MongoDB基本管理命令

MongoDB是一个NoSQL数据库系统：一个数据库可以包含多个集合（Collection），每个集合对应于关系数据库中的表；而每个集合中可以存储一组由列标识的记录，列是可以自由定义的，非常灵活，由一组列标识的实体的集合对应于关系数据库表中的行。下面通过熟悉MongoDB的基本管理命令，来了解MongoDB提供的DBMS的基本功能和行为。

MongoDB命令帮助系统

在安装MongoDB后，启动服务器进程（mongod），可以通过在客户端命令mongo实现对MongoDB的管理和监控。看一下MongoDB的命令帮助系统：

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1. root@dev2:~# mongo
2. MongoDB shell version: 1.8.3
3. connecting to: test
4. > help
5. db.help() help on db methods
6. db.mycoll.help() help on collection methods
7. rs.help() help on replica set methods
8. help connect connecting to a db help
9. help admin administrative help
10. help misc misc things to know
11. help mr mapreduce help
12. show dbs show database names
13. show collections show collections in current database
14. show users show users in current database
15. show profile show most recent system.profile entries with time >= 1ms
16. use set current database
17. db.foo.find() list objects in collection foo
18. db.foo.find( { a : 1 } ) list objects in foo where a == 1
19. it result of the last line evaluated; use to further iterate
20. DBQuery.shellBatchSize = x set default number of items to display on shell
21. exit quit the mongo shell

root@dev2:~# mongo
MongoDB shell version: 1.8.3
connecting to: test
> help
        db.help()                    help on db methods
        db.mycoll.help()             help on collection methods
        rs.help()                    help on replica set methods
        help connect                 connecting to a db help
        help admin                   administrative help
        help misc                    misc things to know
        help mr                      mapreduce help

        show dbs                     show database names
        show collections             show collections in current database
        show users                   show users in current database
        show profile                 show most recent system.profile entries with time >= 1ms
        use                 set current database
        db.foo.find()                list objects in collection foo
        db.foo.find( { a : 1 } )     list objects in foo where a == 1
        it                           result of the last line evaluated; use to further iterate
        DBQuery.shellBatchSize = x   set default number of items to display on shell
        exit                         quit the mongo shell

这是MongoDB最顶层的命令列表，主要告诉我们管理数据库相关的一些抽象的范畴：数据库操作帮助、集合操作帮助、管理帮助。如果你想了解数据库操作更详细的帮助命令，可以直接使用db.help()，如下所示：

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1. > db.help()
2. DB methods:
3. db.addUser(username, password[, readOnly=false])
4. db.auth(username, password)
5. db.cloneDatabase(fromhost)
6. db.commandHelp(name) returns the help for the command
7. db.copyDatabase(fromdb, todb, fromhost)
8. db.createCollection(name, { size : ..., capped : ..., max : ... } )
9. db.currentOp() displays the current operation in the db
10. db.dropDatabase()
11. db.eval_r(func, args) run code server-side
12. db.getCollection(cname) same as db['cname'] or db.cname
13. db.getCollectionNames()
14. db.getLastError() - just returns the err msg string
15. db.getLastErrorObj() - return full status object
16. db.getMongo() get the server connection object
17. db.getMongo().setSlaveOk() allow this connection to read from the nonmaster member of a replica pair
18. db.getName()
19. db.getPrevError()
20. db.getProfilingLevel() - deprecated
21. db.getProfilingStatus() - returns if profiling is on and slow threshold
22. db.getReplicationInfo()
23. db.getSiblingDB(name) get the db at the same server as this one
24. db.isMaster() check replica primary status
25. db.killOp(opid) kills the current operation in the db
26. db.listCommands() lists all the db commands
27. db.printCollectionStats()
28. db.printReplicationInfo()
29. db.printSlaveReplicationInfo()
30. db.printShardingStatus()
31. db.removeUser(username)
32. db.repairDatabase()
33. db.resetError()
34. db.runCommand(cmdObj) run a database command. if cmdObj is a string, turns it into { cmdObj : 1 }
35. db.serverStatus()
36. db.setProfilingLevel(level,) 0=off 1=slow 2=all
37. db.shutdownServer()
38. db.stats()
39. db.version() current version of the server
40. db.getMongo().setSlaveOk() allow queries on a replication slave server

> db.help()
DB methods:
        db.addUser(username, password[, readOnly=false])
        db.auth(username, password)
        db.cloneDatabase(fromhost)
        db.commandHelp(name) returns the help for the command
        db.copyDatabase(fromdb, todb, fromhost)
        db.createCollection(name, { size : ..., capped : ..., max : ... } )
        db.currentOp() displays the current operation in the db
        db.dropDatabase()
        db.eval_r(func, args) run code server-side
        db.getCollection(cname) same as db['cname'] or db.cname
        db.getCollectionNames()
        db.getLastError() - just returns the err msg string
        db.getLastErrorObj() - return full status object
        db.getMongo() get the server connection object
        db.getMongo().setSlaveOk() allow this connection to read from the nonmaster member of a replica pair
        db.getName()
        db.getPrevError()
        db.getProfilingLevel() - deprecated
        db.getProfilingStatus() - returns if profiling is on and slow threshold 
        db.getReplicationInfo()
        db.getSiblingDB(name) get the db at the same server as this one
        db.isMaster() check replica primary status
        db.killOp(opid) kills the current operation in the db
        db.listCommands() lists all the db commands
        db.printCollectionStats()
        db.printReplicationInfo()
        db.printSlaveReplicationInfo()
        db.printShardingStatus()
        db.removeUser(username)
        db.repairDatabase()
        db.resetError()
        db.runCommand(cmdObj) run a database command.  if cmdObj is a string, turns it into { cmdObj : 1 }
        db.serverStatus()
        db.setProfilingLevel(level,) 0=off 1=slow 2=all
        db.shutdownServer()
        db.stats()
        db.version() current version of the server
        db.getMongo().setSlaveOk() allow queries on a replication slave server

