[SPARK-33655][SQL] Improve performance of processing FETCH_PRIOR

### What changes were proposed in this pull request?
Currently, when a client requests FETCH_PRIOR to Thriftserver, Thriftserver reiterates from the start position. Because Thriftserver caches a query result with an array when THRIFTSERVER_INCREMENTAL_COLLECT feature is off, FETCH_PRIOR can be implemented without reiterating the result. A trait FeatureIterator is added in order to separate the implementation for iterator and an array. Also, FeatureIterator supports moves cursor with absolute position, which will be useful for the implementation of FETCH_RELATIVE, FETCH_ABSOLUTE.

### Why are the changes needed?
For better performance of Thriftserver.

### Does this PR introduce _any_ user-facing change?
No

### How was this patch tested?
FetchIteratorSuite

Closes #30600 from Dooyoung-Hwang/refactor_with_fetch_iterator.

Authored-by: Dooyoung Hwang <dooyoung.hwang@sk.com>
Signed-off-by: HyukjinKwon <gurwls223@apache.org>

Author: Dooyoung Hwang

sql/hive-thriftserver/src/main/scala/org/apache/spark/sql/hive/thriftserver/FetchIterator.scala

@@ -0,0 +1,107 @@
+/*
+ * 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.hive.thriftserver
+
+private[hive] sealed trait FetchIterator[A] extends Iterator[A] {
+  /**
+   * Begin a fetch block, forward from the current position.
+   * Resets the fetch start offset.
+   */
+  def fetchNext(): Unit
+
+  /**
+   * Begin a fetch block, moving the iterator back by offset from the start of the previous fetch
+   * block start.
+   * Resets the fetch start offset.
+   *
+   * @param offset the amount to move a fetch start position toward the prior direction.
+   */
+  def fetchPrior(offset: Long): Unit = fetchAbsolute(getFetchStart - offset)
+
+  /**
+   * Begin a fetch block, moving the iterator to the given position.
+   * Resets the fetch start offset.
+   *
+   * @param pos index to move a position of iterator.
+   */
+  def fetchAbsolute(pos: Long): Unit
+
+  def getFetchStart: Long
+
+  def getPosition: Long
+}
+
+private[hive] class ArrayFetchIterator[A](src: Array[A]) extends FetchIterator[A] {
+  private var fetchStart: Long = 0
+
+  private var position: Long = 0
+
+  override def fetchNext(): Unit = fetchStart = position
+
+  override def fetchAbsolute(pos: Long): Unit = {
+    position = (pos max 0) min src.length
+    fetchStart = position
+  }
+
+  override def getFetchStart: Long = fetchStart
+
+  override def getPosition: Long = position
+
+  override def hasNext: Boolean = position < src.length
+
+  override def next(): A = {
+    position += 1
+    src(position.toInt - 1)
+  }
+}
+
+private[hive] class IterableFetchIterator[A](iterable: Iterable[A]) extends FetchIterator[A] {
+  private var iter: Iterator[A] = iterable.iterator
+
+  private var fetchStart: Long = 0
+
+  private var position: Long = 0
+
+  override def fetchNext(): Unit = fetchStart = position
+
+  override def fetchAbsolute(pos: Long): Unit = {
+    val newPos = pos max 0
+    if (newPos < position) resetPosition()
+    while (position < newPos && hasNext) next()
+    fetchStart = position
+  }
+
+  override def getFetchStart: Long = fetchStart
+
+  override def getPosition: Long = position
+
+  override def hasNext: Boolean = iter.hasNext
+
+  override def next(): A = {
+    position += 1
+    iter.next()
+  }
+
+  private def resetPosition(): Unit = {
+    if (position != 0) {
+      iter = iterable.iterator
+      position = 0
+      fetchStart = 0
+    }
+  }
+}

sql/hive-thriftserver/src/main/scala/org/apache/spark/sql/hive/thriftserver/SparkExecuteStatementOperation.scala

@@ -69,13 +69,7 @@ private[hive] class SparkExecuteStatementOperation(
 
   private var result: DataFrame = _
 
-  // We cache the returned rows to get iterators again in case the user wants to use FETCH_FIRST.
-  // This is only used when `spark.sql.thriftServer.incrementalCollect` is set to `false`.
-  // In case of `true`, this will be `None` and FETCH_FIRST will trigger re-execution.
-  private var resultList: Option[Array[SparkRow]] = _
-  private var previousFetchEndOffset: Long = 0
-  private var previousFetchStartOffset: Long = 0
-  private var iter: Iterator[SparkRow] = _
+  private var iter: FetchIterator[SparkRow] = _
   private var dataTypes: Array[DataType] = _
 
   private lazy val resultSchema: TableSchema = {
@@ -148,43 +142,14 @@ private[hive] class SparkExecuteStatementOperation(
     setHasResultSet(true)
     val resultRowSet: RowSet = RowSetFactory.create(getResultSetSchema, getProtocolVersion, false)
 
