Github user vanzin commented on a diff in the pull request:
https://github.com/apache/spark/pull/6627#discussion_r32282458
--- Diff:
sql/hive/src/main/scala/org/apache/spark/sql/hive/client/HiveShim.scala ---
@@ -0,0 +1,267 @@
+/*
+ * 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.client
+
+import java.lang.{Boolean => JBoolean, Integer => JInteger}
+import java.lang.reflect.{Method, Modifier}
+import java.net.URI
+import java.util.{ArrayList => JArrayList, List => JList, Map => JMap, Set
=> JSet}
+
+import scala.collection.JavaConversions._
+
+import org.apache.hadoop.fs.Path
+import org.apache.hadoop.hive.conf.HiveConf
+import org.apache.hadoop.hive.ql.Driver
+import org.apache.hadoop.hive.ql.metadata.{Hive, Partition, Table}
+import org.apache.hadoop.hive.ql.processors.{CommandProcessor,
CommandProcessorFactory}
+import org.apache.hadoop.hive.ql.session.SessionState
+
+/**
+ * A shim that defines the interface between ClientWrapper and the
underlying Hive library used to
+ * talk to the metastore. Each Hive version has its own implementation of
this class, defining
+ * version-specific version of needed functions.
+ *
+ * The guideline for writing shims is:
+ * - always extend from the previous version unless really not possible
+ * - initialize methods in lazy vals, both for quicker access for multiple
invocations, and to
+ * avoid runtime errors due to the above guideline.
+ */
+private[client] sealed abstract class Shim {
+
+ def setCurrentSessionState(state: SessionState): Unit
+
+ /**
+ * This shim is necessary because the return type is different on
different versions of Hive.
+ * All parameters are the same, though.
+ */
+ def getDataLocation(table: Table): Option[String]
+
+ def setDataLocation(table: Table, loc: String): Unit
+
+ def getAllPartitions(hive: Hive, table: Table): Seq[Partition]
+
+ def getCommandProcessor(token: String, conf: HiveConf): CommandProcessor
+
+ def getDriverResults(driver: Driver): Seq[String]
+
+ def loadPartition(
+ hive: Hive,
+ loadPath: Path,
+ tableName: String,
+ partSpec: JMap[String, String],
+ replace: Boolean,
+ holdDDLTime: Boolean,
+ inheritTableSpecs: Boolean,
+ isSkewedStoreAsSubdir: Boolean): Unit
+
+ def loadTable(
+ hive: Hive,
+ loadPath: Path,
+ tableName: String,
+ replace: Boolean,
+ holdDDLTime: Boolean): Unit
+
+ def loadDynamicPartitions(
+ hive: Hive,
+ loadPath: Path,
+ tableName: String,
+ partSpec: JMap[String, String],
+ replace: Boolean,
+ numDP: Int,
+ holdDDLTime: Boolean,
+ listBucketingEnabled: Boolean): Unit
+
+ protected def findStaticMethod(klass: Class[_], name: String, args:
Class[_]*): Method = {
+ val method = findMethod(klass, name, args: _*)
+ require(Modifier.isStatic(method.getModifiers()),
+ s"Method $name of class $klass is not static.")
+ method
+ }
+
+ protected def findMethod(klass: Class[_], name: String, args:
Class[_]*): Method = {
+ klass.getMethod(name, args: _*)
+ }
+
+}
+
+private[client] class Shim_v0_12 extends Shim {
+
+ private lazy val startMethod = findStaticMethod(classOf[SessionState],
"start",
--- End diff --
Yes, because otherwise you can't have the shim for the next version extend
this one. I mention this in the scaladoc for the `Shim` class.
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