对数据库进行管理和操作的基本命令，可以从上面获取到。如果想要得到更多，而且每个命令的详细用法，可以使用上面列出的db.listCommands()查询。

另一个比较基础的是对指定数据库的集合进行操作、管理和监控，可以通过查询db.mycoll.help()获取到：

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1. > db.mycoll.help()
2. DBCollection help
3. db.mycoll.find().help() - show DBCursor help
4. db.mycoll.count()
5. db.mycoll.dataSize()
6. db.mycoll.distinct( key ) - eg. db.mycoll.distinct( 'x' )
7. db.mycoll.drop() drop the collection
8. db.mycoll.dropIndex(name)
9. db.mycoll.dropIndexes()
10. db.mycoll.ensureIndex(keypattern[,options]) - options is an object with these possible fields: name, unique, dropDups
11. db.mycoll.reIndex()
12. db.mycoll.find([query],[fields]) - query is an optional query filter. fields is optional set of fields to return.
13. e.g. db.mycoll.find( {x:77} , {name:1, x:1} )
14. db.mycoll.find(...).count()
15. db.mycoll.find(...).limit(n)
16. db.mycoll.find(...).skip(n)
17. db.mycoll.find(...).sort(...)
18. db.mycoll.findOne([query])
19. db.mycoll.findAndModify( { update : ... , remove : bool [, query: {}, sort: {}, 'new': false] } )
20. db.mycoll.getDB() get DB object associated with collection
21. db.mycoll.getIndexes()
22. db.mycoll.group( { key : ..., initial: ..., reduce : ...[, cond: ...] } )
23. db.mycoll.mapReduce( mapFunction , reduceFunction , )
24. db.mycoll.remove(query)
25. db.mycoll.renameCollection( newName , ) renames the collection.
26. db.mycoll.runCommand( name , ) runs a db command with the given name where the first param is the collection name
27. db.mycoll.save(obj)
28. db.mycoll.stats()
29. db.mycoll.storageSize() - includes free space allocated to this collection
30. db.mycoll.totalIndexSize() - size in bytes of all the indexes
31. db.mycoll.totalSize() - storage allocated for all data and indexes
32. db.mycoll.update(query, object[, upsert_bool, multi_bool])
33. db.mycoll.validate() - SLOW
34. db.mycoll.getShardVersion() - only for use with sharding

> db.mycoll.help()
DBCollection help
        db.mycoll.find().help() - show DBCursor help
        db.mycoll.count()
        db.mycoll.dataSize()
        db.mycoll.distinct( key ) - eg. db.mycoll.distinct( 'x' )
        db.mycoll.drop() drop the collection
        db.mycoll.dropIndex(name)
        db.mycoll.dropIndexes()
        db.mycoll.ensureIndex(keypattern[,options]) - options is an object with these possible fields: name, unique, dropDups
        db.mycoll.reIndex()
        db.mycoll.find([query],[fields]) - query is an optional query filter. fields is optional set of fields to return.
                                                      e.g. db.mycoll.find( {x:77} , {name:1, x:1} )
        db.mycoll.find(...).count()
        db.mycoll.find(...).limit(n)
        db.mycoll.find(...).skip(n)
        db.mycoll.find(...).sort(...)
        db.mycoll.findOne([query])
        db.mycoll.findAndModify( { update : ... , remove : bool [, query: {}, sort: {}, 'new': false] } )
        db.mycoll.getDB() get DB object associated with collection
        db.mycoll.getIndexes()
        db.mycoll.group( { key : ..., initial: ..., reduce : ...[, cond: ...] } )
        db.mycoll.mapReduce( mapFunction , reduceFunction ,  )
        db.mycoll.remove(query)
        db.mycoll.renameCollection( newName ,  ) renames the collection.
        db.mycoll.runCommand( name ,  ) runs a db command with the given name where the first param is the collection name
        db.mycoll.save(obj)
        db.mycoll.stats()
        db.mycoll.storageSize() - includes free space allocated to this collection
        db.mycoll.totalIndexSize() - size in bytes of all the indexes
        db.mycoll.totalSize() - storage allocated for all data and indexes
        db.mycoll.update(query, object[, upsert_bool, multi_bool])
        db.mycoll.validate() - SLOW
        db.mycoll.getShardVersion() - only for use with sharding

有关数据库和集合管理的相关命令，是最基础和最常用的，如集合查询、索引操作等。

基本命令及实例

下面通过实际的例子来演示一些常见的命令：

（一）基本命令

1、show dbs

显示当前数据库服务器上的数据库

2、use pagedb

切换到指定数据库pagedb的上下文，可以在此上下文中管理pagedb数据库以及其中的集合等

3、show collections

显示数据库中所有的集合（collection）

4、db.serverStatus()