-    // Reset iter when FETCH_FIRST or FETCH_PRIOR
-    if ((order.equals(FetchOrientation.FETCH_FIRST) ||
-        order.equals(FetchOrientation.FETCH_PRIOR)) && previousFetchEndOffset != 0) {
-      // Reset the iterator to the beginning of the query.
-      iter = if (sqlContext.getConf(SQLConf.THRIFTSERVER_INCREMENTAL_COLLECT.key).toBoolean) {
-        resultList = None
-        result.toLocalIterator.asScala
-      } else {
-        if (resultList.isEmpty) {
-          resultList = Some(result.collect())
-        }
-        resultList.get.iterator
-      }
-    }
-
-    var resultOffset = {
-      if (order.equals(FetchOrientation.FETCH_FIRST)) {
-        logInfo(s"FETCH_FIRST request with $statementId. Resetting to resultOffset=0")
-        0
-      } else if (order.equals(FetchOrientation.FETCH_PRIOR)) {
-        // TODO: FETCH_PRIOR should be handled more efficiently than rewinding to beginning and
-        // reiterating.
-        val targetOffset = math.max(previousFetchStartOffset - maxRowsL, 0)
-        logInfo(s"FETCH_PRIOR request with $statementId. Resetting to resultOffset=$targetOffset")
-        var off = 0
-        while (off < targetOffset && iter.hasNext) {
-          iter.next()
-          off += 1
-        }
-        off
-      } else { // FETCH_NEXT
-        previousFetchEndOffset
-      }
+    if (order.equals(FetchOrientation.FETCH_FIRST)) {
+      iter.fetchAbsolute(0)
+    } else if (order.equals(FetchOrientation.FETCH_PRIOR)) {
+      iter.fetchPrior(maxRowsL)
+    } else {
+      iter.fetchNext()
     }
-
-    resultRowSet.setStartOffset(resultOffset)
-    previousFetchStartOffset = resultOffset
+    resultRowSet.setStartOffset(iter.getPosition)
     if (!iter.hasNext) {
       resultRowSet
     } else {
@@ -206,11 +171,9 @@ private[hive] class SparkExecuteStatementOperation(
         }
         resultRowSet.addRow(row.toArray.asInstanceOf[Array[Object]])
         curRow += 1
-        resultOffset += 1
       }
-      previousFetchEndOffset = resultOffset
       log.info(s"Returning result set with ${curRow} rows from offsets " +
-        s"[$previousFetchStartOffset, $previousFetchEndOffset) with $statementId")
+        s"[${iter.getFetchStart}, ${iter.getPosition}) with $statementId")
       resultRowSet
     }
   }
@@ -326,14 +289,12 @@ private[hive] class SparkExecuteStatementOperation(
       logDebug(result.queryExecution.toString())
       HiveThriftServer2.eventManager.onStatementParsed(statementId,
         result.queryExecution.toString())
-      iter = {
-        if (sqlContext.getConf(SQLConf.THRIFTSERVER_INCREMENTAL_COLLECT.key).toBoolean) {
-          resultList = None
-          result.toLocalIterator.asScala
-        } else {
-          resultList = Some(result.collect())
-          resultList.get.iterator
-        }
+      iter = if (sqlContext.getConf(SQLConf.THRIFTSERVER_INCREMENTAL_COLLECT.key).toBoolean) {
+        new IterableFetchIterator[SparkRow](new Iterable[SparkRow] {
+          override def iterator: Iterator[SparkRow] = result.toLocalIterator.asScala
+        })
+      } else {
+        new ArrayFetchIterator[SparkRow](result.collect())
       }
       dataTypes = result.schema.fields.map(_.dataType)
     } catch {

sql/hive-thriftserver/src/test/scala/org/apache/spark/sql/hive/thriftserver/FetchIteratorSuite.scala

