[SPARK-8020] Spark SQL in spark-defaults.conf make metadataHive get constructed too early

sql/core/src/main/scala/org/apache/spark/sql/SQLContext.scala

@@ -182,9 +182,28 @@ class SQLContext(@transient val sparkContext: SparkContext)
     conf.dialect
   }
 
-  sparkContext.getConf.getAll.foreach {
-    case (key, value) if key.startsWith("spark.sql") => setConf(key, value)
-    case _ =>
+  {
+    // We extract spark sql settings from SparkContext's conf and put them to
+    // Spark SQL's conf.
+    // First, we populate the SQLConf (conf). So, we can make sure that other values using
+    // those settings in their construction can get the correct settings.
+    // For example, metadataHive in HiveContext may need both spark.sql.hive.metastore.version
+    // and spark.sql.hive.metastore.jars to get correctly constructed.
+    val properties = new Properties
+    sparkContext.getConf.getAll.foreach {
+      case (key, value) if key.startsWith("spark.sql") => properties.setProperty(key, value)
+      case _ =>
+    }
+    // We directly put those settings to conf to avoid of calling setConf, which may have
+    // side-effects. For example, in HiveContext, setConf may cause executionHive and metadataHive
+    // get constructed. If we call setConf directly, the constructed metadataHive may have
+    // wrong settings, or the construction may fail.
+    conf.setConf(properties)
+    // After we have populated SQLConf, we call setConf to populate other confs in the subclass
+    // (e.g. hiveconf in HiveContext).
+    properties.foreach {
+      case (key, value) => setConf(key, value)
+    }
   }
 
   @transient

sql/hive/src/test/scala/org/apache/spark/sql/hive/client/VersionsSuite.scala

@@ -17,7 +17,8 @@
 
 package org.apache.spark.sql.hive.client
 
-import org.apache.spark.{Logging, SparkFunSuite}
+import org.apache.spark.sql.hive.HiveContext
+import org.apache.spark.{Logging, SparkConf, SparkContext, SparkFunSuite}
 import org.apache.spark.sql.catalyst.util.quietly
 import org.apache.spark.util.Utils
 
@@ -37,6 +38,48 @@ class VersionsSuite extends SparkFunSuite with Logging {
       "hive.metastore.warehouse.dir" -> warehousePath.toString)
   }
 
+  test("SPARK-8020: successfully create a HiveContext with metastore settings in Spark conf.") {
+    val sparkConf =
+      new SparkConf() {
+        // We are not really clone it. We need to keep the custom getAll.
+        override def clone: SparkConf = this
+
+        override def getAll: Array[(String, String)] = {
+          val allSettings = super.getAll
+          val metastoreVersion = get("spark.sql.hive.metastore.version")
+          val metastoreJars = get("spark.sql.hive.metastore.jars")
+
+          val others = allSettings.filterNot { case (key, _) =>
+            key == "spark.sql.hive.metastore.version" || key == "spark.sql.hive.metastore.jars"
+          }
+
+          // Put metastore.version to the first one. It is needed to trigger the exception
+          // caused by SPARK-8020. Other problems triggered by SPARK-8020
+          // (e.g. using Hive 0.13.1's metastore client to connect to the a 0.12 metastore)
+          // are not easy to test.
+          Array(
+            ("spark.sql.hive.metastore.version" -> metastoreVersion),
+            ("spark.sql.hive.metastore.jars" -> metastoreJars)) ++ others
+        }
+      }
+    sparkConf
+      .set("spark.sql.hive.metastore.version", "12")
+      .set("spark.sql.hive.metastore.jars", "maven")
+
+    val hiveContext = new HiveContext(
+      new SparkContext(
+        "local[2]",
+        "TestSQLContextInVersionsSuite",
+        sparkConf)) {
+
+      protected override def configure(): Map[String, String] = buildConf
+
+    }
+
+    // Make sure all metastore related lazy vals got created.
+    hiveContext.tables()
+  }
+
   test("success sanity check") {
     val badClient = IsolatedClientLoader.forVersion("13", buildConf()).client
     val db = new HiveDatabase("default", "")