配置MongoDB副本集

1 案例1：配置MongoDB副本集

1.1 问题

• 具体要求：
• 准备3台mongodb服务器
• 配置副本集服务
• 验证副本集配置

1.2 方案

准备三台虚拟机，配置mongodb副本集，ip分别为192.158.4.51， 192.168.4.52，192.168.4.53其中一个是主节点，负责处理客户端请求，其余的都是从节点，负责复制主节点上的数据，实现存储数据副本，提高了数据的可用性，具体分配如表-1所示：

表-1

1.3 步骤

实现此案例需要按照如下步骤进行。

步骤一：创建mongodb副本集

1）三台主机安装mongodb（以4.51为例）

1. [root@mongodb51 ~]# cd mongodb/
2. [root@mongodb51 mongodb]# mkdir /usr/local/mongodb
3. [root@mongodb51 mongodb]# cd /usr/local/mongodb
4. [root@mongodb51 mongodb]# cp -r \
5. /root/mongodb/mongodb-linux-x86_64-rhel70-3.6.3/bin/ .
6. [root@mongodb51 mongodb]# ls
7. bin
8. [root@mongodb51 mongodb]# mkdir etc
9. [root@mongodb51 mongodb]# mkdir log
10. [root@mongodb51 mongodb]# mkdir -p data/db
11. [root@mongodb51 mongodb]# vim etc/mongodb.conf
12. dbpath=/usr/local/mongodb/data/db/
13. logpath=/usr/local/mongodb/log/mongodb.log
14. logappend=true
15. fork=true
16. bind_ip=192.168.4.51
17. port=27077
18. replSet=rs1        
19. //加入到副本集，rs1名字随便起，想知道谁和我在一个副本集里，三台机器的名字一样,都写rs1

2）设置PATH变量

1. [root@mongodb51 mongodb]# vim /etc/profile
2. export PATH=/usr/local/mongodb/bin:$PATH
3. [root@mongodb51 mongodb]# source /etc/profile

3）由于启动和停止服务名字太长，可以起一个别名

给停止服务起一个别名

1. [root@mongodb51 mongodb]# alias cmdb='mongod --dbpath=/usr/local/mongodb/data/db/ --shutdown'

给启动服务起一个别名

1. [root@mongodb51 mongodb]# alias smdb='mongod -f /usr/local/mongodb/etc/mongodb.conf'

4）启动服务并连接

1. [root@mongodb51 ~]# smdb
2. about to fork child process, waiting until server is ready for connections.
3. forked process: 5656
4. child process started successfully, parent exiting
5. [root@mongodb51 ~]# mongo --host 192.168.4.51 --port 27077
6. MongoDB shell version v3.6.3
7. connecting to: mongodb://192.168.4.51:27077/
8. MongoDB server version: 3.6.3
9. ...
10. >

5）配置集群信息，任意一台都可以，在这里在51上面操作

1. > rs1_config = {        //rs1_config随便起变量名,要记住
2. _id:"rs1",         //必须为rs1这个，三台主机集群名，配置文件里面写的是这个
3. members:[
4. {_id:0,host:"192.168.4.51:27077"},        //_id值随意，host值固定
5. {_id:1,host:"192.168.4.52:27078"},
6. {_id:2,host:"192.168.4.53:27079"}
7. ]
8. };        //回车，出现下面情况为成功
9. {
10.     "_id" : "rs1",
11.     "members" : [
12.         {
13.             "_id" : 0,
14.             "host" : "192.168.4.51:27077"
15.         },
16.         {
17.             "_id" : 1,
18.             "host" : "192.168.4.52:27078"
19.         },
20.         {
21.             "_id" : 2,
22.             "host" : "192.168.4.53:27079"
23.         }
24.     ]
25. }
26. >

6）初始化Replica Sets环境

1. > rs.initiate(rs1_config)
2. {
3.     "ok" : 1,
4.     "operationTime" : Timestamp(1538187475, 1),
5.     "$clusterTime" : {
6.         "clusterTime" : Timestamp(1538187475, 1),
7.         "signature" : {
8.             "hash" : BinData(0,"AAAAAAAAAAAAAAAAAAAAAAAAAAA="),
9.             "keyId" : NumberLong(0)
10.         }
11.     }
12. }
14. rs1:SECONDARY>
15. rs1:PRIMARY>            //提示PRIMARY，51为主

