2. Mongo Shell

1. Mongo shell 简介

Mongo shell 是与MongoDB进行交互的 JavaScript接口，Mongo shell既可以对MongoDB进行CRUD（增删改查）操作，也可以执行对MongoDB的管理操作，如关闭MongoDB数据库等。

1.1 启动Mongo shell

1. 进入MongDB安装目录（确保MongoDB服务进程已开启）：

   cd <mongodb installation dir>
   

2. 输入如下命令：

   ./bin/mongo
   

运行示例：

[xinhuan@MacBook-Pro] ~$ cd /usr/local/Cellar/mongodb/3.4.7/
[xinhuan@MacBook-Pro] 3.4.7$ ./bin/mongo
MongoDB shell version v3.4.7
connecting to: mongodb://127.0.0.1:27017
MongoDB server version: 3.4.7
Server has startup warnings: 
2017-09-05T23:05:49.851+0800 I CONTROL  [initandlisten] 
2017-09-05T23:05:49.851+0800 I CONTROL  [initandlisten] ** WARNING: Access control is not enabled for the database.
2017-09-05T23:05:49.851+0800 I CONTROL  [initandlisten] **          Read and write access to data and configuration is unrestricted.
2017-09-05T23:05:49.851+0800 I CONTROL  [initandlisten] 
2017-09-05T23:05:49.851+0800 I CONTROL  [initandlisten] 
2017-09-05T23:05:49.851+0800 I CONTROL  [initandlisten] ** WARNING: soft rlimits too low. Number of files is 256, should be at least 1000

2. Mongo shell 操作

2.1 db — 查看当前正在使用的数据库

db

运行示例如下，test数据库是默认数据库

> db
test

2.2 use — 切换数据库

use <databa>

切换到MyCollection数据库，如过MyCollection不存在，则会自动创建

> use MyCollection
switched to db MyCollection

2.3 help— Mongo shell 帮助命令

help

在 Mongo shell 中输入help

> help
    db.help()                    help on db methods
    db.mycoll.help()             help on collection methods
    sh.help()                    sharding helpers
    rs.help()                    replica set helpers
    help admin                   administrative help
    help connect                 connecting to a db help
    help keys                    key shortcuts
    help misc                    misc things to know
    help mr                      mapreduce

    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
    show logs                    show the accessible logger names
    show log [name]              prints out the last segment of log in memory, 'global' is default
    use <db_name>                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