查看数据库服务器的状态。示例如下所示：

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1. {
2. "host" : "dev2",
3. "version" : "1.8.3",
4. "process" : "mongod",
5. "uptime" : 845446,
6. "uptimeEstimate" : 839192,
7. "localTime" : ISODate("2011-12-27T04:03:12.512Z"),
8. "globalLock" : {
9. "totalTime" : 845445636925,
10. "lockTime" : 13630973982,
11. "ratio" : 0.016122827283818857,
12. "currentQueue" : {
13. "total" : 0,
14. "readers" : 0,
15. "writers" : 0
16. },
17. "activeClients" : {
18. "total" : 0,
19. "readers" : 0,
20. "writers" : 0
21. }
22. },
23. "mem" : {
24. "bits" : 64,
25. "resident" : 12208,
26. "virtual" : 466785,
27. "supported" : true,
28. "mapped" : 466139
29. },
30. "connections" : {
31. "current" : 27,
32. "available" : 792
33. },
34. "extra_info" : {
35. "note" : "fields vary by platform",
36. "heap_usage_bytes" : 70895216,
37. "page_faults" : 17213898
38. },
39. "indexCounters" : {
40. "btree" : {
41. "accesses" : 4466653,
42. "hits" : 4465526,
43. "misses" : 1127,
44. "resets" : 0,
45. "missRatio" : 0.00025231420484197006
46. }
47. },
48. "backgroundFlushing" : {
49. "flushes" : 14090,
50. "total_ms" : 15204393,
51. "average_ms" : 1079.0910574875797,
52. "last_ms" : 669,
53. "last_finished" : ISODate("2011-12-27T04:02:28.713Z")
54. },
55. "cursors" : {
56. "totalOpen" : 3,
57. "clientCursors_size" : 3,
58. "timedOut" : 53
59. },
60. "network" : {
61. "bytesIn" : 63460818650,
62. "bytesOut" : 763926196104,
63. "numRequests" : 67055921
64. },
65. "opcounters" : {
66. "insert" : 7947057,
67. "query" : 35720451,
68. "update" : 16263239,
69. "delete" : 154,
70. "getmore" : 91707,
71. "command" : 68520
72. },
73. "asserts" : {
74. "regular" : 0,
75. "warning" : 1,
76. "msg" : 0,
77. "user" : 7063866,
78. "rollovers" : 0
79. },
80. "writeBacksQueued" : false,
81. "ok" : 1
82. }

{
        "host" : "dev2",
        "version" : "1.8.3",
        "process" : "mongod",
        "uptime" : 845446,
        "uptimeEstimate" : 839192,
        "localTime" : ISODate("2011-12-27T04:03:12.512Z"),
        "globalLock" : {
                "totalTime" : 845445636925,
                "lockTime" : 13630973982,
                "ratio" : 0.016122827283818857,
                "currentQueue" : {
                        "total" : 0,
                        "readers" : 0,
                        "writers" : 0
                },
                "activeClients" : {
                        "total" : 0,
                        "readers" : 0,
                        "writers" : 0
                }
        },
        "mem" : {
                "bits" : 64,
                "resident" : 12208,
                "virtual" : 466785,
                "supported" : true,
                "mapped" : 466139
        },
        "connections" : {
                "current" : 27,
                "available" : 792
        },
        "extra_info" : {
                "note" : "fields vary by platform",
                "heap_usage_bytes" : 70895216,
                "page_faults" : 17213898
        },
        "indexCounters" : {
                "btree" : {
                        "accesses" : 4466653,
                        "hits" : 4465526,
                        "misses" : 1127,
                        "resets" : 0,
                        "missRatio" : 0.00025231420484197006
                }
        },
        "backgroundFlushing" : {
                "flushes" : 14090,
                "total_ms" : 15204393,
                "average_ms" : 1079.0910574875797,
                "last_ms" : 669,
                "last_finished" : ISODate("2011-12-27T04:02:28.713Z")
        },
        "cursors" : {
                "totalOpen" : 3,
                "clientCursors_size" : 3,
                "timedOut" : 53
        },
        "network" : {
                "bytesIn" : 63460818650,
                "bytesOut" : 763926196104,
                "numRequests" : 67055921
        },
        "opcounters" : {
                "insert" : 7947057,
                "query" : 35720451,
                "update" : 16263239,
                "delete" : 154,
                "getmore" : 91707,
                "command" : 68520
        },
        "asserts" : {
                "regular" : 0,
                "warning" : 1,
                "msg" : 0,
                "user" : 7063866,
                "rollovers" : 0
        },
        "writeBacksQueued" : false,
        "ok" : 1
}

有时，通过查看数据库服务器的状态，可以判断数据库是否存在问题，如果有问题，如数据损坏，可以及时执行修复。

5、查询指定数据库统计信息

use fragment

db.stats()

查询结果示例如下所示：

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1. > db.stats()
2. {
3. "db" : "fragment",
4. "collections" : 12,
5. "objects" : 384553,
6. "avgObjSize" : 3028.40198360174,
7. "dataSize" : 1164581068,
8. "storageSize" : 1328351744,
9. "numExtents" : 109,
10. "indexes" : 10,
11. "indexSize" : 16072704,
12. "fileSize" : 4226809856,
13. "ok" : 1
14. }

