allisonwang-db commented on code in PR #41316:
URL: https://github.com/apache/spark/pull/41316#discussion_r1223912761


##########
sql/core/src/main/scala/org/apache/spark/sql/execution/python/BatchEvalPythonUDTFExec.scala:
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@@ -0,0 +1,163 @@
+/*
+ * 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.python
+
+import java.io.File
+
+import scala.collection.JavaConverters._
+import scala.collection.mutable.ArrayBuffer
+
+import net.razorvine.pickle.Unpickler
+
+import org.apache.spark.{ContextAwareIterator, SparkEnv, TaskContext}
+import org.apache.spark.api.python.{ChainedPythonFunctions, PythonEvalType}
+import org.apache.spark.rdd.RDD
+import org.apache.spark.sql.catalyst.InternalRow
+import org.apache.spark.sql.catalyst.expressions._
+import org.apache.spark.sql.catalyst.util.GenericArrayData
+import org.apache.spark.sql.execution.{SparkPlan, UnaryExecNode}
+import org.apache.spark.sql.types.{DataType, StructField, StructType}
+import org.apache.spark.util.Utils
+
+/**
+ * A physical plan that evaluates a [[PythonUDTF]]. This is similar to 
[[BatchEvalPythonExec]].
+ *
+ * @param udtf the user-defined Python function
+ * @param requiredChildOutput the required output of the child plan. It's used 
for omitting data
+ *                            generation that will be discarded next by a 
projection.
+ * @param resultAttrs the output schema of the Python UDTF.
+ * @param child the child plan
+ */
+case class BatchEvalPythonUDTFExec(
+    udtf: PythonUDTF,
+    requiredChildOutput: Seq[Attribute],
+    resultAttrs: Seq[Attribute],
+    child: SparkPlan)
+  extends UnaryExecNode with PythonSQLMetrics {
+
+  override def output: Seq[Attribute] = requiredChildOutput ++ resultAttrs
+
+  override def producedAttributes: AttributeSet = AttributeSet(resultAttrs)
+
+  protected override def doExecute(): RDD[InternalRow] = {
+    val inputRDD = child.execute().map(_.copy())
+
+    inputRDD.mapPartitions { iter =>
+      val context = TaskContext.get()
+      val contextAwareIterator = new ContextAwareIterator(context, iter)
+
+      // The queue used to buffer input rows so we can drain it to
+      // combine input with output from Python.
+      val queue = HybridRowQueue(context.taskMemoryManager(),
+        new File(Utils.getLocalDir(SparkEnv.get.conf)), child.output.length)
+      context.addTaskCompletionListener[Unit] { ctx =>
+        queue.close()
+      }
+
+      val inputs = Seq(udtf.children)
+
+      // flatten all the arguments
+      val allInputs = new ArrayBuffer[Expression]
+      val dataTypes = new ArrayBuffer[DataType]
+      val argOffsets = inputs.map { input =>
+        input.map { e =>
+          if (allInputs.exists(_.semanticEquals(e))) {
+            allInputs.indexWhere(_.semanticEquals(e))
+          } else {
+            allInputs += e
+            dataTypes += e.dataType
+            allInputs.length - 1
+          }
+        }.toArray
+      }.toArray
+      val projection = MutableProjection.create(allInputs.toSeq, child.output)
+      projection.initialize(context.partitionId())
+      val schema = StructType(dataTypes.zipWithIndex.map { case (dt, i) =>
+        StructField(s"_$i", dt)
+      }.toArray)
+
+      // Add rows to the queue to join later with the result.
+      // Also keep track of the number rows added to the queue.
+      var count = 0L
+      val projectedRowIter = contextAwareIterator.map { inputRow =>
+        queue.add(inputRow.asInstanceOf[UnsafeRow])
+        count += 1
+        projection(inputRow)
+      }
+
+      val outputRowIterator = evaluate(udtf, argOffsets, projectedRowIter, 
schema, context)
+
+      val pruneChildForResult: InternalRow => InternalRow =
+        if (child.outputSet == AttributeSet(requiredChildOutput)) {
+          identity
+        } else {
+          UnsafeProjection.create(requiredChildOutput, child.output)
+        }
+
+      val joined = new JoinedRow
+      val resultProj = UnsafeProjection.create(output, output)
+
+      outputRowIterator.flatMap { outputRows =>
+        if (count > 0) {
+          val left = queue.remove()
+          count -= 1
+          joined.withLeft(pruneChildForResult(left))
+        }
+        outputRows.map(r => resultProj(joined.withRight(r)))
+      }

Review Comment:
   To allow `terminate` to yield more rows, we need to keep track of the number 
of elements in the queue, and when there are no more input rows, we join the 
rows generated by `terminate` with the last input row from a partition (same as 
how Hive UDTFs). 
   I am using a counter here to see if all input rows have been consumed.
   cc @cloud-fan @HyukjinKwon please let me know if there are better ways to do 
this.



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