mysql> select * from test1 where a=2;
+------+------+---------+
| a    | b    | c       |
+------+------+---------+
|    2 |    3 | record2 |
|    2 |    4 | record3 |
+------+------+---------+
2 rows in set (0.00 sec)

mysql> insert into test1 (b,c) values(4,"record3");
ERROR 810 (HY000): Proxy ERROR:sql is too complex,need to send to only noshard table.
    Shard table insert must has field spec

mysql> insert into test1 (a,c) values(4,"record3");
Query OK, 1 row affected (0.01 sec)

mysql> delete from test1;
ERROR 810 (HY000): Proxy ERROR:sql is too complex,need to send to only noshard table.
    Shard table delete/update must have a where clause

mysql> delete from test1 where a=1;
Query OK, 1 row affected (0.01 sec)