> db.stats()
{
        "db" : "fragment",
        "collections" : 12,
        "objects" : 384553,
        "avgObjSize" : 3028.40198360174,
        "dataSize" : 1164581068,
        "storageSize" : 1328351744,
        "numExtents" : 109,
        "indexes" : 10,
        "indexSize" : 16072704,
        "fileSize" : 4226809856,
        "ok" : 1
}

显示fragment数据库的统计信息。

6、查询指定数据库包含的集合名称列表

db.getCollectionNames()

结果如下所示：

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1. > db.getCollectionNames()
2. [
3. "17u",
4. "baseSe",
5. "bytravel",
6. "daodao",
7. "go2eu",
8. "lotour",
9. "lvping",
10. "mafengwo",
11. "sina",
12. "sohu",
13. "system.indexes"
14. ]

> db.getCollectionNames()
[
        "17u",
        "baseSe",
        "bytravel",
        "daodao",
        "go2eu",
        "lotour",
        "lvping",
        "mafengwo",
        "sina",
        "sohu",
        "system.indexes"
]

（二）基本DDL和DML

1、创建数据库

如果你习惯了关系型数据库，你可能会寻找相关的创建数据库的命令。在MongoDB中，你可以直接通过use dbname来切换到这个数据库上下文下面，系统会自动延迟创建该数据库，例如：

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1. > show dbs
2. admin 0.03125GB
3. local (empty)
4. pagedb 0.03125GB
5. test 0.03125GB
6. > use LuceneIndexDB
7. switched to db LuceneIndexDB
8. > show dbs
9. admin 0.03125GB
10. local (empty)
11. pagedb 0.03125GB
12. test 0.03125GB
13. > db
14. LuceneIndexDB
15. > db.storeCollection.save({'version':'3.5', 'segment':'e3ol6'})
16. > show dbs
17. LuceneIndexDB 0.03125GB
18. admin 0.03125GB
19. local (empty)
20. pagedb 0.03125GB
21. test 0.03125GB
22. >

> show dbs
admin   0.03125GB
local   (empty)
pagedb  0.03125GB
test    0.03125GB
> use LuceneIndexDB
switched to db LuceneIndexDB
> show dbs
admin   0.03125GB
local   (empty)
pagedb  0.03125GB
test    0.03125GB
> db
LuceneIndexDB
> db.storeCollection.save({'version':'3.5', 'segment':'e3ol6'})
> show dbs
LuceneIndexDB   0.03125GB
admin   0.03125GB
local   (empty)
pagedb  0.03125GB
test    0.03125GB
>

可见，在use指定数据库后，并且向指定其中的一个集合并插入数据后，数据库和集合都被创建了。

2、删除数据库

直接使用db.dropDatabase()即可删除数据库。

3、创建集合

可以使用命令db.createCollection(name, { size : ..., capped : ..., max : ... } )创建集合，示例如下所示：

[plain] view plain copy print ?

1. > db.createCollection('replicationColletion', {'capped':true, 'size':10240, 'max':17855200})
2. { "ok" : 1 }
3. > show collections
4. replicationColletion
5. storeCollection
6. system.indexes

> db.createCollection('replicationColletion', {'capped':true, 'size':10240, 'max':17855200})
{ "ok" : 1 }
> show collections
replicationColletion
storeCollection
system.indexes

4、删除集合

删除集合，可以执行db.mycoll.drop()。

5、插入更新记录

直接使用集合的save方法，如下所示：

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1. > db.storeCollection.save({'version':'3.5', 'segment':'e3ol6'})

> db.storeCollection.save({'version':'3.5', 'segment':'e3ol6'})

更新记录，使用save会将原来的记录值进行覆盖实现记录更新。

6、查询一条记录

使用findOne()函数，参数为查询条件，可选，系统会随机查询获取到满足条件的一条记录（如果存在查询结果数量大于等于1）示例如下所示：

[plain] view plain copy print ?

1. > db.storeCollection.findOne({'version':'3.5'})
2. {
3. "_id" : ObjectId("4ef970f23c1fc4613425accc"),
4. "version" : "3.5",
5. "segment" : "e3ol6"
6. }

> db.storeCollection.findOne({'version':'3.5'})
{
        "_id" : ObjectId("4ef970f23c1fc4613425accc"),
        "version" : "3.5",
        "segment" : "e3ol6"
}

7、查询多条记录

使用find()函数，参数指定查询条件，不指定条件则查询全部记录。

8、删除记录

使用集合的remove()方法，参数指定为查询条件，示例如下所示：

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1. > db.storeCollection.remove({'version':'3.5'})
2. > db.storeCollection.findOne()
3. null

> db.storeCollection.remove({'version':'3.5'})
> db.storeCollection.findOne()
null

9、创建索引

可以使用集合的ensureIndex(keypattern[,options])方法，示例如下所示：

[plain] view plain copy print ?

