Github user andrewor14 commented on a diff in the pull request:
https://github.com/apache/spark/pull/8573#discussion_r39213644
--- Diff:
sql/core/src/main/scala/org/apache/spark/sql/execution/local/TakeOrderedAndProjectNode.scala
---
@@ -0,0 +1,70 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.spark.sql.execution.local
+
+import org.apache.spark.sql.catalyst.InternalRow
+import org.apache.spark.sql.catalyst.expressions._
+import org.apache.spark.util.BoundedPriorityQueue
+
+case class TakeOrderedAndProjectNode(
+ limit: Int,
+ sortOrder: Seq[SortOrder],
+ projectList: Option[Seq[NamedExpression]],
+ child: LocalNode) extends UnaryLocalNode {
+
+ override def output: Seq[Attribute] = {
+ val projectOutput = projectList.map(_.map(_.toAttribute))
+ projectOutput.getOrElse(child.output)
+ }
+
+ private[this] var projection: Option[Projection] = _
+
+ private[this] var ord: InterpretedOrdering = _
+
+ private[this] var iterator: Iterator[InternalRow] = _
+
+ private[this] var currentRow: InternalRow = _
+
+ override def open(): Unit = {
+ child.open()
+ projection = projectList.map(new InterpretedProjection(_,
child.output))
+ ord = new InterpretedOrdering(sortOrder, child.output)
+ val queue = new BoundedPriorityQueue[InternalRow](limit)(ord.reverse)
+ while (child.next()) {
+ queue += child.fetch()
+ }
+ // Close it eagerly since we don't need it.
+ child.close()
+ iterator = queue.iterator
+ }
+
+ override def next(): Boolean = {
+ if (iterator.hasNext) {
+ val _currentRow = iterator.next()
+ currentRow = projection.map(p =>
p(_currentRow)).getOrElse(_currentRow)
--- End diff --
might be easier to read if you just expand this:
```
currentRow = projection match {
case Some(p) => p(_currentRow)
case None => _currentRow
}
```
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