7）在52和53上面查看

1. [root@mongodb52 ~]# mongo --host 192.168.4.52 --port 27078
2. MongoDB shell version v3.6.3
3. connecting to: mongodb://192.168.4.52:27078/
4. MongoDB server version: 3.6.3
5. ...
6. ...
7. rs1:SECONDARY>         //提示SECONDARY，52为从
8. rs1:SECONDARY>
9. rs1:SECONDARY>
11. [root@192 ~]# mongo --host 192.168.4.53 --port 27079
12. MongoDB shell version v3.6.3
13. connecting to: mongodb://192.168.4.53:27079/
14. MongoDB server version: 3.6.3
15. ...
16. ...
17. rs1:SECONDARY>     //提示SECONDARY，53为从
18. rs1:SECONDARY>

注意：如果初始化错误，重启服务登陆之后重新设置变量，之后再重新初始化

8）查看状态信息

1. rs1:PRIMARY> rs.status()
2. ...
3.     "members" : [
4.         {
5.             "_id" : 0,
6.             "name" : "192.168.4.51:27077",
7.             "health" : 1,
8.             "state" : 1,
9.             "stateStr" : "PRIMARY",
10.             "uptime" : 2295,
11.             ...
12. ...
13.         },
14.         {
15.             "_id" : 1,
16.             "name" : "192.168.4.52:27078",
17.             "health" : 1,
18.             "state" : 2,
19.             "stateStr" : "SECONDARY",
20.             "uptime" : 384,
21.             ...
22. ...
23.         },
24.         {
25.             "_id" : 2,
26.             "name" : "192.168.4.53:27079",
27.             "health" : 1,
28.             "state" : 2,
29.             "stateStr" : "SECONDARY",
30. ...
31. ...

9）查看是否是master库

1. rs1:PRIMARY> rs .isMaster( )
2. {
3.     "hosts" : [
4.         "192.168.4.51:27077",
5.         "192.168.4.52:27078",
6.         "192.168.4.53:27079"
7.     ],
8.     "setName" : "rs1",
9.     "setVersion" : 1,
10.     "ismaster" : true,        //主库
11.     "secondary" : false,
12.     "primary" : "192.168.4.51:27077",
13.     "me" : "192.168.4.51:27077",
14. ...
15. ...

10）验证副本集，同步数据验证（51上面写数据）

1. rs1:PRIMARY> use gamedb2
2. switched to db gamedb2
3. rs1:PRIMARY> db.a.save({name:"yaya",age:75,em:"p@.com"})
4. WriteResult({ "nInserted" : 1 })

52上面查看

1. [root@mongodb52 ~]# mongo --host 192.168.4.52 --port 27078
2. rs1:SECONDARY> db.getMongo().setSlaveOk()
3. rs1:SECONDARY> show dbs        //有gamedb2库
4. admin 0.000GB
5. config 0.000GB
6. ddsdb 0.000GB
7. gamedb2 0.000GB
8. local 0.000GB
9. test 0.000GB

步骤三：切换主库验证

1）自动切换主库验证

关闭51

1. [root@mongodb51 ~]# cmdb        //之前设置的别名
2. killing process with pid: 5656

查看52和53

1. [root@mongodb52 ~]# mongo --host 192.168.4.52 --port 27078
2. MongoDB shell version v3.6.3
3. connecting to: mongodb://192.168.4.52:27078/
4. MongoDB server version: 3.6.3
5. ...
6. ...
7. rs1:PRIMARY>         //52为主
8. rs1:PRIMARY>
10. [root@mongodb53 ~]# mongo --host 192.168.4.53 --port 27079
11. MongoDB shell version v3.6.3
12. connecting to: mongodb://192.168.4.53:27079/
13. MongoDB server version: 3.6.3
14. ...
15. ...
16. rs1:SECONDARY>        //53为从

启动51，启动后不会再变为主，会成为52的从

1. [root@mongodb51 ~]# smdb
2. about to fork child process, waiting until server is ready for connections.
3. forked process: 6598
4. child process started successfully, parent exiting
5. rs1:SECONDARY> rs.isMaster()
6. {
7.     "hosts" : [
8.         "192.168.4.51:27077",
9.         "192.168.4.52:27078",
10.         "192.168.4.53:27079"
11.     ],
12.     "setName" : "rs1",
13.     "setVersion" : 1,
14.     "ismaster" : false,
15.     "secondary" : true,
16.     "primary" : "192.168.4.52:27078",
17.     "me" : "192.168.4.51:27077",
18. ...

