Latihan Lock

Transaksi - BEGIN transaksi COMMIT; - ROLLBACK; (utk membatalkan)

Transaksi buatlah tabel rekening dan isikan datanya CREATE TABLE rekening (norek char(10) PRIMARY KEY, nama varchar(30), saldo numeric(10.2)); DESCRIBE mhs; INSERT INTO rekening VALUES (‘111’,’Bapak’,5000000); INSERT INTO rekening VALUES (‘222’,’anak’,1000000); SELECT * FROM rekening; buatlah transaksi transfer uang 1 juta dari Bapak ke anak

Transaksi Jawaban: BEGIN; UPDATE rekening SET saldo=saldo-1000000 WHERE nama=‘Bapak’;UPDATE rekening SET saldo=saldo+1000000 WHERE nama=‘anak’; COMMIT; Latihan: UPDATE rekening SET saldo=saldo-1000000 WHERE nama=‘Bapak’; ROLLBACK;

A mysql> CREATE TABLE t (i INT) ENGINE = InnoDB; Query OK, 0 rows affected (1.07 sec) mysql> INSERT INTO t (i) VALUES(1); Query OK, 1 row affected (0.09 sec) mysql> START TRANSACTION; Query OK, 0 rows affected (0.00 sec) mysql> SELECT * FROM t WHERE i = 1 LOCK IN SHARE MODE; 1 row in set (0.10 sec)

B mysql> START TRANSACTION; Query OK, 0 rows affected (0.00 sec) mysql> DELETE FROM t WHERE i = 1;

A mysql> DELETE FROM t WHERE i = 1; ERROR 1213 (40001): Deadlock found when trying to get lock; try restarting transaction Sama-sama minta exclusive lock jadi deadlock

Consistent Read

A mysql> BEGIN; Query OK, 0 rows affected (0.00 sec) mysql> SELECT MAX(i) FROM t; mysql> INSERT INTO t(i) VALUES (4); Query OK, 1 row affected (0.00 sec)

B mysql> BEGIN; Query OK, 0 rows affected (0.00 sec) mysql> SELECT MAX(i) FROM t; mysql> INSERT INTO t(i) VALUES(4); Query OK, 1 row affected (0.00 sec) mysql> COMMIT; Query OK, 0 rows affected (0.00 sec)

A mysql> COMMIT; Query OK, 0 rows affected (0.00 sec) mysql> SELECT * FROM t;

A mysql> DELETE FROM t WHERE i=4; Query OK, 2 rows affected (0.00 sec) mysql> SELECT * FROM t;

A mysql> SELECT * FROM t; mysql> BEGIN; Query OK, 0 rows affected (0.00 sec) mysql> SELECT MAX(i) FROM t FOR UPDATE; mysql> INSERT INTO t(i) VALUES (4); Query OK, 1 row affected (0.00 sec)

B mysql> SELECT MAX(i) FROM t FOR UPDATE; mysql> COMMIT; Query OK, 0 rows affected (0.00 sec)

B mysql> SELECT MAX(i) FROM t FOR UPDATE; mysql> INSERT INTO t(i) VALUES(5); Query OK, 1 row affected (0.00 sec) mysql> COMMIT; Query OK, 0 rows affected (0.01 sec) mysql> SELECT * FROM t;

READ LOCK A mysql> BEGIN; Query OK, 0 rows affected (0.00 sec) mysql> SELECT MAX(i) FROM t LOCK IN SHARE MODE;

B mysql> UPDATE t SET i = 55 WHERE i=5;

A mysql> COMMIT; Query OK, 0 rows affected (0.00 sec)

B mysql> UPDATE t SET i = 55 WHERE i=5; Query OK, 0 rows affected (6.95 sec) Rows matched: 0 Changed: 0 Warnings: 0 mysql> UPDATE t SET i = 55 WHERE i=5; Query OK, 1 row affected (43.30 sec) Rows matched: 1 Changed: 1 Warnings: 0 mysql> SELECT * FROM t;