Shulou(Shulou.com)06/01 Report--

It is well known that MongoDB is a NoSQL non-database system, that is, a database can contain multiple sets (Collection), each set corresponding to the table in the relational database; and each set can store a set of records identified by the column, the column can be freely defined, very flexible, the set of entities identified by a set of columns corresponds to the rows in the relational database table. The following is to understand the basic functions and behavior of DBMS provided by MongoDB by familiarizing yourself with the basic management commands of MongoDB.

0) installation of MongoDB

[root@centos6-vm01 ~] # curl-O https://fastdl.mongodb.org/linux/mongodb-linux-x86_64-3.0.6.tgz

[root@centos6-vm01] # tar-zxvf mongodb-linux-x86_64-3.0.6.tgz

[root@centos6-vm01] # mv mongodb-linux-x86_64-3.0.6 / / usr/local/mongodb

[root@centos6-vm01 ~] # vim / etc/profile

.

Export PATH=$PATH:/usr/local/mongodb/bin/

[root@centos6-vm01 ~] # source / etc/profile

Start mongodb

[root@centos6-vm01] # mkdir-p / data/db

[root@centos6-vm01 ~] # cd / usr/local/mongodb/bin/

[root@centos6-vm01 bin] #. / mongod &

[root@centos6-vm01 bin] # lsof-iRose 27017

COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME

Mongod 24304 root 5U IPv4 187360 0t0 TCP *: 27017 (LISTEN)

Mongod 24304 root 12u IPv4 187456 0t0 TCP localhost:27017- > localhost:48742 (ESTABLISHED)

Mongo 24319 root 3u IPv4 187455 0t0 TCP localhost:48742- > localhost:27017 (ESTABLISHED)

Connection mongodb reports an error:

Failed global initialization: BadValue Invalid or no user locale set. Please ensure LANG and/or LC_* environment variables are set correctly.

Solution:

[root@centos6-vm01 ~] # vim / etc/profile

.

Export LC_ALL=C

[root@centos6-vm01 ~] # source / etc/profile

1) MongoDB Command help system

After installing MongoDB, start the server process (mongod), and you can manage and monitor the MongoDB through the client command mongo. Take a look at MongoDB's command help system:

[root@centos6-vm01 ~] # mongo

MongoDB shell version: 3.0.6

Connecting to: test

Welcome to the MongoDB shell.

For interactive help, type "help".

For more comprehensive documentation, see

Http://docs.mongodb.org/

Questions? Try the support group

Http://groups.google.com/group/mongodb-user

Server has startup warnings:

2018-01-02T23:24:23.304+0000 I CONTROL [initandlisten] WARNING: You are running this process as the root user, which is not recommended.

2018-01-02T23:24:23.304+0000 I CONTROL [initandlisten]

2018-01-02T23:24:23.307+0000 I CONTROL [initandlisten]

2018-01-02T23:24:23.307+0000 I CONTROL [initandlisten] WARNING: / sys/kernel/mm/transparent_hugepage/enabled is' always'.

2018-01-02T23:24:23.307+0000 I CONTROL [initandlisten] We suggest setting it to 'never'

2018-01-02T23:24:23.307+0000 I CONTROL [initandlisten]

2018-01-02T23:24:23.307+0000 I CONTROL [initandlisten] WARNING: / sys/kernel/mm/transparent_hugepage/defrag is' always'.

2018-01-02T23:24:23.307+0000 I CONTROL [initandlisten] * * We suggest setting it to 'never'

2018-01-02T23:24:23.307+0000 I CONTROL [initandlisten]

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 namesshow collections show collections in current databaseshow users show users in current databaseshow profile show most recent system.profile entries with time > = 1msshow logs show the accessible logger namesshow log [name] prints out the last segment of log in memory 'global' is defaultuse set current databasedb.foo.find () list objects in collection foodb.foo.find ({a: 1}) list objects in foo where a = = 1it result of the last line evaluated Use to further iterateDBQuery.shellBatchSize = x set default number of items to display on shellexit quit the mongo shell

This is the list of commands at the top level of MongoDB, which mainly tells us some abstract categories related to managing the database: database operation help, collection operation help, management help. If you want to learn more about the help commands for database operations, you can use db.help () directly, as follows:

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.createUser (userDocument)

Db.currentOp () displays currently executing operations in the db

Db.dropDatabase ()

Db.eval ()-deprecated

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 ()

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,)

Db.setProfilingLevel (level,) 0=off 1=slow 2=all

Db.setWriteConcern ()-sets the write concern for writes to the db

Db.unsetWriteConcern ()-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

The basic commands for managing and manipulating the database can be obtained from above. If you want more and the detailed usage of each command, you can use the db.listCommands () query listed above.

