[SPARK-6145][SQL] fix ORDER BY on nested fields

Based on #4904 with style errors fixed.

`LogicalPlan#resolve` will not only produce `Attribute`, but also "`GetField` chain".
So in `ResolveSortReferences`, after resolve the ordering expressions, we should not just collect the `Attribute` results, but also `Attribute` at the bottom of "`GetField` chain".

Author: Wenchen Fan <cloud0fan@outlook.com>
Author: Michael Armbrust <michael@databricks.com>

Closes #4918 from marmbrus/pr/4904 and squashes the following commits:

997f84e [Michael Armbrust] fix style
3eedbfc [Wenchen Fan] fix 6145

3 files changed, 14 insertions, 3 deletions

diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/SqlParser.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/SqlParser.scala
index c363a5efac..54ab13ca35 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/SqlParser.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/SqlParser.scala
@@ -385,7 +385,7 @@ class SqlParser extends AbstractSparkSQLParser {
 
   protected lazy val dotExpressionHeader: Parser[Expression] =
     (ident <~ ".") ~ ident ~ rep("." ~> ident) ^^ {
-      case i1 ~ i2 ~ rest => UnresolvedAttribute(i1 + "." + i2 + rest.mkString(".", ".", ""))
+      case i1 ~ i2 ~ rest => UnresolvedAttribute((Seq(i1, i2) ++ rest).mkString("."))
     }
 
   protected lazy val dataType: Parser[DataType] =
diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/Analyzer.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/Analyzer.scala
index e4e542562f..7753331748 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/Analyzer.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/Analyzer.scala
@@ -310,7 +310,7 @@ class Analyzer(catalog: Catalog,
   }
 
   /**
-   * In many dialects of SQL is it valid to sort by attributes that are not present in the SELECT
+   * In many dialects of SQL it is valid to sort by attributes that are not present in the SELECT
    * clause.  This rule detects such queries and adds the required attributes to the original
    * projection, so that they will be available during sorting. Another projection is added to
    * remove these attributes after sorting.
@@ -321,7 +321,8 @@ class Analyzer(catalog: Catalog,
           if !s.resolved && p.resolved =>
         val unresolved = ordering.flatMap(_.collect { case UnresolvedAttribute(name) => name })
         val resolved = unresolved.flatMap(child.resolve(_, resolver))
-        val requiredAttributes = AttributeSet(resolved.collect { case a: Attribute => a })
+        val requiredAttributes =
+          AttributeSet(resolved.flatMap(_.collect { case a: Attribute => a }))
 
         val missingInProject = requiredAttributes -- p.output
         if (missingInProject.nonEmpty) {
diff --git a/sql/core/src/test/scala/org/apache/spark/sql/SQLQuerySuite.scala b/sql/core/src/test/scala/org/apache/spark/sql/SQLQuerySuite.scala
index 097bf0dd23..4dedcd365f 100644
--- a/sql/core/src/test/scala/org/apache/spark/sql/SQLQuerySuite.scala
+++ b/sql/core/src/test/scala/org/apache/spark/sql/SQLQuerySuite.scala
@@ -1049,4 +1049,14 @@ class SQLQuerySuite extends QueryTest with BeforeAndAfterAll {
     rdd.toDF().registerTempTable("distinctData")
     checkAnswer(sql("SELECT COUNT(DISTINCT key,value) FROM distinctData"), Row(2))
   }
+
+  test("SPARK-6145: ORDER BY test for nested fields") {
+    jsonRDD(sparkContext.makeRDD(
+      """{"a": {"b": 1, "a": {"a": 1}}, "c": [{"d": 1}]}""" :: Nil)).registerTempTable("nestedOrder")
+    // These should be successfully analyzed
+    sql("SELECT 1 FROM nestedOrder ORDER BY a.b").queryExecution.analyzed
+    sql("SELECT a.b FROM nestedOrder ORDER BY a.b").queryExecution.analyzed
+    sql("SELECT 1 FROM nestedOrder ORDER BY a.a.a").queryExecution.analyzed
+    sql("SELECT 1 FROM nestedOrder ORDER BY c[0].d").queryExecution.analyzed
+  }
 }