[SPARK-6114][SQL] Avoid metastore conversions before plan is resolved

Author: Michael Armbrust <michael@databricks.com>

Closes #4855 from marmbrus/explodeBug and squashes the following commits:

a712249 [Michael Armbrust] [SPARK-6114][SQL] Avoid metastore conversions before plan is resolved

sql/hive/src/main/scala/org/apache/spark/sql/hive/HiveMetastoreCatalog.scala

@@ -444,6 +444,10 @@ private[hive] class HiveMetastoreCatalog(hive: HiveContext) extends Catalog with
    */
   object ParquetConversions extends Rule[LogicalPlan] {
     override def apply(plan: LogicalPlan): LogicalPlan = {
+      if (!plan.resolved) {
+        return plan
+      }
+
       // Collects all `MetastoreRelation`s which should be replaced
       val toBeReplaced = plan.collect {
         // Write path

sql/hive/src/test/scala/org/apache/spark/sql/hive/execution/SQLQuerySuite.scala

@@ -31,6 +31,9 @@ case class Nested1(f1: Nested2)
 case class Nested2(f2: Nested3)
 case class Nested3(f3: Int)
 
+case class NestedArray2(b: Seq[Int])
+case class NestedArray1(a: NestedArray2)
+
 /**
  * A collection of hive query tests where we generate the answers ourselves instead of depending on
  * Hive to generate them (in contrast to HiveQuerySuite).  Often this is because the query is
@@ -38,6 +41,13 @@ case class Nested3(f3: Int)
  */
 class SQLQuerySuite extends QueryTest {
 
+  test("explode nested Field") {
+    Seq(NestedArray1(NestedArray2(Seq(1,2,3)))).toDF.registerTempTable("nestedArray")
+    checkAnswer(
+      sql("SELECT ints FROM nestedArray LATERAL VIEW explode(a.b) a AS ints"),
+      Row(1) :: Row(2) :: Row(3) :: Nil)
+  }
+
   test("SPARK-4512 Fix attribute reference resolution error when using SORT BY") {
     checkAnswer(
       sql("SELECT * FROM (SELECT key + key AS a FROM src SORT BY value) t ORDER BY t.a"),