add InitSessionVariable in session manager

Author: jennifersp

server/context.go

@@ -235,6 +235,15 @@ func (s *SessionManager) getOrCreateSession(ctx context.Context, conn *mysql.Con
 	return sess, nil
 }
 
+// InitSessionVariable sets a value to a parameter of a session at start.
+func (s *SessionManager) InitSessionVariable(ctx context.Context, conn *mysql.Conn, name, value string) error {
+	sess, err := s.getOrCreateSession(ctx, conn)
+	if err != nil {
+		return err
+	}
+	return sess.InitSessionVariable(s.ctxFactory(ctx, sql.WithSession(sess)), name, value)
+}
+
 // NewContextWithQuery creates a new context for the session at the given conn.
 func (s *SessionManager) NewContextWithQuery(ctx context.Context, conn *mysql.Conn, query string) (*sql.Context, error) {
 	sess, err := s.getOrCreateSession(ctx, conn)