Another basic thing is to operate, manage, and monitor the collection of specified databases, which can be obtained by querying db.mycoll.help ():

Db.mycoll.help ()

DBCollection help

Db.mycoll.find (). Help ()-show DBCursor help

Db.mycoll.count ()

Db.mycoll.copyTo (newColl)-duplicates collection by copying all documents to newColl; no indexes are copied.

Db.mycoll.convertToCapped (maxBytes)-calls {convertToCapped:'mycoll', size:maxBytes}} command

Db.mycoll.dataSize ()

Db.mycoll.distinct (key)-e.g. Db.mycoll.distinct ('x')

Db.mycoll.drop () drop the collection

Db.mycoll.dropIndex (index)-e.g. Db.mycoll.dropIndex ("indexName") or db.mycoll.dropIndex ({"indexKey": 1})

Db.mycoll.dropIndexes ()

Db.mycoll.ensureIndex (keypattern [, options])

Db.mycoll.explain (). Help ()-show explain help

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 ({XRU 77}, {name:1, XRV 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 () getDB object associated with collection

Db.mycoll.getPlanCache () get query plan cache associated with collection

Db.mycoll.getIndexes ()

Db.mycoll.group ({key:..., initial:..., reduce:... [, cond:...]})

Db.mycoll.insert (obj)

Db.mycoll.mapReduce (mapFunction, reduceFunction,)

Db.mycoll.aggregate ([pipeline],)-performs an aggregation on a collection; returns a cursor

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 ({scale: n, indexDetails: true/false, indexDetailsKey:, indexDetailsName:})

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])-instead of two flags, you can pass an object with fields: upsert, multi

Db.mycoll.validate ()-SLOW

Db.mycoll.getShardVersion ()-only for use with sharding

Db.mycoll.getShardDistribution ()-prints statistics about data distribution in the cluster

Db.mycoll.getSplitKeysForChunks ()-calculates split points over all chunks and returns splitter function

Db.mycoll.getWriteConcern ()-returns the write concern used for any operations on this collection, inherited from server/db if set

Db.mycoll.setWriteConcern ()-sets the write concern for writes to the collection

Db.mycoll.unsetWriteConcern ()-unsets the write concern for writes to the collection

The commands related to database and collection management are the most basic and commonly used, such as collection query, index operation and so on. Here are some common commands that are demonstrated by practical examples:

1. Basic orders

1) show dbs

Show the database on the current database server

2) use pagedb

Switch to the context of the specified database pagedb, in which you can manage pagedb databases, collections, etc.

3) show collections

Show all collections in the database (collection)

4) db.serverStatus ()

View the status of the database server.

Sometimes, by looking at the status of the database server, you can determine whether there is a problem with the database, and if there is a problem, such as data corruption, repair can be performed in a timely manner.

5) query the specified database statistics

Use fragment

Db.stats ()

An example of the query result is as follows:

Use fragment

Switched to db fragment

Db.stats ()

{

"db": "fragment"

"collections": 0

"objects": 0

"avgObjSize": 0

"dataSize": 0

"storageSize": 0

"numExtents": 0

"indexes": 0

"indexSize": 0

"fileSize": 0

"ok": 1

}

6) query the list of collection names contained in the specified database

Db.getCollectionNames ()

The results are as follows:

Db.getCollectionNames ()

[

17u

"baseSe"

"bytravel"

"daodao"

"go2eu"

"lotour"

"lvping"

"mafengwo"

"sina"

"sohu"

"system.indexes"

]

II. Basic DDL and DML

1) create a database

If you are used to relational databases, you may look for relevant commands to create the database. In MongoDB, you can switch to this database context directly through use dbname, and the system will automatically delay the creation of the database, for example:

Show dbs

Local 0.078GB

Use LuceneIndexDB

Switched to db LuceneIndexDB

Show dbs

Local 0.078GB

Db

LuceneIndexDB

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

WriteResult ({"nInserted": 1})

Show dbs

LuceneIndexDB 0.078GB

Local 0.078GB

It can be seen that after use specifies the database and inserts data into one of the specified sets, both the database and the collection are created.