2 案例2：文档管理

2.1 问题

• 基于MongoDB环境完成下列练习：
• 插入文档
• 查询文档
• 更新文档
• 删除文档

2.2 步骤

实现此案例需要按照如下步骤进行。

步骤一：管理文档

1）把系统用户信息/etc/passwd存储到mdb库下的user集合里

1. rs1:PRIMARY> use mdb
2. switched to db mdb
3. rs1:PRIMARY> db.user.save({name:"yaya",password:"x",uid:9999,gid:9999,comment:"",homdir:"/home",shell:"/bin/bash"})
4. WriteResult({ "nInserted" : 1 })
5. rs1:PRIMARY> exit
6. bye
8. [root@mongodb52 ~]# mongoexport --host 192.168.4.52 --port 27078 -d mdb -c user -f name,password,uid,gid,comment,homdir,shell --type=csv -o /tmp/user.csv
9. 2018-09-29T11:04:14.967+0800    connected to: 192.168.4.52:27078
10. 2018-09-29T11:04:14.968+0800    exported 1 record
12. [root@mongodb52 ~]# cp /etc/passwd /tmp
13. [root@mongodb52 ~]# sed -i 's/:/,/g' /tmp/passwd
14. [root@mongodb52 ~]# sed -i '$r /tmp/passwd' /tmp/user.csv
15. [root@mongodb52 ~]# mongoimport --host 192.168.4.52 --port 27078 -d mdb -c user --headerline --type=csv /tmp/user.csv
16. 2018-09-29T11:06:08.355+0800    connected to: 192.168.4.52:27078
17. 2018-09-29T11:06:08.363+0800    imported 41 documents

2）查看

1. [root@mongodb52 ~]# mongo --host 192.168.4.52 --port 27078
2. rs1:PRIMARY> use mdb
3. switched to db mdb
4. rs1:PRIMARY> db.user.findOne()
5. {
6.     "_id" : ObjectId("5baeeb37ce3cc5539aa21f38"),
7.     "name" : "yaya",
8.     "password" : "x",
9.     "uid" : 9999,
10.     "gid" : 9999,
11.     "comment" : "",
12.     "homdir" : "/home",
13.     "shell" : "/bin/bash"
14. }

db.user.find（{条件},{定义显示的字段}） #指定查询条件并指定显示的字段

1. rs1:PRIMARY> db.user.find()
2. { "_id" : ObjectId("5baeeb37ce3cc5539aa21f38"), "name" : "yaya", "password" : "x", "uid" : 9999, "gid" : 9999, "comment" : "", "homdir" : "/home", "shell" : "/bin/bash" }
3. ...
4. Type "it" for more            //出现这个按it，默认出现20行

查看每行的name字段

1. rs1:PRIMARY> db.user.find({},{name:1})        
2. { "_id" : ObjectId("5baeeb37ce3cc5539aa21f38"), "name" : "yaya" }
3. ...
4. ...
5. { "_id" : ObjectId("5baeec2001805180a1011843"), "name" : "rpc" }
6. Type "it" for more

不看_id字段

1. rs1:PRIMARY> db.user.find({},{_id:0})
2. { "name" : "yaya", "password" : "x", "uid" : 9999, "gid" : 9999, "comment" : "", "homdir" : "/home", "shell" : "/bin/bash" }
3. ...
4. ...
5. { "name" : "rpc", "password" : "x", "uid" : 32, "gid" : 32, "comment" : "Rpcbind Daemon", "homdir" : "/var/lib/rpcbind", "shell" : "/sbin/nologin" }
6. Type "it" for more

不看_id那一列，看name那一列

1. rs1:PRIMARY> db.user.find({},{_id:0,name:1})
2. { "name" : "yaya" }
3. ...
4. ...
5. { "name" : "rpc" }
6. Type "it" for more

