[SPARK-3483][SQL] Special chars in column names

Supporting special chars in column names by using back ticks. Closed https://github.com/apache/spark/pull/2804 and created this PR as it has merge conflicts

Author: ravipesala <ravindra.pesala@huawei.com>

Closes #2927 from ravipesala/SPARK-3483-NEW and squashes the following commits:

f6329f3 [ravipesala] Rebased with master

2 files changed, 8 insertions, 0 deletions

diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/SparkSQLParser.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/SparkSQLParser.scala
index 04467342e6..219322c015 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/SparkSQLParser.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/SparkSQLParser.scala
@@ -75,6 +75,8 @@ class SqlLexical(val keywords: Seq[String]) extends StdLexical {
       { case chars => StringLit(chars mkString "") }
     | '"' ~> chrExcept('"', '\n', EofCh).* <~ '"' ^^
       { case chars => StringLit(chars mkString "") }
+    | '`' ~> chrExcept('`', '\n', EofCh).* <~ '`' ^^
+      { case chars => Identifier(chars mkString "") }
     | EofCh ^^^ EOF
     | '\'' ~> failure("unclosed string literal")
     | '"' ~> failure("unclosed string literal")
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 3959925a2e..ffb504b949 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
@@ -748,4 +748,10 @@ class SQLQuerySuite extends QueryTest with BeforeAndAfterAll {
         """.stripMargin),
       (1 to 100).map(i => Seq(i, i, i)))
   }
+
+  test("SPARK-3483 Special chars in column names") {
+    val data = sparkContext.parallelize(Seq("""{"key?number1": "value1", "key.number2": "value2"}"""))
+    jsonRDD(data).registerTempTable("records")
+    sql("SELECT `key?number1` FROM records")
+  }
 }