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05.6.md

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5.6 NoSQL database

A NoSQL database provides a mechanism for storage and retrieval of data that use looser consistency models than relational database in order to achieve horizontal scaling and higher availability. Some authors refer to them as "Not only SQL" to emphasize that some NoSQL systems do allow SQL-like query language to be used.

As the C language of 21st century, Go has good support for NoSQL databases, and the popular NoSQL database including redis, mongoDB, Cassandra and Membase.

redis

redis is a key-value storage system like Memcached, it supports string, list, set and zset(ordered set) as it's value types.

There are some Go database drivers for redis:

I forked the last one and fixed some bugs, and use it in my short URL service(2 million PV every day).

Let's see how to use the driver that I forked to operate database:

package main

import (
	"github.com/astaxie/goredis"
	"fmt"
)

func main() {
	var client goredis.Client
	
	// Set the default port in Redis
	client.Addr = "127.0.0.1:6379"
	
	// string manipulation
	client.Set("a", []byte("hello"))
	val, _ := client.Get("a")
	fmt.Println(string(val))
	client.Del("a")

	// list operation
	vals := []string{"a", "b", "c", "d", "e"}
	for _, v := range vals {
		client.Rpush("l", []byte(v))
	}
	dbvals,_ := client.Lrange("l", 0, 4)
	for i, v := range dbvals {
		println(i,":",string(v))
	}
	client.Del("l")
}

We can see that it's quite easy to operate redis in Go, and it has high performance. Its client commands are almost the same as redis built-in commands.

mongoDB

mongoDB (from "humongous") is an open source document-oriented database system developed and supported by 10gen. It is part of the NoSQL family of database systems. Instead of storing data in tables as is done in a "classical" relational database, MongoDB stores structured data as JSON-like documents with dynamic schemas (MongoDB calls the format BSON), making the integration of data in certain types of applications easier and faster.

Figure 5.1 MongoDB compares to Mysql

The best driver for mongoDB is called mgo, and it is possible to be in the standard library in the future.

Here is the example:

package main

import (
    "fmt"
    "labix.org/v2/mgo"
    "labix.org/v2/mgo/bson"
)

type Person struct {
    Name string
    Phone string
}

func main() {
    session, err := mgo.Dial("server1.example.com,server2.example.com")
    if err != nil {
        panic(err)
    }
    defer session.Close()

    session.SetMode(mgo.Monotonic, true)

    c := session.DB("test").C("people")
    err = c.Insert(&Person{"Ale", "+55 53 8116 9639"},
        &Person{"Cla", "+55 53 8402 8510"})
    if err != nil {
        panic(err)
    }

    result := Person{}
    err = c.Find(bson.M{"name": "Ale"}).One(&result)
    if err != nil {
        panic(err)
    }

    fmt.Println("Phone:", result.Phone)
}

We can see that there is no big different to operate database between mgo and beedb, they are both based on struct, this is what Go style is.

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