查看以a开头的name字段

1. rs1:PRIMARY> db.user.find({name:/^a/},{_id:0})
2. { "name" : "adm", "password" : "x", "uid" : 3, "gid" : 4, "comment" : "adm", "homdir" : "/var/adm", "shell" : "/sbin/nologin" }
3. { "name" : "abrt", "password" : "x", "uid" : 173, "gid" : 173, "comment" : "", "homdir" : "/etc/abrt", "shell" : "/sbin/nologin" }
4. { "name" : "avahi", "password" : "x", "uid" : 70, "gid" : 70, "comment" : "Avahi mDNS/DNS-SD Stack", "homdir" : "/var/run/avahi-daemon", "shell" : "/sbin/nologin" }

显示查询结果的前一行

limit 数字

1. rs1:PRIMARY> db.user.find({name:/^a/},{_id:0}).limit (1)
2. { "name" : "adm", "password" : "x", "uid" : 3, "gid" : 4, "comment" : "adm", "homdir" : "/var/adm", "shell" : "/sbin/nologin" }

显示name字段以a开头的第一行

1. rs1:PRIMARY> db.user.findOne({name:/^a/},{_id:0,name:1,shell:1,uid:1})
2. { "name" : "adm", "uid" : 3, "shell" : "/sbin/nologin" }

跳过几行显示 （2行）

skip 数字

1. rs1:PRIMARY> db.user.find({name:/^a/},{_id:0,name:1,shell:1}).skip (2)
2. { "name" : "avahi", "shell" : "/sbin/nologin" }

默认升序排序

sort 字段名

1. rs1:PRIMARY> db.user.find({name:/^a/},{_id:0,name:1,shell:1,uid:1}).sort({uid:1})
2. { "name" : "adm", "uid" : 3, "shell" : "/sbin/nologin" }
3. { "name" : "avahi", "uid" : 70, "shell" : "/sbin/nologin" }
4. { "name" : "abrt", "uid" : 173, "shell" : "/sbin/nologin" }

降序排序

1. rs1:PRIMARY> db.user.find({name:/^a/},{_id:0,name:1,shell:1,uid:1}).sort({uid:-1})
2. { "name" : "abrt", "uid" : 173, "shell" : "/sbin/nologin" }
3. { "name" : "avahi", "uid" : 70, "shell" : "/sbin/nologin" }
4. { "name" : "adm", "uid" : 3, "shell" : "/sbin/nologin" }

显示name字段以a开头和uid为3的所有行

1. rs1:PRIMARY> db.user.find({name:/^a/,uid:3},{_id:0,name:1,shell:1,uid:1})
2. { "name" : "adm", "uid" : 3, "shell" : "/sbin/nologin" }

3）条件判断的表示方式

$in 在...里

1. rs1:PRIMARY> db.user.find({uid:{$in:[1,6,9]}})        //uid的为1或者6或者9的匹配
2. { "_id" : ObjectId("5baeec2001805180a1011833"), "name" : "bin", "password" : "x", "uid" : 1, "gid" : 1, "comment" : "bin", "homdir" : "/bin", "shell" : "/sbin/nologin" }
3. { "_id" : ObjectId("5baeec2001805180a1011838"), "name" : "shutdown", "password" : "x", "uid" : 6, "gid" : 0, "comment" : "shutdown", "homdir" : "/sbin", "shell" : "/sbin/shutdown" }

$nin 不在...里

1. rs1:PRIMARY> db.user.find({uid:{$nin:[1,6,9]}},{_id:0,name:1,uid:1})
2. { "name" : "yaya", "uid" : 9999 }
3. ...
4. ...
5. { "name" : "saslauth", "uid" : 996 }
6. Type "it" for more

$or 条件满足任意其中一个即可

1. rs1:PRIMARY> db.user.find({$or:[{name:"root"},{uid:1}]},{_id:0,name:1,uid:1})
2. { "name" : "root", "uid" : 0 }
3. { "name" : "bin", "uid" : 1 }

4）正则匹配，以a开头的name字段

1. rs1:PRIMARY> db.user.find({name:/^a/},{_id:0,name:1,uid:1})
2. { "name" : "adm", "uid" : 3 }
3. { "name" : "abrt", "uid" : 173 }
4. { "name" : "avahi", "uid" : 70 }

