[SPARK-13698][SQL] Fix Analysis Exceptions when Using Backticks in Generate

## What changes were proposed in this pull request?
Analysis exception occurs while running the following query.
```
SELECT ints FROM nestedArray LATERAL VIEW explode(a.b) `a` AS `ints`
```
```
Failed to analyze query: org.apache.spark.sql.AnalysisException: cannot resolve '`ints`' given input columns: [a, `ints`]; line 1 pos 7
'Project ['ints]
+- Generate explode(a#0.b), true, false, Some(a), [`ints`#8]
   +- SubqueryAlias nestedarray
      +- LocalRelation [a#0], [[[[1,2,3]]]]
```

## How was this patch tested?

Added new unit tests in SQLQuerySuite and HiveQlSuite

Author: Dilip Biswal <dbiswal@us.ibm.com>

Closes #11538 from dilipbiswal/SPARK-13698.

1 files changed, 8 insertions, 2 deletions

diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/parser/CatalystQl.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/parser/CatalystQl.scala
index 5d96d8e192..b1b449a0b3 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/parser/CatalystQl.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/parser/CatalystQl.scala
@@ -899,10 +899,16 @@ https://cwiki.apache.org/confluence/display/Hive/Enhanced+Aggregation%2C+Cube%2C
     }
 
     val attributes = clauses.collect {
-      case Token(a, Nil) => UnresolvedAttribute(a.toLowerCase)
+      case Token(a, Nil) => UnresolvedAttribute(cleanIdentifier(a.toLowerCase))
     }
 
-    Generate(generator, join = true, outer = outer, Some(alias.toLowerCase), attributes, child)
+    Generate(
+      generator,
+      join = true,
+      outer = outer,
+      Some(cleanIdentifier(alias.toLowerCase)),
+      attributes,
+      child)
   }
 
   protected def nodeToGenerator(node: ASTNode): Generator = noParseRule("Generator", node)