add doc

apache · Nov 2, 2016 · ababaa9 · ababaa9
1 parent 553c6a5
commit ababaa9
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Showing 3 changed files with 13 additions and 4 deletions.
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
@@ -275,13 +275,22 @@ trait Nondeterministic extends Expression {
   @transient
   private[this] var initialized = false
 
+  /**
+   * Initializes internal states given the current partition index and mark this as initialized.
+   * Subclasses should override [[initializeInternal()]].
+   */
   final def initialize(partitionIndex: Int): Unit = {
     initializeInternal(partitionIndex)
     initialized = true
   }
 
   protected def initializeInternal(partitionIndex: Int): Unit
 
+  /**
+   * @inheritdoc
+   * Throws an exception if [[initialize()]] is not called yet.
+   * Subclasses should override [[evalInternal()]].
+   */
   final override def eval(input: InternalRow = null): Any = {
     require(initialized,
       s"Nondeterministic expression ${this.getClass.getName} should be initialized before eval.")

diff --git a/.../src/main/scala/org/apache/spark/sql/catalyst/expressions/codegen/GeneratePredicate.scala b/.../src/main/scala/org/apache/spark/sql/catalyst/expressions/codegen/GeneratePredicate.scala
@@ -27,8 +27,8 @@ abstract class Predicate {
   def eval(r: InternalRow): Boolean
 
   /**
-   * Initialize internal states given the current partition index.
-   * This is used by non-deterministic expressions to set initial states.
+   * Initializes internal states given the current partition index.
+   * This is used by nondeterministic expressions to set initial states.
    * The default implementation does nothing.
    */
   def initialize(partitionIndex: Int): Unit = {}

diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/package.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/package.scala
@@ -67,8 +67,8 @@ package object expressions  {
   abstract class Projection extends (InternalRow => InternalRow) {
 
     /**
-     * Initialize internal states given the current partition index.
-     * This is used by non-deterministic expressions to set initial states.
+     * Initializes internal states given the current partition index.
+     * This is used by nondeterministic expressions to set initial states.
      * The default implementation does nothing.
      */
     def initialize(partitionIndex: Int): Unit = {}