Redis之支持部分事务

事务

　　执行一组命令,按顺序地串行执行而不会被其它命令插入

事务作用

　　一个队列中,一次性、顺序性、排他性的执行一系列命令

事务相关命令以及操作　　

1           discard      # 取消
2           exec         # 执行所有事务块内的命令
3           multi        # 标记一个事务块的开始
4           unwatch   # 取消对所有key的监视
5           watch      # 监视一个或多个key

　　事务的正常操作、放弃操作、全体连坐、冤头债主

 1 # ---------------正常操作-------------------------
 2     127.0.0.1:6379> keys *
 3     (empty list or set)
 4     127.0.0.1:6379> MULTI
 5     OK
 6     127.0.0.1:6379> set k1 v1
 7     QUEUED
 8     127.0.0.1:6379> set k2 v2
 9     QUEUED
10     127.0.0.1:6379> get k2
11     QUEUED
12     127.0.0.1:6379> set k3 v3
13     QUEUED
14     127.0.0.1:6379> EXEC
15     1) OK
16     2) OK
17     3) "v2"
18     4) OK
19     127.0.0.1:6379> keys *
20     1) "k2"
21     2) "k1"
22     3) "k3"
23 # -------------------取消操作------------------
24     127.0.0.1:6379> MULTI
25     OK
26     127.0.0.1:6379> set k1 v1
27     QUEUED
28     127.0.0.1:6379> set k2 22
29     QUEUED
30     127.0.0.1:6379> DISCARD
31     OK
32     127.0.0.1:6379> get k2
33     "v2"
34 # --------------------全体连坐-------------------
35     127.0.0.1:6379> MULTI
36     OK
37     127.0.0.1:6379> set k1 v1
38     QUEUED
39     127.0.0.1:6379> set k2 v2
40     QUEUED
41     127.0.0.1:6379> set k3 v3
42     QUEUED
43     127.0.0.1:6379> getset k3
44     (error) ERR wrong number of arguments for 'getset' command
45     127.0.0.1:6379> set k4 v4
46     QUEUED
47     127.0.0.1:6379> EXEC
48     (error) EXECABORT Transaction discarded because of previous errors.
49     127.0.0.1:6379> get k4
50     (nil)
51     127.0.0.1:6379> set k1 aa
52     OK
53     127.0.0.1:6379> get k1
54     "aa"
55     127.0.0.1:6379> keys *
56     1) "k2"
57     2) "k1"
58     3) "k3"
59 #  ---------------------冤头债主(可以看出支持部分事务)-------------
60     127.0.0.1:6379> MULTI
61     OK
62     127.0.0.1:6379> INCR k1
63     QUEUED
64     127.0.0.1:6379> set k2 22
65     QUEUED
66     127.0.0.1:6379> set k3 33
67     QUEUED
68     127.0.0.1:6379> set k4 44
69     QUEUED
70     127.0.0.1:6379> get k4
71     QUEUED
72     127.0.0.1:6379> EXEC
73     1) (error) ERR value is not an integer or out of range
74     2) OK
75     3) OK
76     4) OK
77     5) "44"
78     127.0.0.1:6379> get k4
79     "44"

　　watch监控　　　　

悲观锁：认为一定有人改整张表锁定并发性差，一致性好
乐观锁：我认为数据不会被修改不锁表保证并发一致性它在一条数据之后加上Version版本号如果现在有两人操作这条数据，那么后提交的人就要从新再数据库拿到之前提交的那个人的版本号做修改之后再提交CAS(Check And Set)

表锁：整张表锁定，并发性极差，一致性好
行锁：缩小范围，只对行进行锁定

　　watch指令类似乐观锁

 1 # 第一个终端
 2 127.0.0.1:6379> keys *
 3 1) "debt"
 4 2) "k1"
 5 3) "k3"
 6 4) "k4"
 7 5) "k2"
 8 6) "balance"
 9 127.0.0.1:6379> set debt 0
10 OK
11 127.0.0.1:6379> set balance 100
12 OK
13 127.0.0.1:6379> WATCH balance
14 OK
15 127.0.0.1:6379> MULTI
16 OK
17 127.0.0.1:6379> DECRBY balance 20
18 QUEUED
19 127.0.0.1:6379> INCRBY debt 20
20 QUEUED
21 127.0.0.1:6379> EXEC
22 1) (integer) 80
23 2) (integer) 20
24 # ---------------------------加锁-----------------------
25 127.0.0.1:6379> WATCH balance
26 OK
27 127.0.0.1:6379> MULTI
28 OK
29 127.0.0.1:6379> DECRBY balance 20
30 QUEUED
31 127.0.0.1:6379> INCRBY debt 20
32 QUEUED
33 127.0.0.1:6379> EXEC
34 (nil)
35 127.0.0.1:6379> get balance
36 "800"
37 127.0.0.1:6379> get debt
38 "20"
39 # --------------------------------unwatch不加锁----------------
40 127.0.0.1:6379> WATCH balance
41 OK
42 127.0.0.1:6379> set balance 500
43 OK
44 127.0.0.1:6379> UNWATCH
45 OK
46 127.0.0.1:6379> WATCH balance
47 OK
48 127.0.0.1:6379> MULTI
49 OK
50 127.0.0.1:6379> set balance 80
51 QUEUED
52 127.0.0.1:6379> set debt 20
53 QUEUED
54 127.0.0.1:6379> EXEC
55 1) OK
56 2) OK
57 
58 # 第二个终端
59 [root@localhost ~]# redis-cli
60 127.0.0.1:6379> keys *
61 1) "debt"
62 2) "k1"
63 3) "k3"
64 4) "k4"
65 5) "k2"
66 6) "balance"
67 127.0.0.1:6379> get debt
68 "20"
69 127.0.0.1:6379> get balance
70 "80"
71 # ------------------------加锁--------------------------
72 127.0.0.1:6379> set balance 800
73 OK
74 127.0.0.1:6379> 
75 # -----------------------不加锁unwatch------------------
76 127.0.0.1:6379> get balance
77 "500"