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

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Distributed system theory:

CAP:

Consistency

Usability

Partition fault tolerance

MongoDB:

Installation

Crud

Indexes

Replica set

Slice

NoSQL: non-relational, distributed, does not provide ACID functionality

Technical features:

1. Simple data model

2. Separation of metadata and application data (stored on different servers)

3. Weak consistency

Advantages:

1. Avoid unnecessary complexity

2. High throughput

3. High-level scalability and low-end hardware cluster

4. Object-relational mapping is not applicable

Disadvantages:

1. ACID feature is not supported

2. Simple function

3. There is no unified data query model.

Classification:

NoSQL:

Key value storage

Column database

Document database

Schema database

SQL:

Mysql

Pgsql

Cache database system:

Memcache

CAP Theory: pick 2 from CAP

BASE theory:

Basic availability

Soft state

Final consistency

Cperfine Aazzo SQL (ensure consistency, availability)

C _ journal P: pessimistic locking mechanism (consistency, partition fault tolerance)

A,P:DNS

Data consistency model: strong consistency, weak consistency, final consistency

The realization technology of data consistency:

Quorum (legal number of votes) system NRW policy (concern)

N: number of copies

R: the minimum number of copies required to complete the read operation

W: the minimum number of copies required to complete the write operation

To ensure strong consistency: ringing W > N

At best, the ultimate consistency can only be guaranteed: rang W db.helpfunction () {print ("DB methods:"); print ("\ tdb.addUser (userDocument)"); print ("\ tdb.adminCommand (nameOrDocument)-switches to 'admin' db, and runs command [just calls db.runCommand (...)]"); print ("\ tdb.auth (username, password)"); print ("\ tdb.cloneDatabase (fromhost)") Print ("\ tdb.commandHelp (name) returns the help for the command"); print ("\ tdb.copyDatabase (fromdb, todb, fromhost)"); print ("\ tdb.createCollection (name, {size:..., capped:..., max:...})"); print ("\ tdb.currentOp () displays currently executing operations in the db"); print ("\ tdb.dropDatabase ()") Print ("\ tdb.eval (func, args) run code server-side"); print ("\ tdb.fsyncLock () flush data to disk and lock server for backups"); print ("\ tdb.fsyncUnlock () unlocks server following a db.fsyncLock ()"); print ("\ tdb.getCollection (cname) same as db ['cname'] or db.cname"); print ("\ tdb.getCollectionNames ()"); print ("\ tdb.getLastError ()-just returns the err msg string") Print ("\ tdb.getLastErrorObj ()-return full status object"); print ("\ tdb.getMongo () get the server connection object"); print ("\ tdb.getMongo (). SetSlaveOk () allow queries on a replication slave server"); print ("\ tdb.getName ()"); print ("\ tdb.getPrevError ()"); print ("\ tdb.getProfilingLevel ()-deprecated") Print ("\ tdb.getProfilingStatus ()-returns if profiling is on and slow threshold"); print ("\ tdb.getReplicationInfo ()"); print ("\ tdb.getSiblingDB (name) get the db at the same server as this one"); print ("\ tdb.hostInfo () get details about the server's host"); print ("\ tdb.isMaster () check replica primary status"); print ("\ tdb.killOp (opid) kills the current operation in the db") Print ("\ tdb.listCommands () lists all the db commands"); print ("\ tdb.loadServerScripts () loads all the scripts in db.system.js"); print ("\ tdb.logout ()"); print ("\ tdb.printCollectionStats ()"); print ("\ tdb.printReplicationInfo ()"); print ("\ tdb.printShardingStatus ()"); print ("\ tdb.printSlaveReplicationInfo ()"); print ("\ tdb.removeUser (username)") Print ("\ tdb.repairDatabase ()"); print ("\ tdb.resetError ()"); print ("\ tdb.runCommand (cmdObj) run a database command. If cmdObj is a string, turns it into {cmdObj: 1} "); print ("\ tdb.serverStatus () "); print ("\ tdb.setProfilingLevel (level,) 0=off 1=slow 2=all "); print ("\ tdb.setVerboseShell (flag) display extra information in shell output "); print ("\ tdb.shutdownServer () "); print ("\ tdb.stats () "); print ("\ tdb.version () current version of the server "); return _ magicNoPrint;}

Collection 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])-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 ({name:1, x db.mycoll.find 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.getIndexes () db.mycoll.group ({key:..., initial:..., reduce:. [ Cond:...]}) db.mycoll.insert (obj) 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])-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

Easy to use:

Using a database: (no need to create), and no need for collection to create

Db.collection.insert: insertin

Show collections: query collection

Db.collections.find (): query statement

Db.collections.update (): update

Db.collections.remove (): removin

Collection information:

Delete the collection:

View the database file:

Basic operations:

Show dbs: view all databases

Show collections: viewing collections

Show users: viewing users

Show profile:

Show logs: view a list of all logs

Show log [name]: view specific logs

Remote connection:

Mongo-host ip

Crud operation:

Create,read,update,delete

Although there is no table structure, you should put a collection for similar objects.

Query:

Db.users.find ({age: {$gt:18}}) .sort ({age:1}) query users whose age is greater than 18, and sort them in ascending order of age

Insert:

Db.users.insert (

{

Name:'suse'

Age:26

Status:'A'

Group: ['news','sports']

}

)

Update:

Db.coll.update (

{age: {$gt:18}}

{$set: {status:'A'}}

{multi:true} modify only the first eligible one when it is not specified

)

Delete:

Db.coll.delete (

{status:'D'}

)

Insert:

Only 20 are displayed in a batch. Enter it to continue.

Limit:

Delete:

Modify:

Advanced usage of find:

Db.collection.find (,)

Db.collection.count () returns the number of entries

Comparison operation:

$gt: greater than {field: {$gt:value}}

$gte: greater than or equal to {field: {$gte:value}}

$in: exists in {field: {$in: [value1,value2,...]}}

$lt: less than {field: {$lt:value}}

Lte: less than or equal to {field: {$lte:value}}

$ne: not equal to {field: {$ne:value}}

$nin: does not exist in {field: {$nin: [value1,value2...]}}

Greater than

Display the required fields:

Logical operation:

$or: or operation, {$or: [{expression1}, {expression2},...]}

$and: or operation, {$and: [{expression1}, {expression2},...]}

$not: or operation, {field: {$not: {operator-expression}

$nor: inverse operation, that is, returns documents that do not meet all the specified conditions, {$nor: [{expression1}, {expression2},...]}

And operation:

Element query:

If you want to select a document under conditions such as whether there is a field in the separated document, you need to use element operations.

$exists: selects documents according to the existence of the specified field. Syntax: {field: {$exists:}}. The specified value is' true''to return the document with the specified field, and 'false' to return the document without the specified field

$mod: a document in which the value of the specified field is modular and the rest is returned as the specified value. Syntax {field: {$mod: [divisor,remainder]}}

$type: returns the document whose value type of the specified field is the specified type. Syntax: {field: {$type:}}

Reinsert a piece of data:

Query:

Update:

The update proprietary operator roughly consists of: field,array,bitwise

Field:

$inc: increase the value of the specified field. Format:

Db.collection.update ({field:value}, {$nic: {field1:amount}}), where {field:value} is used to specify the selection criteria, and {$inc: {field1:amount}} is used to specify the field whose value is to be raised and the size of the amount

$rename: change the field name in the format {$rename: {:,:,...}}

$set: modify the value of the field to the newly specified value in the format db.collection.update ({field:value1}, {$set: {field2:value2}})

$unset: deletes the specified field in the format db.collection.update ({field:value1}, {$unset: {field1: ""}})

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