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

Nosql: non-relational, distributed, does not provide ACID

Simple data model

Separation of metadata and application data

Weak consistency

Advantages:

Avoid unnecessary complexity

High throughput

High-level scalability and low-end hardware clusters

Do not use object-relational mapping

Disadvantages:

ACID feature is not supported

Simple function

There is no unified data query model

ACID:atomicity atomicity, consistency consistency, isolation isolation, durability persistence

Nosql classification:

Column database (managed by column)

Key value storage

Document database (each line is treated as an entity, a separate file)

A graph storage database (a graph storage object with complex relationships), which is used to store complex relationships between people on social networking sites.

Data Storage Model of nosql

Column database (managed by column)

Data model: data is stored in columns, and the same column of data is stored together

Advantages: fast search, strong expansibility, easy to realize distributed

Disadvantages: the function is limited compared to sql

Application scenarios: distributed file system or distributed storage

Examples: bigtable, cassandra, HBase, hypertable (massive data storage)

Running on a distributed file system

Key-value storage (data model: key-value storage)

Advantage: find it quickly

Disadvantages: data is unstructured and is usually treated only as string or binary data

Application scenarios: content caching

Examples: redis, dynamo

Document database (each line is treated as an entity, a separate file)

Data model: similar to the key-value model, but value points to structured data, with multiple key-value pairs with a container attached to it

Advantages: the data format is not strict and there is no need to define the structure in advance

Adding a field does not need to change its data structure

Disadvantages: low query performance, lack of uniform query syntax

Application scenario: web application

Examples: MongoDB, couchDB

A graph storage database (a graph storage object with complex relationships), which is used to store complex relationships between people on social networking sites.

Data model: Graph structure model

Advantages: using graph structure correlation algorithm, × × × can meet the application requirements of special scenarios.

Disadvantages: it is difficult to achieve distribution, and the function is oriented.

Application scenarios: social network, recommendation system, relationship graph

Example: Neo4J

Mongodb:scalable (Extensible) high-performance (High performance) open source schema free document nosql

Schema free: no need to create data structures beforehand

Read and write in memory

Support for scalability: replication, automatic sharding

Suitable for: web site, cache, high scalability, high volume,low value

Installation of mongodb: rpm package installation is recommended here

Rpm package address: https://repo.mongodb.org/yum/redhat, choose your own version to download

Yum-y localinstall * .rpm

Mkdir-p / mongodb/data: create a data directory and modify the data directory path in the configuration file

Usermod-d / mongodb/data mongod

Chown-R mongod:mongod / mongodb/data: modify the master group of the data catalog

Finally, simply modify the information of the configuration file (data directory, log directory, etc.)

Finally, you can start mongod.

Service mongod start

Check the log record and find the following warning:

Cat / var/log/mongodb/mongod.log checks the log and reports an error as follows:

* * WARNING: soft rlimits too low. Rlimits set to 1024 processes, 64000 files.

Number of processes should be at least 32000: 0.5 times number of files.

Reference: http://blog.csdn.net/kk185800961/article/details/45613267

Mongodb current limit: 1024 processes, 64000 files

Mongodb recommended requirement: processes = 0.5*files=32000 (at least)

So you need to change the processes from 1024 to 32000 or greater.

Modify the configuration file / etc/security/limits.conf to add configuration information:

# for mongodb#

Mongod soft nofile 64000

Mongod hard nofile 64000

Mongod soft nproc 32000

Mongod hard nproc 32000

Then restart mongod, check the log record again, and find that there is no warning, so the installation of mongodb is successful

Simple grud operation of mongodb:

Help (see 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 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

View all libraries: show dbs

View all collections (tables in mysql, collections in mongodb): show collections

Switch library: use huangdb (no need to define it before, just use the library)

Insert data into the collection huangcoll: db.huangcoll.insert ({Name: "huang"})

View the data of the collection: db.huangcoll.find (): this is to view all the data of the collection huangcoll

Find data by criteria: db.huangcoll.find ({Name: "huang"}): find documents whose Name is huang

Create index: db.huangcoll.ensureIndex ({Name:1}): create an index on the field Name

View index: db.huangcoll.getIndexes (): view all indexes under the current collection

For more mongo command operations, refer to the documentation:

Https://docs.mongodb.com/manual/crud/

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