解析MySQL存储过程的游标执行过程

CREATE TABLE t (s1 INT, s2 char(100),PRIMARY KEY (s1));
INSERT INTO t values(1,'aaa');
INSERT INTO t values(2,'bbb');
INSERT INTO t values(3,'ccc');
1.
2.
3.
4.

DELIMITER ;;
  CREATE PROCEDURE test_mysql_cursor_loop()
    BEGIN
      declare v_total int default 0; 
      declare i int default 0; 
      declare str1 int;
      declare str2 varchar(255);
      DECLARE stuCursor CURSOR FOR SELECT s1,s2 FROM t;
      select count(s2) into v_total from t;
      OPEN stuCursor;
      stuLoop:LOOP
        IF i = v_total THEN LEAVE stuLoop; end if;
        FETCH stuCursor INTO str1,str2;
          SELECT str1,str2;
          set i = i+1;
      end loop stuLoop;
    END;;
DELIMITER ;
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.

mysql> show PROCEDURE code test_mysql_cursor_loop;
+-----+---------------------------------------------+
| Pos | Instruction                                 |
+-----+---------------------------------------------+
|   0 | set v_total@0 0                             |
|   1 | set i@1 0                                   |
|   2 | set str1@2 NULL                             |
|   3 | set str2@3 NULL                             |
|   4 | cpush stuCursor@0: SELECT s1,s2 FROM t      |
|   5 | stmt "select count(s2) into v_total from t" |
|   6 | copen stuCursor@0                           |
|   7 | jump_if_not 9(9) (i@1 = v_total@0)          |
|   8 | jump 13                                     |
|   9 | cfetch stuCursor@0 str1@2 str2@3            |
|  10 | stmt "SELECT str1,str2"                     |
|  11 | set i@1 (i@1 + 1)                           |
|  12 | jump 7                                      |
|  13 | cclose stuCursor@0                          |
|  14 | cpop 1                                      |
+-----+---------------------------------------------+
15 rows in set (0.00 sec)
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.