added multi-line to single comments

Author: javierivanov

sql/catalyst/src/main/antlr4/org/apache/spark/sql/catalyst/parser/SqlBase.g4

@@ -1814,7 +1814,7 @@ fragment LETTER
     ;
 
 SIMPLE_COMMENT
-    : '--' ~[\r\n]* '\r'? '\n'? -> channel(HIDDEN)
+    : '--' ('\\\n' | ~[\r\n])* '\r'? '\n'? -> channel(HIDDEN)
     ;
 
 BRACKETED_COMMENT

sql/hive-thriftserver/src/test/scala/org/apache/spark/sql/hive/thriftserver/CliSuite.scala

@@ -464,4 +464,14 @@ class CliSuite extends SparkFunSuite with BeforeAndAfterAll with BeforeAndAfterE
         | 2;""".stripMargin -> "testcomment"
     )
   }
+
+  test("SPARK-30049 Should not complain for quotes in commented with multi-lines") {
+    runCliWithin(3.minute)(
+      """SELECT concat('test', 'comment') -- someone's comment here \
+        | comment continues here with single ' quote \
+        | extra ' \
+        |;""".stripMargin -> "testcomment"
+    )
+  }
+
 }