Redis noSQL database design example

This article explains how we made our article section on http://redis4you.com/articles.php.

We use same technics for programming examples section.

Before we do database design we need to see what data we will have and what are "relations" between the data.

For articles we have:

Article - contain name, description, filename, posting date.

Later we may decide to add more fields, but since Redis is schema-free this will be no problem.

Each Article may have zero, one or more tags.
Each tag may have zero, one or more articles.

Because Redis is key / value, we will need to decide what kind of lookups we will need to be able to to:

List all articles.
List single article, plus lising its tags.
By given tag(s), list all articles in it.

Database design:

We put all articles in hash keys such "art:1", "art:2" etc.

redis 127.0.0.1> hgetall "art:1"
1) "desc"
2) "How to use Redis for session handler in PHP in a way similar to msession or PostgreSQL sessions"
3) "file"
4) "001"
5) "name"
6) "Redis as session handler in PHP"

Hashes are memory optimized and uses much less memory than reguar keys. Also, when we need to add more data, we just add additional hash field.

Because we need to be able to show all articles, we do set "all:art".

redis 127.0.0.1> smembers "all:art"
1) "1"
2) "2"
3) "3"
4) "4"
5) "5"
6) "6"
7) "7"
8) "8"

Set took memory, but later is much more faster than "keys art:*".

For each article we do a set such "art:1:tags", "art:2:tags" etc., with tags this:

redis 127.0.0.1> smembers "art:1:tags"
1) "system administration"
2) "php"

However this is just to display the information. We will need single set for each tag too:

redis 127.0.0.1> smembers "tags:art:php"
1) "1"
2) "8"
redis 127.0.0.1> smembers "tags:art:system administration"
1) "1"
2) "2"
3) "5"
4) "6"
5) "7"
6) "8"

We choosed tags:art:XXX because we use same for code examples page.

Now we can display all articles in one set, but also we can do easily intersects of two or more sets too.

To add new article we will need to do following:

redis 127.0.0.1> hmset "art:9" "file" "009" "data" "2011-09-02"
OK
redis 127.0.0.1> hmset "art:9" "name" "Redis noSQL database design example"
OK
redis 127.0.0.1> hmset "art:9" "desc" "This article explains how we made our article section on http://redis4you.com/articles.php"
OK

redis 127.0.0.1> sadd "art:9:tags" "programming"
(integer) 1
redis 127.0.0.1> sadd "art:9:tags" "database design"
(integer) 1
redis 127.0.0.1> sadd "art:9:tags" "optimization"
(integer) 1

redis 127.0.0.1:1001[1]> sadd "tags:art:optimization" 9
(integer) 1
redis 127.0.0.1:1001[1]> sadd "tags:art:programming" 9
(integer) 1
redis 127.0.0.1:1001[1]> sadd "tags:art:database design" 9
(integer) 1

redis 127.0.0.1:1001[1]> sadd "all:art" 9

This is all. Now we need to program some code that do the visualization.

For comparisson we will show simple MySQL schema that do same data structure:

CREATE TABLE articles(
	id	int not null primary key,
	name	varchar(100),
	`desc`	varchar(100),
	`file`	varchar(3),
	data	date
);

CREATE TABLE articles_tags(
	id	int not null,
	tag	varchar(100) not null,
	primary key(
		id,
		tag
	)	
);

CREATE INDEX tag ON articles_tags(tag);

In this case MySQL way is very nice and clear, but because schema is fixed some future changes will be difficult to be implemented.

blog comments powered by Disqus

Redis noSQL database design example

Articles library

Redis as session handler in PHP

Lazy starter script on Linux such Redhat CentOS or Fedora

Redis vs Memcached comparison

Why RDBMS and SQL are difficult...

Seamless migration from one Redis server to another

Redis swap issue while save

Amazon EC2 and Amazon ElastiCache service

Understanding hash-max-zipmap-entries and 'hash of hashes' optimization

NoSQL database design example

Redis save and backup script

Postgres 9.1 foreign data wrapper interface

Redis high traffic connection issue

Redis too many open files error on high traffic sites

PHP Redis bug with PHP 5.4

Case Study: Using Redis intersect on very large sets

Getting started with Python and Redis on CentOS 6.X

GeoIP in Redis

Redis database file examination