2.4 show — 查询相关信息

• show dbs或者show databases — 查看数据库

  > show dbs
  admin  0.000GB
  local  0.000GB
  

• show collections — 查看当前数据库中的集合（collection）

  > use admin
  switched to db admin
  > show collections
  system.version
  

  > use local
  switched to db local
  > show collections
  startup_log
  

• show log [name]— 查看日志，name的默认值为gloable

  > show log
  2017-09-05T23:05:49.291+0800 I CONTROL  [initandlisten] MongoDB starting : pid=948 port=27017 dbpath=/usr/local/var/mongodb 64-bit host=MacBook-Pro.local
  2017-09-05T23:05:49.291+0800 I CONTROL  [initandlisten] db version v3.4.7
  2017-09-05T23:05:49.291+0800 I CONTROL  [initandlisten] git version: cf38c1b8a0a8dca4a11737581beafef4fe120bcd
  2017-09-05T23:05:49.291+0800 I CONTROL  [initandlisten] OpenSSL version: OpenSSL 1.0.2l  25 May 2017
  2017-09-05T23:05:49.291+0800 I CONTROL  [initandlisten] allocator: system
  2017-09-05T23:05:49.291+0800 I CONTROL  [initandlisten] build environment:
  2017-09-05T23:05:49.291+0800 I CONTROL  [initandlisten]     distarch: x86_64
  2017-09-05T23:05:49.291+0800 I CONTROL  [initandlisten]     target_arch: x86_64
  2017-09-05T23:05:49.291+0800 I CONTROL  [initandlisten] options: { config: "/usr/local/etc/mongod.conf", net: { bindIp: "127.0.0.1" }, storage: { dbPath: "/usr/local/var/mongodb" }, systemLog: { destination: "file", logAppend: true, path: "/usr/local/var/log/mongodb/mongo.log" } }
  2017-09-05T23:05:49.292+0800 I -        [initandlisten] Detected data files in /usr/local/var/mongodb created by the 'wiredTiger' storage engine, so setting the active storage engine to 'wiredTiger'.
  2017-09-05T23:05:49.292+0800 I STORAGE  [initandlisten] wiredtiger_open config: create,cache_size=3584M,session_max=20000,eviction=(threads_min=4,threads_max=4),config_base=false,statistics=(fast),log=(enabled=true,archive=true,path=journal,compressor=snappy),file_manager=(close_idle_time=100000),checkpoint=(wait=60,log_size=2GB),statistics_log=(wait=0),
  2017-09-05T23:05:49.877+0800 I FTDC     [initandlisten] Initializing full-time diagnostic data capture with directory '/usr/local/var/mongodb/diagnostic.data'
  2017-09-05T23:05:49.878+0800 I NETWORK  [thread1] waiting for connections on port 27017
  2017-09-05T23:08:13.532+0800 I NETWORK  [thread1] connection accepted from 127.0.0.1:51118 #1 (1 connection now open)
  2017-09-05T23:08:13.533+0800 I NETWORK  [conn1] received client metadata from 127.0.0.1:51118 conn1: { application: { name: "MongoDB Shell" }, driver: { name: "MongoDB Internal Client", version: "3.4.7" }, os: { type: "Darwin", name: "Mac OS X", architecture: "x86_64", version: "16.7.0" } }
  

2.5 db.help() — 数据库帮助

> db.help()
DB methods:
    db.adminCommand(nameOrDocument) - switches to 'admin' db, and runs command [ just calls db.runCommand(...) ]
    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.createView(name, viewOn, [ { $operator: {...}}, ... ], { viewOptions } )
    db.createUser(userDocument)
    db.currentOp() displays currently executing operations in the db
    db.dropDatabase()
    db.fsyncLock() flush data to disk and lock server for backups
    db.fsyncUnlock() unlocks server following a db.fsyncLock()
    db.getCollection(cname) same as db['cname'] or db.cname
    db.getCollectionInfos([filter]) - returns a list that contains the names and options of the db's collections
    db.getCollectionNames()
    db.getLastError() - just returns the err msg string
    db.getLastErrorObj() - return full status object
    db.getLogComponents()
    db.getMongo() get the server connection object
    db.getMongo().setSlaveOk() allow queries on a replication slave server
    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.getWriteConcern() - returns the write concern used for any operations on this db, inherited from server object if set
    db.hostInfo() get details about the server's host
    db.isMaster() check replica primary status
    db.killOp(opid) kills the current operation in the db
    db.listCommands() lists all the db commands
    db.loadServerScripts() loads all the scripts in db.system.js
    db.logout()
    db.printCollectionStats()
    db.printReplicationInfo()
    db.printShardingStatus()
    db.printSlaveReplicationInfo()
    db.dropUser(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.setLogLevel(level,<component>)
    db.setProfilingLevel(level,<slowms>) 0=off 1=slow 2=all
    db.setWriteConcern( <write concern doc> ) - sets the write concern for writes to the db
    db.unsetWriteConcern( <write concern doc> ) - unsets the write concern for writes to the db
    db.setVerboseShell(flag) display extra information in shell output
    db.shutdownServer()
    db.stats()
    db.version() current version of the server