2) Delete the database

You can delete the database directly using db.dropDatabase ().

3) create a collection

You can use the command db.createCollection (name, {size:..., capped:..., max:...}) to create a collection, as shown in the following example:

Db.createCollection ('replicationColletion', {' capped':true, 'size':10240,' max':17855200})

{"ok": 1}

Show collections

ReplicationColletion

StoreCollection

System.indexes

4) Delete the collection

To delete the collection, you can execute db.mycoll.drop ().

5) insert update record

Use the collection's save method directly, as follows:

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

WriteResult ({"nInserted": 1})

Update the record, using save will overwrite the original record value to achieve record update.

6) query a record

Use the findOne () function with the query condition as the parameter. Optionally, the system will randomly query to get a record that meets the condition (if the number of query results is greater than or equal to 1) the example is as follows:

Db.storeCollection.findOne ({'version':'3.5'})

{

"_ id": ObjectId ("5a4c1733f5c45f057ae82292")

"version": "3.5"

"segment": "e3ol6"

}

7) query multiple records

Using the find () function, the parameter specifies the query condition, and if no condition is specified, all records are queried.

8) Delete records

Using the collection's remove () method, the parameter is specified as the query condition, as shown in the following example:

Db.storeCollection.remove ({'version':'3.5'})

WriteResult ({"nRemoved": 2})

Db.storeCollection.findOne ()

Null

9) create an index

You can use the collection's ensureIndex (keypattern [, options]) method, as shown in the following example:

Use pagedb

Switched to db pagedb

Db.page.ensureIndex ({'title':1,' url':-1})

{

"createdCollectionAutomatically": true

"numIndexesBefore": 1

"numIndexesAfter": 2

"ok": 1

}

Db.system.indexes.find ()

{"v": 1, "key": {"_ id": 1}, "name": "id", "ns": "pagedb.page"}

{"v": 1, "key": {"title": 1, "url":-1}, "name": "title_1url-1", "ns": "pagedb.page"}

In the parameters of the ensureIndex method, the number 1 indicates ascending order and-1 indicates descending order.

Use db.system.indexes.find () to query all indexes.

10) query index

If we index the collection, we can implement the query through the collection's getIndexes () method, as shown in the following example:

Db.page.getIndexes ()

[

{

"v": 1

"key": {

"_ id": 1

}

"name": "id"

"ns": "pagedb.page"

}

{

"v": 1

"key": {

"title": 1

"url":-1

}

"name": "title_1url-1"

"ns": "pagedb.page"

}

]

Of course, if you need to query all the indexes in the system, you can use the db.system.indexes.find () function.

11) Delete index

Deleting an index gives two ways:

Db.mycoll.dropIndex (name)

2018-01-02T23:45:50.155+0000 E QUERY ReferenceError: name is not defined

At (shell): 1:21

Db.mycoll.dropIndexes ()

{"ok": 0, "errmsg": "ns not found"}

The first deletes all indexes of the specified collection by specifying the index name.

12) Index reconstruction

The index can be rebuilt through the collection's reIndex () method, as shown in the following example:

Db.page.reIndex ()

{

"nIndexesWas": 2

"nIndexes": 2

"indexes": [

{

"key": {

"_ id": 1

}

"name": "id"

"ns": "pagedb.page"

}

{

"key": {

"title": 1

"url":-1

}

"name": "title_1url-1"

"ns": "pagedb.page"

}

]

"ok": 1

}

13) count the number of records in the collection

Use fragment

Switched to db fragment

Db.baseSe.count ()

36749

The above counts the number of records in the baseSe collection of the database fragment.