1. > use pagedb
2. switched to db pagedb
3. > db.page.ensureIndex({'title':1, 'url':-1})
4. > db.system.indexes.find()
5. { "name" : "_id_", "ns" : "pagedb.page", "key" : { "_id" : 1 }, "v" : 0 }
6. { "name" : "_id_", "ns" : "pagedb.system.users", "key" : { "_id" : 1 }, "v" : 0}
7. { "_id" : ObjectId("4ef977633c1fc4613425accd"), "ns" : "pagedb.page", "key" : {"title" : 1, "url" : -1 }, "name" : "title_1_url_-1", "v" : 0 }

> use pagedb
switched to db pagedb
> db.page.ensureIndex({'title':1, 'url':-1})
> db.system.indexes.find()
{ "name" : "_id_", "ns" : "pagedb.page", "key" : { "_id" : 1 }, "v" : 0 }
{ "name" : "_id_", "ns" : "pagedb.system.users", "key" : { "_id" : 1 }, "v" : 0}
{ "_id" : ObjectId("4ef977633c1fc4613425accd"), "ns" : "pagedb.page", "key" : {"title" : 1, "url" : -1 }, "name" : "title_1_url_-1", "v" : 0 }

上述，ensureIndex方法参数中，数字1表示升序，-1表示降序。

使用db.system.indexes.find()可以查询全部索引。

10、查询索引

我们为集合建立的索引，那么可以通过集合的getIndexes()方法实现查询，示例如下所示：

[plain] view plain copy print ?

1. > db.page.getIndexes()
2. [
3. {
4. "name" : "_id_",
5. "ns" : "pagedb.page",
6. "key" : {
7. "_id" : 1
8. },
9. "v" : 0
10. },
11. {
12. "_id" : ObjectId("4ef977633c1fc4613425accd"),
13. "ns" : "pagedb.page",
14. "key" : {
15. "title" : 1,
16. "url" : -1
17. },
18. "name" : "title_1_url_-1",
19. "v" : 0
20. }
21. ]

> db.page.getIndexes()
[
        {
                "name" : "_id_",
                "ns" : "pagedb.page",
                "key" : {
                        "_id" : 1
                },
                "v" : 0
        },
        {
                "_id" : ObjectId("4ef977633c1fc4613425accd"),
                "ns" : "pagedb.page",
                "key" : {
                        "title" : 1,
                        "url" : -1
                },
                "name" : "title_1_url_-1",
                "v" : 0
        }
]

当然，如果需要查询系统中全部的索引，可以使用db.system.indexes.find()函数。
11、删除索引

删除索引给出了两个方法：

[plain] view plain copy print ?

1. db.mycoll.dropIndex(name)
2. db.mycoll.dropIndexes()

        db.mycoll.dropIndex(name)
        db.mycoll.dropIndexes()

第一个通过指定索引名称，第二个删除指定集合的全部索引。

12、索引重建

可以通过集合的reIndex()方法进行索引的重建，示例如下所示：

[plain] view plain copy print ?

1. > db.page.reIndex()
2. {
3. "nIndexesWas" : 2,
4. "msg" : "indexes dropped for collection",
5. "ok" : 1,
6. "nIndexes" : 2,
7. "indexes" : [
8. {
9. "name" : "_id_",
10. "ns" : "pagedb.page",
11. "key" : {
12. "_id" : 1
13. },
14. "v" : 0
15. },
16. {
17. "_id" : ObjectId("4ef977633c1fc4613425accd"),
18. "ns" : "pagedb.page",
19. "key" : {
20. "title" : 1,
21. "url" : -1
22. },
23. "name" : "title_1_url_-1",
24. "v" : 0
25. }
26. ],
27. "ok" : 1
28. }

> db.page.reIndex()
{
        "nIndexesWas" : 2,
        "msg" : "indexes dropped for collection",
        "ok" : 1,
        "nIndexes" : 2,
        "indexes" : [
                {
                        "name" : "_id_",
                        "ns" : "pagedb.page",
                        "key" : {
                                "_id" : 1
                        },
                        "v" : 0
                },
                {
                        "_id" : ObjectId("4ef977633c1fc4613425accd"),
                        "ns" : "pagedb.page",
                        "key" : {
                                "title" : 1,
                                "url" : -1
                        },
                        "name" : "title_1_url_-1",
                        "v" : 0
                }
        ],
        "ok" : 1
}

13、统计集合记录数

use fragment

db.baseSe.count()
统计结果，如下所示：

[plain] view plain copy print ?

1. > use fragment
2. switched to db fragment
3. > db.baseSe.count()
4. 36749

> use fragment
switched to db fragment
> db.baseSe.count()
36749

上述统计了数据库fragment的baseSe集合中记录数。
14、查询并统计结果记录数

use fragment
db.baseSe.find().count()

find()可以提供查询参数，然后查询并统计结果，如下所示：

[plain] view plain copy print ?

1. > use fragment
2. switched to db fragment
3. > db.baseSe.find().count()
4. 36749

> use fragment
switched to db fragment
> db.baseSe.find().count()
36749

上述执行先根据查询条件查询结果，然后统计了查询数据库fragment的baseSe结果记录集合中记录数。

15、查询指定数据库的集合当前可用的存储空间

use fragment
> db.baseSe.storageSize()
142564096

16、查询指定数据库的集合分配的存储空间

> db.baseSe.totalSize()

144096000

上述查询结果中，包括为集合（数据及其索引存储）分配的存储空间。

（三）启动与终止

1、正常启动

mongod --dbpath /usr/mongo/data --logfile /var/mongo.log

说明：

指定数据存储目录和日志目录，如果采用安全认证模式，需要加上--auth选项，如：

mongod --auth --dbpath /usr/mongo/data --logfile /var/mongo.log

2、以修复模式启动

mongod --repair

以修复模式启动数据库。

实际很可能数据库数据损坏或数据状态不一致，导致无法正常启动MongoDB服务器，根据启动信息可以看到需要进行修复。或者执行：

mongod -f /etc/mongodb.conf --repair

3、终止服务器进程

db.shutdownServer()

