Github user davies commented on a diff in the pull request:
https://github.com/apache/spark/pull/7904#discussion_r36581669
--- Diff:
sql/core/src/main/scala/org/apache/spark/sql/execution/joins/RowIterator.scala
---
@@ -0,0 +1,63 @@
+/*
+ * 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.joins
+
+import java.util.NoSuchElementException
+
+import org.apache.spark.sql.catalyst.InternalRow
+
+private[sql] abstract class RowIterator {
+ def advanceNext(): Boolean
+ def getRow: InternalRow
+ def toScala: Iterator[InternalRow] = new RowIteratorToScala(this)
+}
+
+object RowIterator {
+ def fromScala(scalaIter: Iterator[InternalRow]): RowIterator = {
+ scalaIter match {
+ case wrappedRowIter: RowIteratorToScala => wrappedRowIter.rowIter
+ case _ => new RowIteratorFromScala(scalaIter)
+ }
+ }
+}
+
+private final class RowIteratorToScala(val rowIter: RowIterator) extends
Iterator[InternalRow] {
+ private [this] var _hasNext: Boolean = rowIter.advanceNext()
+ override def hasNext: Boolean = _hasNext
+ override def next(): InternalRow = {
+ if (!_hasNext) throw new NoSuchElementException
+ val row: InternalRow = rowIter.getRow.copy()
--- End diff --
We're moving to let consumer to do the copy, before we check all the
existing usage, I agreed that it's safe to have a copy here.
In this case, the consume of iterator may want to call `hasNext()` before
finish the current row (before return it, as it wants to do some cleanup), in
long term, I think it's better to not do this, or do the copy itself.
Right now, it's safe to have this copy here (we already have this). The
reason I want to raise this question is that, it's really cheap to call
`copy()` on a GenericInternalRow (if it's already copied from MutableRow, it's
read-only now, just return itself), but right now we have UnsafeRow everywhere,
it's not cheap anymore. If we have multiple chained iterator like this, we will
copy multiples times.
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