5）数值比较

$lt(小于) $lte（小于等于） $gt（大于） $gte（大于等于） $ne（不等于）

1. rs1:PRIMARY> db.user.find({uid:{$gte:10,$lte:40}},{_id:0,name:1,uid:1})
2. { "name" : "operator", "uid" : 11 }
3. { "name" : "games", "uid" : 12 }
4. { "name" : "ftp", "uid" : 14 }
5. { "name" : "rpc", "uid" : 32 }
6. { "name" : "rpcuser", "uid" : 29 }
7. { "name" : "ntp", "uid" : 38 }

匹配null：可以匹配没有的字段，也可以检查这个字段有没有

1. rs1:PRIMARY> db.user.save({name:null,uid:null})
2. WriteResult({ "nInserted" : 1 })
3. rs1:PRIMARY> db.user.find({name:null})
4. { "_id" : ObjectId("5baef385f9f3bf625ea1dbd6"), "name" : null, "uid" : null }
6. rs1:PRIMARY> db.user.find({shell:null})    //表示此条文档没有shell字段
7. { "_id" : ObjectId("5baef385f9f3bf625ea1dbd6"), "name" : null, "uid" : null }
8. rs1:PRIMARY>

6）save和insert的区别

相同点：当集合不存在时创建集合，并插入记录

不同点：save() _id字段值已经存在时，修改文档字段值

insert() _id字段值已经存在时，放弃修改文档字段值

1. rs1:PRIMARY> db.t1.save({name:"bob",age:19})
2. WriteResult({ "nInserted" : 1 })
3. rs1:PRIMARY> db.t1.insert({name:"bob",age:19})
4. WriteResult({ "nInserted" : 1 })
6. rs1:PRIMARY> db.t1.save({_id:7,name:"bob",age:19})
7. WriteResult({ "nMatched" : 0, "nUpserted" : 1, "nModified" : 0, "_id" : 7 })
8. rs1:PRIMARY> db.t1.find()
9. ...
10. ...
11. { "_id" : 7, "name" : "bob", "age" : 19 }
12. rs1:PRIMARY> db.t1.save({_id:7,name:"tom",age:19})        //把上一条的记录直接修改
13. WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })
14. rs1:PRIMARY> db.t1.find()
15. ...
16. ...
17. { "_id" : 7, "name" : "tom", "age" : 19 }
18. rs1:PRIMARY>
21. rs1:PRIMARY>
22. rs1:PRIMARY> db.t1.insert({_id:8,name:"tom",age:19})        //可以存上
23. WriteResult({ "nInserted" : 1 })
24. rs1:PRIMARY> db.t1.insert({_id:8,name:"tom",age:19})        //存不上
25. WriteResult({
26.     "nInserted" : 0,
27.     "writeError" : {
28.         "code" : 11000,
29.         "errmsg" : "E11000 duplicate key error collection: mdb.t1 index: _id_ dup key: { : 8.0 }"
30.     }
31. })

7）插入多行文档

1. rs1:PRIMARY> db.t1.insertMany([{name:"xiaojiu"},{name:"laoshi"}])
2. {
3.     "acknowledged" : true,
4.     "insertedIds" : [
5.         ObjectId("5baef526f9f3bf625ea1dbd9"),
6.         ObjectId("5baef526f9f3bf625ea1dbda")
7.     ]
8. }
10. rs1:PRIMARY> db.t1.find()
11. ...
12. ...
13. { "_id" : ObjectId("5baef526f9f3bf625ea1dbd9"), "name" : "xiaojiu" }
14. { "_id" : ObjectId("5baef526f9f3bf625ea1dbda"), "name" : "laoshi" }

8）update修改

1. rs1:PRIMARY> db.user.update({name:"root"},{password:"XXX"})
2. //如果这一列不写完整，这一行除了password这一行，这一列的其他值都没有了相当于删除（要写完整）
3. WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })
4. rs1:PRIMARY> db.t1.find({name:"root"})
5. rs1:PRIMARY> db.user.find({name:"root"}) //没有东西，除了password:"XXX"

9）$set 条件匹配时，修改指定字段的值(局部修改)