终止数据库服务器进程。或者，可以直接kill掉mongod进程即可。

（四）安全管理

1、以安全认证模式启动

mongod --auth --dbpath /usr/mongo/data --logfile /var/mongo.log

使用--auth选项启动mongod进程即可启用认证模式。
或者，也可以修改/etc/mongodb.conf，设置auth=true，重启mongod进程。

2、添加用户

db.addUser("admin", ",�3_kj~00Opoo0+\/")

添加数据库用户，添加成功，则显示结果如下所示：

[plain] view plain copy print ?

1. {
2. "user" : "admin",
3. "readOnly" : false,
4. "pwd" : "995d2143e0bf79cba24b58b3e41852cd"
5. }

{
        "user" : "admin",
        "readOnly" : false,
        "pwd" : "995d2143e0bf79cba24b58b3e41852cd"
}

3、安全认证

db.auth("admin", ",�3_kj~00Opoo0+\/")

数据库安全认证。认证成功显示结果：

[plain] view plain copy print ?

1. {
2. "user" : "admin",
3. "readOnly" : false,
4. "pwd" : "995d2143e0bf79cba24b58b3e41852cd"
5. }

{
        "user" : "admin",
        "readOnly" : false,
        "pwd" : "995d2143e0bf79cba24b58b3e41852cd"
}

如果是认证用户，执行某些命令，可以看到正确执行结果，如下所示：

[plain] view plain copy print ?

1. db.system.users.find()
2. { "_id" : ObjectId("4ef940a13c1fc4613425acc8"), "user" : "admin", "readOnly" : false, "pwd" : "995d2143e0bf79cba24b58b3e41852cd" }

db.system.users.find()
{ "_id" : ObjectId("4ef940a13c1fc4613425acc8"), "user" : "admin", "readOnly" : false, "pwd" : "995d2143e0bf79cba24b58b3e41852cd" }

否则，认证失败，则执行相关命令会提示错误：

[plain] view plain copy print ?

1. db.system.users.find()
2. error: {
3. "$err" : "unauthorized db:admin lock type:-1 client:127.0.0.1", "code" : 10057
4. }

db.system.users.find()
error: {
        "$err" : "unauthorized db:admin lock type:-1 client:127.0.0.1", "code" : 10057
}

4、为数据库写数据（同步到磁盘）加锁

db.runCommand({fsync:1,lock:1})
说明：

该操作已经对数据库上锁，不允许执行写数据操作，一般在执行数据库备份时有用。执行命令，结果示例如下：

[plain] view plain copy print ?

1. {
2. "info" : "now locked against writes, use db.$cmd.sys.unlock.findOne() to unlock",
3. "ok" : 1
4. }

{
        "info" : "now locked against writes, use db.$cmd.sys.unlock.findOne() to unlock",
        "ok" : 1
}

5、查看当前锁状态

db.currentOp()

说明：

查询结果如下所示：

[plain] view plain copy print ?

1. {
2. "inprog" : [ ],
3. "fsyncLock" : 1,
4. "info" : "use db.$cmd.sys.unlock.findOne() to terminate the fsync write/snapshot lock"
5. }

{
        "inprog" : [ ],
        "fsyncLock" : 1,
        "info" : "use db.$cmd.sys.unlock.findOne() to terminate the fsync write/snapshot lock"
}

其中，fsyncLock为1表示MongoDB的fsync进程（负责将写入改变同步到磁盘）不允许其他进程执行写数据操作

6、解锁

use admin
db.$cmd.sys.unlock.findOne()

说明：

执行解锁，结果如下所示：

[plain] view plain copy print ?

1. { "ok" : 1, "info" : "unlock requested" }

{ "ok" : 1, "info" : "unlock requested" }

可以执行命令查看锁状态：
db.currentOp()
状态信息如下：

[plain] view plain copy print ?

1. { "inprog" : [ ] }

{ "inprog" : [ ] }

说明当前没有锁，可以执行写数据操作。

（五）数据备份、恢复与迁移管理

1、备份全部数据库

mkdir testbak
cd testbak
mongodump

说明：默认备份目录及数据文件格式为./dump/[databasename]/[collectionname].bson
2、备份指定数据库
mongodump -d pagedb

说明：备份数据库pagedb中的数据。

3、备份一个数据库中的某个集合

mongodump -d pagedb -c page

说明：备份数据库pagedb的page集合。

4、恢复全部数据库

cd testbak
mongorestore --drop

说明：将备份的所有数据库恢复到数据库，--drop指定恢复数据之前删除原来数据库数据，否则会造成回复后的数据中数据重复。

5、恢复某个数据库的数据

cd testbak
mongorestore -d pagedb --drop
说明：将备份的pagedb的数据恢复到数据库。

6、恢复某个数据库的某个集合的数据

cd testbak
mongorestore -d pagedb -c page --drop
说明：将备份的pagedb的的page集合的数据恢复到数据库。

7、向MongoDB导入数据

mongoimport -d pagedb -c page --type csv --headerline --drop < csvORtsvFile.csv

说明：将文件csvORtsvFile.csv的数据导入到pagedb数据库的page集合中，使用cvs或tsv文件的列名作为集合的列名。需要注意的是，使用--headerline选项时，只支持csv和tsv文件。
--type支持的类型有三个：csv、tsv、json
其他各个选项的使用，可以查看帮助：

[plain] view plain copy print ?

