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diff --git a/sql/core/src/main/java/org/apache/spark/sql/execution/BufferedRowIterator.java b/sql/core/src/main/java/org/apache/spark/sql/execution/BufferedRowIterator.java
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+/*
+ * 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;
+
+import java.io.IOException;
+import java.util.LinkedList;
+
+import scala.collection.Iterator;
+
+import org.apache.spark.TaskContext;
+import org.apache.spark.sql.catalyst.InternalRow;
+import org.apache.spark.sql.catalyst.expressions.UnsafeRow;
+
+/**
+ * An iterator interface used to pull the output from generated function for multiple operators
+ * (whole stage codegen).
+ */
+public abstract class BufferedRowIterator {
+  protected LinkedList<InternalRow> currentRows = new LinkedList<>();
+  // used when there is no column in output
+  protected UnsafeRow unsafeRow = new UnsafeRow(0);
+  private long startTimeNs = System.nanoTime();
+
+  protected int partitionIndex = -1;
+
+  public boolean hasNext() throws IOException {
+    if (currentRows.isEmpty()) {
+      processNext();
+    }
+    return !currentRows.isEmpty();
+  }
+
+  public InternalRow next() {
+    return currentRows.remove();
+  }
+
+  /**
+   * Returns the elapsed time since this object is created. This object represents a pipeline so
+   * this is a measure of how long the pipeline has been running.
+   */
+  public long durationMs() {
+    return (System.nanoTime() - startTimeNs) / (1000 * 1000);
+  }
+
+  /**
+   * Initializes from array of iterators of InternalRow.
+   */
+  public abstract void init(int index, Iterator<InternalRow>[] iters);
+
+  /**
+   * Append a row to currentRows.
+   */
+  protected void append(InternalRow row) {
+    currentRows.add(row);
+  }
+
+  /**
+   * Returns whether `processNext()` should stop processing next row from `input` or not.
+   *
+   * If it returns true, the caller should exit the loop (return from processNext()).
+   */
+  protected boolean shouldStop() {
+    return !currentRows.isEmpty();
+  }
+
+  /**
+   * Increase the peak execution memory for current task.
+   */
+  protected void incPeakExecutionMemory(long size) {
+    TaskContext.get().taskMetrics().incPeakExecutionMemory(size);
+  }
+
+  /**
+   * Processes the input until have a row as output (currentRow).
+   *
+   * After it's called, if currentRow is still null, it means no more rows left.
+   */
+  protected abstract void processNext() throws IOException;
+}