14) query and count the number of result records

Use fragment

Switched to db fragment

Db.baseSe.find () .count ()

36749

Find () can provide query parameters, and then query and count the results. The above execution first queries the results according to the query conditions, and then counts the number of records in the baseSe result record set of the query database fragment.

15) query the currently available storage space for the collection of the specified database

Use fragment

Switched to db fragment

Db.baseSe.storageSize ()

142564096

16) query the storage space allocated by the collection of the specified database

Db.baseSe.totalSize ()

144096000

The above query results include the storage space allocated for the collection (data and its index storage).

III. Start and terminate

1) start normally

[root@centos6-vm01] # mongod-- dbpath / data/db-- logfile / var/mongo.log

Description: specify data storage directory and log directory

If you use secure authentication mode, you need to add-- auth option, such as:

[root@centos6-vm01] # mongod-- auth-- dbpath / data/db-- logfile / var/mongo.log

2) start in repair mode

[root@centos6-vm01] # mongod-- repair

Start the database in repair mode.

In fact, it is very likely that the database data is corrupted or the data state is inconsistent, resulting in the failure to start the MongoDB server normally. According to the startup information, you can see that it needs to be repaired. Or execute:

[root@centos6-vm01] # mongod-f / etc/mongodb.conf-- repair

3) terminate the server process

Db.shutdownServer ()

Terminates the database server process. Alternatively, you can simply kill the mongod process.

IV. Safety management

1) start in secure authentication mode

[root@centos6-vm01] # mongod-- auth-- dbpath / usr/mongo/data-- logfile / var/mongo.log

Use the-- auth option to start the mongod process to enable authentication mode.

Alternatively, you can modify / etc/mongodb.conf, set auth=true, and restart the mongod process.

2) add users

Db.createUser ({user: "admin", pwd: "1234 thanks qwer", roles: ["readWrite", "dbAdmin"]})

If the database user is added successfully, the result is as follows:

one

two

Db.createUser ({user: "admin", pwd: "1234 thanks qwer", roles: ["readWrite", "dbAdmin"]})

Successfully added user: {"user": "admin", "roles": ["readWrite", "dbAdmin"]}

3) Security certification

The premise is that you must enter the corresponding database of the user. The presence of 1 indicates success.

Db.auth ("admin", "1234 thanks thanks qwer")

Database security certification. The result of successful certification is displayed:

Use admin

Switched to db admin

Db.auth ("admin", "1234 thanks thanks qwer")

If you are an authenticated user, execute some commands, and you can see the correct execution results, as shown below:

Db.system.users.find ()

{"_ id": "fragment.admin", "user": "admin", "db": "fragment", "credentials": {"SCRAM-SHA-1": {"iterationCount": 10000, "salt": "/ QZtFAvcavqZIm15FmbToA==", "storedKey": "t91XZuIrnUYtuN1bGlobhNg58Roundw0 =", "serverKey": "vZLGW0nVpGSKfUHsS2RABOXhOb4="}, "roles": [{"role": "readWrite" "db": "fragment"}, {"role": "dbAdmin", "db": "fragment"}]}

4. lock the database by writing data (synchronizing to disk)

Db.runCommand ({fsync:1,lock:1})

Description: this operation has locked the database and is not allowed to write data. It is generally useful when performing database backups. Execute the command, and the result example is as follows:

Db.runCommand ({fsync:1,lock:1})

{

"info": "now locked against writes, use db.fsyncUnlock () to unlock"

"seeAlso": "http://dochub.mongodb.org/core/fsynccommand","

"ok": 1

}

5) View the current lock status

Db.currentOp ()

Description: the query results are as follows:

Db.currentOp ()

{

"inprog": []

"fsyncLock": true

"info": "use db.fsyncUnlock () to terminate the fsync write/snapshot lock"

}

Where a fsyncLock of 1 means that the fsync process of MongoDB (responsible for synchronizing write changes to disk) does not allow other processes to perform write data operations

6) unlock

Use admin

Db.$cmd.sys.unlock.findOne ()

Description: perform unlocking, and the result is as follows:

Use admin

Switched to db admin

Db.$cmd.sys.unlock.findOne ()

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

You can execute the command to view the lock status:

Db.currentOp ()

The status information is as follows:

Db.currentOp ()

{"inprog": []}

Indicates that there is currently no lock and you can perform write data operations.