1. mongoimport --help
2. options:
3. --help produce help message
4. -v [ --verbose ] be more verbose (include multiple times for more
5. verbosity e.g. -vvvvv)
6. -h [ --host ] arg mongo host to connect to ( /s1,s2 for sets)
7. --port arg server port. Can also use --host hostname:port
8. --ipv6 enable IPv6 support (disabled by default)
9. -u [ --username ] arg username
10. -p [ --password ] arg password
11. --dbpath arg directly access mongod database files in the given
12. path, instead of connecting to a mongod server -
13. needs to lock the data directory, so cannot be used
14. if a mongod is currently accessing the same path
15. --directoryperdb if dbpath specified, each db is in a separate
16. directory
17. -d [ --db ] arg database to use
18. -c [ --collection ] arg collection to use (some commands)
19. -f [ --fields ] arg comma separated list of field names e.g. -f name,age
20. --fieldFile arg file with fields names - 1 per line
21. --ignoreBlanks if given, empty fields in csv and tsv will be ignored
22. --type arg type of file to import. default: json (json,csv,tsv)
23. --file arg file to import from; if not specified stdin is used
24. --drop drop collection first
25. --headerline CSV,TSV only - use first line as headers
26. --upsert insert or update objects that already exist
27. --upsertFields arg comma-separated fields for the query part of the
28. upsert. You should make sure this is indexed
29. --stopOnError stop importing at first error rather than continuing
30. --jsonArray load a json array, not one item per line. Currently
31. limited to 4MB.

mongoimport --help
options:
  --help                  produce help message
  -v [ --verbose ]        be more verbose (include multiple times for more
                          verbosity e.g. -vvvvv)
  -h [ --host ] arg       mongo host to connect to ( /s1,s2 for sets)
  --port arg              server port. Can also use --host hostname:port
  --ipv6                  enable IPv6 support (disabled by default)
  -u [ --username ] arg   username
  -p [ --password ] arg   password
  --dbpath arg            directly access mongod database files in the given
                          path, instead of connecting to a mongod  server -
                          needs to lock the data directory, so cannot be used
                          if a mongod is currently accessing the same path
  --directoryperdb        if dbpath specified, each db is in a separate
                          directory
  -d [ --db ] arg         database to use
  -c [ --collection ] arg collection to use (some commands)
  -f [ --fields ] arg     comma separated list of field names e.g. -f name,age
  --fieldFile arg         file with fields names - 1 per line
  --ignoreBlanks          if given, empty fields in csv and tsv will be ignored
  --type arg              type of file to import.  default: json (json,csv,tsv)
  --file arg              file to import from; if not specified stdin is used
  --drop                  drop collection first
  --headerline            CSV,TSV only - use first line as headers
  --upsert                insert or update objects that already exist
  --upsertFields arg      comma-separated fields for the query part of the
                          upsert. You should make sure this is indexed
  --stopOnError           stop importing at first error rather than continuing
  --jsonArray             load a json array, not one item per line. Currently
                          limited to 4MB.

8、从向MongoDB导出数据

mongoexport -d pagedb -c page -q {} -f _id,title,url,spiderName,pubDate --csv > pages.csv
说明：将pagedb数据库中page集合的数据导出到pages.csv文件，其中各选项含义：
-f 指定cvs列名为_id,title,url,spiderName,pubDate
-q 指定查询条件
其他各个选项的使用，可以查看帮助：

[plain] view plain copy print ?

1. mongoexport --help
2. options:
3. --help produce help message
4. -v [ --verbose ] be more verbose (include multiple times for more verbosity e.g. -vvvvv)
5. -h [ --host ] arg mongo host to connect to ( /s1,s2 for sets)
6. --port arg server port. Can also use --host hostname:port
7. --ipv6 enable IPv6 support (disabled by default)
8. -u [ --username ] arg username
9. -p [ --password ] arg password
10. --dbpath arg directly access mongod database files in the given
11. path, instead of connecting to a mongod server -
12. needs to lock the data directory, so cannot be used
13. if a mongod is currently accessing the same path
14. --directoryperdb if dbpath specified, each db is in a separate directory
15. -d [ --db ] arg database to use
16. -c [ --collection ] arg collection to use (some commands)
17. -f [ --fields ] arg comma separated list of field names e.g. -f name,age
18. --fieldFile arg file with fields names - 1 per line
19. -q [ --query ] arg query filter, as a JSON string
20. --csv export to csv instead of json
21. -o [ --out ] arg output file; if not specified, stdout is used
22. --jsonArray output to a json array rather than one object per line

mongoexport --help
options:
  --help                  produce help message
  -v [ --verbose ]        be more verbose (include multiple times for more verbosity e.g. -vvvvv)
  -h [ --host ] arg       mongo host to connect to ( /s1,s2 for sets)
  --port arg              server port. Can also use --host hostname:port
  --ipv6                  enable IPv6 support (disabled by default)
  -u [ --username ] arg   username
  -p [ --password ] arg   password
  --dbpath arg            directly access mongod database files in the given
                          path, instead of connecting to a mongod  server -
                          needs to lock the data directory, so cannot be used
                          if a mongod is currently accessing the same path
  --directoryperdb        if dbpath specified, each db is in a separate directory
  -d [ --db ] arg         database to use
  -c [ --collection ] arg collection to use (some commands)
  -f [ --fields ] arg     comma separated list of field names e.g. -f name,age
  --fieldFile arg         file with fields names - 1 per line
  -q [ --query ] arg      query filter, as a JSON string
  --csv                   export to csv instead of json
  -o [ --out ] arg        output file; if not specified, stdout is used
  --jsonArray             output to a json array rather than one object per line