1. rs1:PRIMARY> db.user.update({name:"adm"},{$set:{password:"AAA"}})
2. WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })
3. rs1:PRIMARY> db.user.find({name:"adm"})        //还存在
4. { "_id" : ObjectId("5baeec2001805180a1011835"), "name" : "adm", "password" : "AAA", "uid" : 3, "gid" : 4, "comment" : "adm", "homdir" : "/var/adm", "shell" : "/sbin/nologin" }
7. rs1:PRIMARY> db.user.update({name:/^r/},{$set:{password:"FFF"}})        
8. //默认修改匹配条件的第一行
9. WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })    
10. rs1:PRIMARY> db.user.update({name:/^a/},{$set:{password:"FFF"}},false,true)
11. //改匹配到的所有
12. WriteResult({ "nMatched" : 3, "nUpserted" : 0, "nModified" : 3 })

10）$unset 删除与条件匹配文档的字段

1. rs1:PRIMARY> db.user.update({name:"sync"},{$unset:{password:1}})     
2. //删除password字段
3. WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })

11）数组

1. rs1:PRIMARY> db.user.insert({name:"bob",like:["a","b","c","d","e","f",]})
2. WriteResult({ "nInserted" : 1 })

$pop 删除数组末尾一个元素，1删除最后一个，-1删除第一个

1. rs1:PRIMARY> db.user.update({name:"bob"},{$pop:{like:1}})    
2. //删除匹配的第一条的最后一个
3. WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })
4. rs1:PRIMARY> db.user.update({name:"bob"},{$pop:{like:-1}})    
5. //删除匹配的第一条的第一个
6. WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })

$push 向数组中添加新元素

1. rs1:PRIMARY> db.user.update({name:"bob"},{$push:{like:"Z"}})        //默认添加到最后
2. WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })
3. rs1:PRIMARY> db.user.update({name:"bob"},{$push:{like:"W"}})
4. WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })
5. rs1:PRIMARY> db.user.find({name:"bob"})
6. { "_id" : ObjectId("5baef7b2034891a205de2959"), "name" : "bob", "like" : [ "b", "c", "d", "e", "Z", "W" ] }

$addToSet 避免重复添加

1. rs1:PRIMARY> db.user.update({name:"bob"},{$addToSet:{like:"W"}})
2. WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 0 })
3. rs1:PRIMARY> db.user.find({name:"bob"})
4. { "_id" : ObjectId("5baef7b2034891a205de2959"), "name" : "bob", "like" : [ "b", "c", "d", "e", "Z", "W" ] }

$pull 删除数组里的指定元素，若有两个bob可以用_id值定义把name:"bob"换成id值

1. rs1:PRIMARY> db.user.update({name:"bob"},{$pull:{like:"c"}})
2. WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })
3. rs1:PRIMARY> db.user.find({name:"bob"})
4. { "_id" : ObjectId("5baef7b2034891a205de2959"), "name" : "bob", "like" : [ "b", "d", "e", "Z", "W" ] }
5. rs1:PRIMARY> db.user.update({"_id":ObjectId("5afc1a717eff45e9cfc57ed3")},{$push:{like:"S"}})
6. WriteResult({ "nMatched" : 0, "nUpserted" : 0, "nModified" : 0 })
7. rs1:PRIMARY>

$inc 条件匹配时，字段值自加或自减

1. rs1:PRIMARY> db.user.update({uid:{$lte:10}},{$inc:{uid:2}})         
2. //设置字段值自加2,默认改第一行
3. WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })
5. rs1:PRIMARY> db.user.update({uid:{$lte:10}},{$inc:{uid:2}},false,true)    
6. //设置字段值自加2，false,true改全部
7. WriteResult({ "nMatched" : 8, "nUpserted" : 0, "nModified" : 8 })
8. rs1:PRIMARY>
10. rs1:PRIMARY> db.user.update({uid:{$lte:10}},{$inc:{uid:-1}})
11. //负数时是自减1，默认改第一行
12. WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })

12）删除文档

remove()与drop()的区别

remove()删除文档时不删除索引

drop()删除集合的时候同时删除索引

1. rs1:PRIMARY> db.t1.remove({})
2. WriteResult({ "nRemoved" : 6 })
4. rs1:PRIMARY> db.user.remove({name:"/^a/"})        //删除以a开头的记录
5. WriteResult({ "nRemoved" : 0 })
7. rs1:PRIMARY> db.t1.drop()        //删除集合t1
8. true
9. rs1:PRIMARY>