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NOSQL and CAP
Theorem
NOSQL
NOSQL - Not Only SQL
SQL (and with it relational databases) have
dominated the database market for the last 30
years.
Relational databases offer an appealing
compromise between performance and the
ACID principles making them reliable and
performant.
The NOSQL movement is a push for nonrelational databases in circumstances that
traditional databases are failing.
http://blog.agroknow.com/?p=3854
NOSQL Variety
There isn't one type of NOSQL database.
NOSQL is defined by what it isn't.
Is CSV NOSQL? Sure (but most wouldn't call it that).
This week, we'll be talking about different Non-SQL databases, how
to use them, and their performance and other tradeoffs.
One of the biggest tradeoffs (that we have mentioned before) are
related to the CAP theorem.
CAP Theorem - Pick 2
Consistency means that each client
always has the same view of the data
Availability means that all clients can
always read and write
Partition tolerance means that the
system works well across physical
network partitions.
http://dba.stackexchange.com/questions/18435
/cap-theorem-vs-base-nosql
What CAP properties do
traditional, relational databases
optimize?
1. Consistency
2. Availability
3. Partition Tolerance
4. My Project 5 implementation is terrible, so None.
http://blog.flux7.c
om/blogs/nosql/c
ap-theorem-whydoes-it-matter
Types of Databases
Relational - (MySQL, Postgres, SQLite) stores data in rigid schemas and because of that an service
complicated queries (involving joins) quickly
Column-Based - (Google's BigTable, Apache's Hbase) stores huge amounts of data efficiently
Key-Value - (Amazon's DynamoDB, Facebook's Cassandra) meant for extremely fast retrievals of small
amounts of information
Document-Stores - (MongoDB, CouchDB) used as an alternative to relational tables with less rigidity and
hierarchical structured objects
Graph-Based - (Neo4J, GraphBase) stores billions of nodes and the edges between them for efficient
network/graph traversals.
These types are neither exclusive, nor comprehensive, and some DBMSs transcend each category.
Why you should not use NOSQL
SQL is well understood, interoperable between DBMSs, performant
for many circumstances, and stable.
Almost every different NOSQL DBMS has its own language, data
format restrictions, hardware/OS compatibilities issues, and quirks.
Most of the time, a relational database (like SQLite) is a simpler,
faster and better than NOSQL alternatives.
But, there are times when NOSQL is better, but I want to combat
some of the hype. NOSQL is generally built for scale, but most of the
time, you don't need scale, or you can shift when you do.