apache/spark/sql/execution/streaming/IncrementalExecution.scala
index b89144d727..e9052a3095 100644
--- a/sql/core/src/main/scala/org/apache/spark/sql/execution/streaming/IncrementalExecution.scala
+++ b/sql/core/src/main/scala/org/apache/spark/sql/execution/streaming/IncrementalExecution.scala
@@ -47,7 +47,7 @@ class IncrementalExecution(
 
   /**
    * Records the current id for a given stateful operator in the query plan as the `state`
-   * preperation walks the query plan.
+   * preparation walks the query plan.
    */
   private var operatorId = 0