5. Data backup, recovery and migration management

1) back up all databases

[root@centos6-vm01 ~] # mkdir testbak

[root@centos6-vm01 ~] # cd testbak

[root@centos6-vm01 ~] # mongodump

Description: the default backup directory and data file format is. / dump/ [databasename] / [collectionname] .bson

2) back up the specified database

[root@centos6-vm01] # mongodump-d pagedb

Description: back up the data in the database pagedb.

3) back up a collection in a database

[root@centos6-vm01] # mongodump-d pagedb-c page

Description: back up the page collection of database pagedb.

4) restore all databases

[root@centos6-vm01 ~] # cd testbak

[root@centos6-vm01] # mongorestore-- drop

Description: restore all backed-up databases to the database.-- drop specifies to delete the original database data before restoring the data, otherwise it will cause data duplication in the restored data.

5) restore the data of a database

[root@centos6-vm01 ~] # cd testbak

[root@centos6-vm01] # mongorestore-d pagedb-- drop

Description: restore the backed-up pagedb data to the database.

6) recover the data of a collection of a database

[root@centos6-vm01 ~] # cd testbak

[root@centos6-vm01] # mongorestore-d pagedb-c page-- drop

Description: restore the data of the page collection of the backed up pagedb to the database.

7) Import data to MongoDB

[root@centos6-vm01] # 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： [root@centos6-vm01 ~]# mongoimport --help Usage: mongoimport Import CSV, TSV or JSON data into MongoDB. If no file is provided, mongoimport reads from stdin. See http://docs.mongodb.org/manual/reference/program/mongoimport/ for more information. general options: --help print usage --version print the tool version and exit verbosity options: -v, --verbose more detailed log output (include multiple times for more verbosity, e.g. -vvvvv) --quiet hide all log output connection options: -h, --host= mongodb host to connect to (setname/host1,host2 for replica sets) --port= server port (can also use --host hostname:port) authentication options: -u, --username= username for authentication -p, --password= password for authentication --authenticationDatabase= database that holds the user's credentials --authenticationMechanism= authentication mechanism to use namespace options: -d, --db= database to use -c, --collection= collection to use input options: -f, --fields= comma separated list of field names, e.g. -f name,age --fieldFile= file with field names - 1 per line --file= file to import from; if not specified, stdin is used --headerline use first line in input source as the field list (CSV and TSV only) --jsonArray treat input source as a JSON array --type= input format to import: json, csv, or tsv (defaults to 'json') ingest options: --drop drop collection before inserting documents --ignoreBlanks ignore fields with empty values in CSV and TSV --maintainInsertionOrder insert documents in the order of their appearance in the input source -j, --numInsertionWorkers= number of insert operations to run concurrently (defaults to 1) --stopOnError stop importing at first insert/upsert error --upsert insert or update objects that already exist --upsertFields= comma-separated fields for the query part of the upsert --writeConcern= write concern options e.g. --writeConcern majority, --writeConcern '{w: 3, wtimeout: 500, fsync: true, j: true}' (defaults to 'majority') 8）从向MongoDB导出数据 [root@centos6-vm01 ~]# mongoexport -d pagedb -c page -q {} -f _id,title,url,spiderName,pubDate --csv >

Pages.csv

Description: export the data from the page collection in the pagedb database to a pages.csv file, where each option means:

-f specifies that the cvs column is named _ id,title,url,spiderName,pubDate

-Q specify query criteria

For the use of other options, you can see the help:

[root@centos6-vm01] # mongoexport-- help

Usage:

Mongoexport

Export data from MongoDB in CSV or JSON format.

See http://docs.mongodb.org/manual/reference/program/mongoexport/ for more information.

