[DOCS] Docs-only improvements

…adoc

## What changes were proposed in this pull request?

Use recommended values for row boundaries in Window's scaladoc, i.e. `Window.unboundedPreceding`, `Window.unboundedFollowing`, and `Window.currentRow` (that were introduced in 2.1.0).

## How was this patch tested?

Local build

Author: Jacek Laskowski <jacek@japila.pl>

Closes #17417 from jaceklaskowski/window-expression-scaladoc.

9 files changed, 16 insertions, 14 deletions

diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/ResolveHints.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/ResolveHints.scala
index 70438eb591..920033a9a8 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/ResolveHints.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/ResolveHints.scala
@@ -26,7 +26,7 @@ import org.apache.spark.sql.catalyst.trees.CurrentOrigin
 /**
  * Collection of rules related to hints. The only hint currently available is broadcast join hint.
  *
- * Note that this is separatedly into two rules because in the future we might introduce new hint
+ * Note that this is separately into two rules because in the future we might introduce new hint
  * rules that have different ordering requirements from broadcast.
  */
 object ResolveHints {
diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/encoders/ExpressionEncoder.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/encoders/ExpressionEncoder.scala
index 93fc565a53..ec003cdc17 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/encoders/ExpressionEncoder.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/encoders/ExpressionEncoder.scala
@@ -229,9 +229,9 @@ case class ExpressionEncoder[T](
   // serializer expressions are used to encode an object to a row, while the object is usually an
   // intermediate value produced inside an operator, not from the output of the child operator. This
   // is quite different from normal expressions, and `AttributeReference` doesn't work here
-  // (intermediate value is not an attribute). We assume that all serializer expressions use a same
-  // `BoundReference` to refer to the object, and throw exception if they don't.
-  assert(serializer.forall(_.references.isEmpty), "serializer cannot reference to any attributes.")
+  // (intermediate value is not an attribute). We assume that all serializer expressions use the
+  // same `BoundReference` to refer to the object, and throw exception if they don't.
+  assert(serializer.forall(_.references.isEmpty), "serializer cannot reference any attributes.")
   assert(serializer.flatMap { ser =>
     val boundRefs = ser.collect { case b: BoundReference => b }
     assert(boundRefs.nonEmpty,
diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/Expression.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/Expression.scala
index b93a5d0b7a..1db26d9c41 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/Expression.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/Expression.scala
@@ -491,7 +491,7 @@ abstract class BinaryExpression extends Expression {
  * A [[BinaryExpression]] that is an operator, with two properties:
  *
  * 1. The string representation is "x symbol y", rather than "funcName(x, y)".
- * 2. Two inputs are expected to the be same type. If the two inputs have different types,
+ * 2. Two inputs are expected to be of the same type. If the two inputs have different types,
  *    the analyzer will find the tightest common type and do the proper type casting.
  */
 abstract class BinaryOperator extends BinaryExpression with ExpectsInputTypes {
diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/windowExpressions.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/windowExpressions.scala
index 07d294b108..b2a3888ff7 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/windowExpressions.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/windowExpressions.scala
@@ -695,7 +695,7 @@ case class DenseRank(children: Seq[Expression]) extends RankLike {
  *
  * This documentation has been based upon similar documentation for the Hive and Presto projects.
  *
- * @param children to base the rank on; a change in the value of one the children will trigger a
+ * @param children to base the rank on; a change in the value of one of the children will trigger a
  *                 change in rank. This is an internal parameter and will be assigned by the
  *                 Analyser.
  */
diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/objects.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/objects.scala
index 174d546e22..257dbfac8c 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/objects.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/objects.scala
@@ -65,7 +65,7 @@ object EliminateSerialization extends Rule[LogicalPlan] {
 