2.6 db.collection.help() — 集合帮助

> db.collection.help()
DBCollection help
    db.collection.find().help() - show DBCursor help
    db.collection.bulkWrite( operations, <optional params> ) - bulk execute write operations, optional parameters are: w, wtimeout, j
    db.collection.count( query = {}, <optional params> ) - count the number of documents that matches the query, optional parameters are: limit, skip, hint, maxTimeMS
    db.collection.copyTo(newColl) - duplicates collection by copying all documents to newColl; no indexes are copied.
    db.collection.convertToCapped(maxBytes) - calls {convertToCapped:'collection', size:maxBytes}} command
    db.collection.createIndex(keypattern[,options])
    db.collection.createIndexes([keypatterns], <options>)
    db.collection.dataSize()
    db.collection.deleteOne( filter, <optional params> ) - delete first matching document, optional parameters are: w, wtimeout, j
    db.collection.deleteMany( filter, <optional params> ) - delete all matching documents, optional parameters are: w, wtimeout, j
    db.collection.distinct( key, query, <optional params> ) - e.g. db.collection.distinct( 'x' ), optional parameters are: maxTimeMS
    db.collection.drop() drop the collection
    db.collection.dropIndexes()
    db.collection.ensureIndex(keypattern[,options]) - DEPRECATED, use createIndex() instead
    db.collection.explain().help() - show explain help
    db.collection.reIndex()
    db.collection.find([query],[fields]) - query is an optional query filter. fields is optional set of fields to return.
                                                  e.g. db.collection.find( {x:77} , {name:1, x:1} )
    db.collection.find(...).count()
    db.collection.find(...).limit(n)
    db.collection.find(...).skip(n)
    db.collection.find(...).sort(...)
    db.collection.findOne([query], [fields], [options], [readConcern])
    db.collection.group( { key : ..., initial: ..., reduce : ...[, cond: ...] } )
    db.collection.insert(obj)
    db.collection.insertOne( obj, <optional params> ) - insert a document, optional parameters are: w, wtimeout, j
    db.collection.insertMany( [objects], <optional params> ) - insert multiple documents, optional parameters are: w, wtimeout, j
    db.collection.mapReduce( mapFunction , reduceFunction , <optional params> )
    db.collection.aggregate( [pipeline], <optional params> ) - performs an aggregation on a collection; returns a cursor
    db.collection.remove(query)
    db.collection.replaceOne( filter, replacement, <optional params> ) - replace the first matching document, optional parameters are: upsert, w, wtimeout, j
    db.collection.renameCollection( newName , <dropTarget> ) renames the collection.
    db.collection.runCommand( name , <options> ) runs a db command with the given name where the first param is the collection name
    db.collection.save(obj)
    ...

2.7 db.<collection>.find().<method> — 游标(cursor)帮助

> db.collection.find().help()
find(<predicate>, <projection>) modifiers
    .sort({...})
    .limit(<n>)
    .skip(<n>)
    .batchSize(<n>) - sets the number of docs to return per getMore
    .collation({...})
    .hint({...})
    .readConcern(<level>)
    .readPref(<mode>, <tagset>)
    .count(<applySkipLimit>) - total # of objects matching query. by default ignores skip,limit
    .size() - total # of objects cursor would return, honors skip,limit
    .explain(<verbosity>) - accepted verbosities are {'queryPlanner', 'executionStats', 'allPlansExecution'}
    .min({...})
    .max({...})
    .maxScan(<n>)
    .maxTimeMS(<n>)
    .comment(<comment>)
    .snapshot()
    .tailable(<isAwaitData>)
    .noCursorTimeout()
    .allowPartialResults()
    .returnKey()
    .showRecordId() - adds a $recordId field to each returned object

Cursor methods
    .toArray() - iterates through docs and returns an array of the results
    .forEach(<func>)
    .map(<func>)
    .hasNext()
    .next()
    .close()
    .objsLeftInBatch() - returns count of docs left in current batch (when exhausted, a new getMore will be issued)
    .itcount() - iterates through documents and counts them
    .getQueryPlan() - get query plans associated with shape. To get more info on query plans, call getQueryPlan().help().
    .pretty() - pretty print each document, possibly over multiple lines