@@ -0,0 +1,134 @@
+/*
+ * 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.hive.thriftserver
+
+import org.apache.spark.SparkFunSuite
+
+class FetchIteratorSuite extends SparkFunSuite {
+
+  private def getRows(fetchIter: FetchIterator[Int], maxRowCount: Int): Seq[Int] = {
+    for (_ <- 0 until maxRowCount if fetchIter.hasNext) yield fetchIter.next()
+  }
+
+  test("SPARK-33655: Test fetchNext and fetchPrior") {
+    val testData = 0 until 10
+
+    def iteratorTest(fetchIter: FetchIterator[Int]): Unit = {
+      fetchIter.fetchNext()
+      assert(fetchIter.getFetchStart == 0)
+      assert(fetchIter.getPosition == 0)
+      assertResult(0 until 2)(getRows(fetchIter, 2))
+      assert(fetchIter.getFetchStart == 0)
+      assert(fetchIter.getPosition == 2)
+
+      fetchIter.fetchNext()
+      assert(fetchIter.getFetchStart == 2)
+      assert(fetchIter.getPosition == 2)
+      assertResult(2 until 3)(getRows(fetchIter, 1))
+      assert(fetchIter.getFetchStart == 2)
+      assert(fetchIter.getPosition == 3)
+
+      fetchIter.fetchPrior(2)
+      assert(fetchIter.getFetchStart == 0)
+      assert(fetchIter.getPosition == 0)
+      assertResult(0 until 3)(getRows(fetchIter, 3))
+      assert(fetchIter.getFetchStart == 0)
+      assert(fetchIter.getPosition == 3)
+
+      fetchIter.fetchNext()
+      assert(fetchIter.getFetchStart == 3)
+      assert(fetchIter.getPosition == 3)
+      assertResult(3 until 8)(getRows(fetchIter, 5))
+      assert(fetchIter.getFetchStart == 3)
+      assert(fetchIter.getPosition == 8)
+
+      fetchIter.fetchPrior(2)
+      assert(fetchIter.getFetchStart == 1)
+      assert(fetchIter.getPosition == 1)
+      assertResult(1 until 4)(getRows(fetchIter, 3))
+      assert(fetchIter.getFetchStart == 1)
+      assert(fetchIter.getPosition == 4)
+
+      fetchIter.fetchNext()
+      assert(fetchIter.getFetchStart == 4)
+      assert(fetchIter.getPosition == 4)
+      assertResult(4 until 10)(getRows(fetchIter, 10))
+      assert(fetchIter.getFetchStart == 4)
+      assert(fetchIter.getPosition == 10)
+
+      fetchIter.fetchNext()
+      assert(fetchIter.getFetchStart == 10)
+      assert(fetchIter.getPosition == 10)
+      assertResult(Seq.empty[Int])(getRows(fetchIter, 10))
+      assert(fetchIter.getFetchStart == 10)
+      assert(fetchIter.getPosition == 10)
+
+      fetchIter.fetchPrior(20)
+      assert(fetchIter.getFetchStart == 0)
+      assert(fetchIter.getPosition == 0)
+      assertResult(0 until 3)(getRows(fetchIter, 3))
+      assert(fetchIter.getFetchStart == 0)
+      assert(fetchIter.getPosition == 3)
+    }
+    iteratorTest(new ArrayFetchIterator[Int](testData.toArray))
+    iteratorTest(new IterableFetchIterator[Int](testData))
+  }
+
+  test("SPARK-33655: Test fetchAbsolute") {
+    val testData = 0 until 10
+
+    def iteratorTest(fetchIter: FetchIterator[Int]): Unit = {
+      fetchIter.fetchNext()
+      assert(fetchIter.getFetchStart == 0)
+      assert(fetchIter.getPosition == 0)
+      assertResult(0 until 5)(getRows(fetchIter, 5))
+      assert(fetchIter.getFetchStart == 0)
+      assert(fetchIter.getPosition == 5)
+
+      fetchIter.fetchAbsolute(2)
+      assert(fetchIter.getFetchStart == 2)
+      assert(fetchIter.getPosition == 2)
+      assertResult(2 until 5)(getRows(fetchIter, 3))
+      assert(fetchIter.getFetchStart == 2)
+      assert(fetchIter.getPosition == 5)
+
+      fetchIter.fetchAbsolute(7)
+      assert(fetchIter.getFetchStart == 7)
+      assert(fetchIter.getPosition == 7)
+      assertResult(7 until 8)(getRows(fetchIter, 1))
+      assert(fetchIter.getFetchStart == 7)
+      assert(fetchIter.getPosition == 8)
+
+      fetchIter.fetchAbsolute(20)
+      assert(fetchIter.getFetchStart == 10)
+      assert(fetchIter.getPosition == 10)
+      assertResult(Seq.empty[Int])(getRows(fetchIter, 1))
+      assert(fetchIter.getFetchStart == 10)
+      assert(fetchIter.getPosition == 10)
+
+      fetchIter.fetchAbsolute(0)
+      assert(fetchIter.getFetchStart == 0)
+      assert(fetchIter.getPosition == 0)
+      assertResult(0 until 3)(getRows(fetchIter, 3))
+      assert(fetchIter.getFetchStart == 0)
+      assert(fetchIter.getPosition == 3)
+    }
+    iteratorTest(new ArrayFetchIterator[Int](testData.toArray))
+    iteratorTest(new IterableFetchIterator[Int](testData))
+  }
+}