 /**
  * Combines two adjacent [[TypedFilter]]s, which operate on same type object in condition, into one,
- * mering the filter functions into one conjunctive function.
+ * merging the filter functions into one conjunctive function.
  */
 object CombineTypedFilters extends Rule[LogicalPlan] {
   def apply(plan: LogicalPlan): LogicalPlan = plan transform {
diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/parser/AstBuilder.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/parser/AstBuilder.scala
index cd238e05d4..162051a8c0 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/parser/AstBuilder.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/parser/AstBuilder.scala
@@ -492,7 +492,7 @@ class AstBuilder extends SqlBaseBaseVisitor[AnyRef] with Logging {
   }
 
   /**
-   * Add an [[Aggregate]] to a logical plan.
+   * Add an [[Aggregate]] or [[GroupingSets]] to a logical plan.
    */
   private def withAggregation(
       ctx: AggregationContext,
@@ -519,7 +519,7 @@ class AstBuilder extends SqlBaseBaseVisitor[AnyRef] with Logging {
   }
 
   /**
-   * Add a Hint to a logical plan.
+   * Add a [[Hint]] to a logical plan.
    */
   private def withHints(
       ctx: HintContext,
@@ -545,7 +545,7 @@ class AstBuilder extends SqlBaseBaseVisitor[AnyRef] with Logging {
   }
 
   /**
-   * Create a single relation referenced in a FROM claused. This method is used when a part of the
+   * Create a single relation referenced in a FROM clause. This method is used when a part of the
    * join condition is nested, for example:
    * {{{
    *   select * from t1 join (t2 cross join t3) on col1 = col2
diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/plans/QueryPlan.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/plans/QueryPlan.scala
index 9fd95a4b36..2d8ec2053a 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/plans/QueryPlan.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/plans/QueryPlan.scala
@@ -230,14 +230,15 @@ abstract class QueryPlan[PlanType <: QueryPlan[PlanType]] extends TreeNode[PlanT
   def producedAttributes: AttributeSet = AttributeSet.empty
 
   /**
-   * Attributes that are referenced by expressions but not provided by this nodes children.
+   * Attributes that are referenced by expressions but not provided by this node's children.
    * Subclasses should override this method if they produce attributes internally as it is used by
    * assertions designed to prevent the construction of invalid plans.
    */
   def missingInput: AttributeSet = references -- inputSet -- producedAttributes
 
   /**
-   * Runs [[transform]] with `rule` on all expressions present in this query operator.
+   * Runs [[transformExpressionsDown]] with `rule` on all expressions present
+   * in this query operator.
    * Users should not expect a specific directionality. If a specific directionality is needed,
    * transformExpressionsDown or transformExpressionsUp should be used.
    *
diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/plans/logical/LogicalPlan.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/plans/logical/LogicalPlan.scala
index e22b429aec..f71a976bd7 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/plans/logical/LogicalPlan.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/plans/logical/LogicalPlan.scala
@@ -32,7 +32,7 @@ abstract class LogicalPlan extends QueryPlan[LogicalPlan] with Logging {
   private var _analyzed: Boolean = false
 
   /**
-   * Marks this plan as already analyzed.  This should only be called by CheckAnalysis.
+   * Marks this plan as already analyzed. This should only be called by [[CheckAnalysis]].
    */
   private[catalyst] def setAnalyzed(): Unit = { _analyzed = true }
 
diff --git a/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/parser/ExpressionParserSuite.scala b/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/parser/ExpressionParserSuite.scala
index c2e62e7397..d1c6b50536 100644
--- a/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/parser/ExpressionParserSuite.scala
+++ b/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/parser/ExpressionParserSuite.scala
@@ -26,7 +26,8 @@ import org.apache.spark.sql.types._
 import org.apache.spark.unsafe.types.CalendarInterval
 
 /**
- * Test basic expression parsing. If a type of expression is supported it should be tested here.
+ * Test basic expression parsing.
+ * If the type of an expression is supported it should be tested here.
  *
  * Please note that some of the expressions test don't have to be sound expressions, only their
  * structure needs to be valid. Unsound expressions should be caught by the Analyzer or