General options:

-- help print usage

-- version print the tool version and exit

Verbosity options:

-v,-- verbose more detailed log output (include multiple times for more verbosity, e.g.-vvvvv)

-- quiet hide all log output

Connection options:

-h,-- host= mongodb host to connect to (setname/host1,host2 for replica sets)

-- port= server port (can also use-- host hostname:port)

Authentication options:

-u,-- username= username for authentication

-p,-- password= password for authentication

-- authenticationDatabase= database that holds the user's credentials

-- authenticationMechanism= authentication mechanism to use

Namespace options:

-d,-- db= database to use

-c,-- collection= collection to use

Output options:

-f,-- fields= comma separated list of field names (required for exporting CSV) e.g.-f "name,age"

-- fieldFile= file with field names-1 per line

-- type= the output format, either json or csv (defaults to 'json')

-o,-- out= output file; if not specified, stdout is used

-- jsonArray output to a JSON array rather than one object per line

-- pretty output JSON formatted to be human-readable

Querying options:

-Q,-- query= query filter, as a JSON string, e.g.,'{x: {$gt:1}}'

-k,-- slaveOk allow secondary reads if available (default true)

-forceTableScan force a table scan (do not use $snapshot)

-- skip= number of documents to skip

-- limit= limit the number of documents to export

-- sort= sort order, as a JSON string, e.g.'{XRO 1}'

Note: if the above option-Q specifies a query condition, it needs to be enclosed in single quotation marks, as follows:

[root@centos6-vm01 ~] # mongoexport-d page-c Article-Q'{"spiderName": "mafengwoSpider"}'- f _ id,title,content,images,publishDate,spiderName,url-- jsonArray > mafengwoArticle.txt

2018-01-03T08:12:41.234+0800 connected to: localhost

2018-01-03T08:12:41.234+0800 exported 0 records

[root@centos6-vm01 ~] # ll mafengwoArticle.txt

-rw-r--r--. 1 root root 3 Jan 3 00:12 mafengwoArticle.txt

Otherwise, the following error occurs:

one

ERROR: too many positional options

VI. Remote connection management

1) remote connection based on mongo

[root@centos6-vm01 ~] # mongo 192.168.10.220:27017/pagedb

Or

[root@centos6-vm01] # mongo 192.168.10.220:27017/pagedb-ukevin-p123456kevin

To connect through mongo, you can choose parameter options flexibly. See the command help, as shown below:

[root@centos6-vm01] # mongo-- help

MongoDB shell version: 3.0.6

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

-- norc will not run the ".mongorc.js" file on

Start up

-- quiet be less chatty

-- port arg port to connect to

-- host arg server to connect to

-- eval arg evaluate javascript

-h [--help] show this usage information

-- version show version information

-- verbose increase verbosity

-- ipv6 enable IPv6 support (disabled by default)

Authentication Options:

-u [--username] arg username for authentication

-p [--password] arg password for authentication

-- authenticationDatabase arg user source (defaults to dbname)

-- authenticationMechanism arg authentication mechanism

-- gssapiServiceName arg (= mongodb) Service name to use when authenticating

Using GSSAPI/Kerberos

-- gssapiHostName arg Remote host name to use for purpose of

GSSAPI/Kerberos authentication

File names: a list of files to run. Files have to end in .js and will exit after unless-- shell is specified

2) remote connection based on javascript supported by MongoDB

When you have connected to a remote MongoDB database server (for example, connect to 192.168.0.184 through mongo) and now want to connect to another remote database server (192.168.0.197) in this session, you can execute the following command:

Var x = new Mongo ('192.168.10.220purl 27017')

Var ydb = x.getDB ('pagedb')

Use ydb

Switched to db ydb

Db

Ydb

Ydb.page.findOne ()

{

"_ id": ObjectId ("4eded6a5bf3bfa0014000003")

Content: Paris is a romantic city, but.

"pubdate": "2006-03-19"

"title": Paris: from Brussels to Paris

"url": "http://france.bytravel.cn/Scenery/528/cblsegdbl.html""

}

The above uses the JavaScript script provided by MongoDB to connect to another remote database server and manipulate the page collection of the specified database pagedb.

If secure authentication mode is enabled, you can specify the authentication account when obtaining the database connection instance, for example:

Var x = new Mongo ('192.168.0.197purl 27017')

Var ydb = x.getDB ('pagedb',' shirdrn','(jkfFS$343 $_\ =\, .F @ 3')

Use ydb

Switched to db ydb

Welcome to subscribe "Shulou Technology Information " to get latest news, interesting things and hot topics in the IT industry, and controls the hottest and latest Internet news, technology news and IT industry trends.