Allow overriding sqlparse.parse() (#545)

Co-authored-by: Maciej Brencz <maciej.brencz@gmail.com>

Author: illes

sql_metadata/parser.py

@@ -134,7 +134,8 @@ def tokens(self) -> List[SQLToken]:  # noqa: C901
         if self._tokens is not None:
             return self._tokens
 
-        parsed = sqlparse.parse(self._query)
+        # allow parser to be overriden
+        parsed = self._parse(self._query)
         tokens = []
         # handle empty queries (#12)
         if not parsed:
@@ -1104,3 +1105,10 @@ def _get_switch_by_create_query(tokens: List[SQLToken], index: int) -> str:
             switch = "CREATEFUNCTION"
 
         return switch
+
+    @staticmethod
+    def _parse(sql: str) -> Tuple[sqlparse.sql.Statement]:
+        """
+        Parse the SQL query using sqlparse library
+        """
+        return sqlparse.parse(sql)