Redis Transaction and lock applications

Redis supports simple transactions

Comparison of Redis and MySQL transactions

	Mysql	Redis
Open	Start transaction	Muitl
Statement	Normal SQL	General Command
Failed	Rollback rollback	Discard Cancel
Success	Commit	Exec

Note: The difference between rollback and discard

If 2 statements have been executed successfully, the 3rd statement has an error.

After the rollback, the first 2 statements affect the disappearance.

Discard only ends this transaction, the impact of the first 2 statements is still

Note:

In the statement that follows Mutil, there may be 2 cases of error in the statement

1: Grammar is a problem,

This, exec, error, all statements are not executed

2: The syntax itself is correct, but there is a problem with the applicable object. For example, Zadd manipulating the list object

After exec, the correct statements are executed and the inappropriate statements are skipped.

(If Zadd operations list how can this be avoided? This is the programmer's responsibility)

Thinking:

I was buying a ticket.

Ticket-1, money-100

And the ticket only 1, if after I multi, and exec before, the ticket was bought by others---namely ticket becomes 0.

How can I observe this situation and not submit

A pessimistic idea:

The world is full of danger, it must be someone and I rob, to ticket lock, only I can operate. [Pessimistic lock]

An optimistic idea:

Not so people and I rob, therefore, I just need to note that

--No one can change the value of the ticket. [Optimistic lock]

In the Redis transaction, the optimistic lock is enabled and only the monitoring key is not altered.

Specific command----Watch command

Cases:

Redis 127.0.0.1:6379> Watch Ticket

Ok

Redis 127.0.0.1:6379> Multi

Ok

Redis 127.0.0.1:6379> DECR Ticket

QUEUED

Redis 127.0.0.1:6379> Decrby Money 100

QUEUED

Redis 127.0.0.1:6379> exec

(nil)//return nil, indicating that the monitoring ticket has changed and the transaction is canceled.

Redis 127.0.0.1:6379> Get Ticket

"0"

Redis 127.0.0.1:6379> Get Money

"200"

Watch Key1 Key2 ... KeyN

Role: Monitor Key1 key2. Keyn There are no changes, if there is a change, then the transaction is canceled

Unwatch

Function: Cancels all watch monitoring

Redis Transaction and lock applications