fix: correctly classify select statements that begin with brackets (googleapis#351)

Co-authored-by: larkee <larkee@users.noreply.github.com>

Author: larkee

google/cloud/spanner_dbapi/parse_utils.py

@@ -145,7 +145,7 @@
 STMT_INSERT = "INSERT"
 
 # Heuristic for identifying statements that don't need to be run as updates.
-RE_NON_UPDATE = re.compile(r"^\s*(SELECT)", re.IGNORECASE)
+RE_NON_UPDATE = re.compile(r"^\W*(SELECT)", re.IGNORECASE)
 
 RE_WITH = re.compile(r"^\s*(WITH)", re.IGNORECASE)
 

tests/unit/spanner_dbapi/test_parse_utils.py

@@ -33,6 +33,7 @@ def test_classify_stmt(self):
  cases = (
  ("SELECT 1", STMT_NON_UPDATING),
  ("SELECT s.SongName FROM Songs AS s", STMT_NON_UPDATING),
+ ("(SELECT s.SongName FROM Songs AS s)", STMT_NON_UPDATING),
  (
  "WITH sq AS (SELECT SchoolID FROM Roster) SELECT * from sq",
  STMT_NON_UPDATING,