注意：

如果上面的选项-q指定一个查询条件，需要使用单引号括起来，如下所示：

[plain] view plain copy print ?

1. mongoexport -d page -c Article -q '{"spiderName": "mafengwoSpider"}' -f _id,title,content,images,publishDate,spiderName,url --jsonArray > mafengwoArticle.txt

mongoexport -d page -c Article -q '{"spiderName": "mafengwoSpider"}' -f _id,title,content,images,publishDate,spiderName,url --jsonArray > mafengwoArticle.txt

否则，就会出现下面的错误：

[plain] view plain copy print ?

1. ERROR: too many positional options

ERROR: too many positional options

（六）远程连接管理

1、基于mongo实现远程连接

[plain] view plain copy print ?

1. mongo -u admin -p admin 192.168.0.197:27017/pagedb

mongo -u admin -p admin 192.168.0.197:27017/pagedb

通过mongo实现连接，可以非常灵活的选择参数选项，参看命令帮助，如下所示：

[plain] view plain copy print ?

1. mongo --help
2. MongoDB shell version: 1.8.3
3. usage: mongo [options] [db address] [file names (ending in .js)]
4. db address can be:
5. foo foo database on local machine
6. 192.169.0.5/foo foo database on 192.168.0.5 machine
7. 192.169.0.5:9999/foo foo database on 192.168.0.5 machine on port 9999
8. options:
9. --shell run the shell after executing files
10. --nodb don't connect to mongod on startup - no 'db address'
11. arg expected
12. --quiet be less chatty
13. --port arg port to connect to
14. --host arg server to connect to
15. --eval arg evaluate javascript
16. -u [ --username ] arg username for authentication
17. -p [ --password ] arg password for authentication
18. -h [ --help ] show this usage information
19. --version show version information
20. --verbose increase verbosity
21. --ipv6 enable IPv6 support (disabled by default)

mongo --help
MongoDB shell version: 1.8.3
usage: mongo [options] [db address] [file names (ending in .js)]
db address can be:
  foo                   foo database on local machine
  192.169.0.5/foo       foo database on 192.168.0.5 machine
  192.169.0.5:9999/foo  foo database on 192.168.0.5 machine on port 9999
options:
  --shell               run the shell after executing files
  --nodb                don't connect to mongod on startup - no 'db address' 
                        arg expected
  --quiet               be less chatty
  --port arg            port to connect to
  --host arg            server to connect to
  --eval arg            evaluate javascript
  -u [ --username ] arg username for authentication
  -p [ --password ] arg password for authentication
  -h [ --help ]         show this usage information
  --version             show version information
  --verbose             increase verbosity
  --ipv6                enable IPv6 support (disabled by default)

2、基于MongoDB支持的javascript实现远程连接

当你已经连接到一个远程的MongoDB数据库服务器（例如，通过mongo连接到192.168.0.184），现在想要在这个会话中连接另一个远程的数据库服务器（192.168.0.197），可以执行如下命令：

[plain] view plain copy print ?

1. > var x = new Mongo('192.168.0.197:27017')
2. > var ydb = x.getDB('pagedb');
3. > use ydb
4. switched to db ydb
5. > db
6. ydb
7. > ydb.page.findOne()
8. {
9. "_id" : ObjectId("4eded6a5bf3bfa0014000003"),
10. "content" : "巴黎是浪漫的城市，可是...",
11. "pubdate" : "2006-03-19",
12. "title" : "巴黎：从布鲁塞尔赶到巴黎",
13. "url" : "http://france.bytravel.cn/Scenery/528/cblsegdbl.html"
14. }

> var x = new Mongo('192.168.0.197:27017')
> var ydb = x.getDB('pagedb');
> use ydb
switched to db ydb
> db
ydb
> ydb.page.findOne()
{
        "_id" : ObjectId("4eded6a5bf3bfa0014000003"),
        "content" : "巴黎是浪漫的城市，可是...",
        "pubdate" : "2006-03-19",
        "title" : "巴黎：从布鲁塞尔赶到巴黎",
        "url" : "http://france.bytravel.cn/Scenery/528/cblsegdbl.html"
}

上述通过MongoDB提供的JavaScript脚本，实现对另一个远程数据库服务器进行连接，操作指定数据库pagedb的page集合。

如果启用了安全认证模式，可以在获取数据库连接实例时，指定认证账号，例如：

[plain] view plain copy print ?

1. > var x = new Mongo('192.168.0.197:27017')
2. > var ydb = x.getDB('pagedb', 'shirdrn', '(jkfFS$343$_\=\,.F@3');
3. > use ydb
4. switched to db ydb