store mysql query results in redis - mysql

Question

I am trying to use redis to store a list of users and weather or not they are online or offline and displaying that information to other users.
I am fairly new to node and I believe that I need to use either a list or sorted sets.
when it gets to the console.log(reply); line it only shows "Object"
I think I need to loop through the results of the query to build the list but I am not really sure 1) how to loop through the results directly in the server application and 2) how to build the list or sorted set based on that query.
Any advice or suggestions would be greatly appreciated.
var mysql = require('mysql');
var connection = mysql.createConnection({
host : 'localhost',
user : 'root',
password : 'password',
database : 'users'
});
var redis = require('redis')
, client = redis.createClient();
connection.connect();
connection.query('SELECT * FROM user_profile', function(err, rows, fields)
{
if (err) throw err;
client.set('string key', rows[0], redis.print);
client.get("string key", function (err, reply) {
console.log(reply);
});
});
connection.end();

Answer 1

1) I assume rows contains an array of objects, each object representing a user data record.
client.set('string key', rows[0], redis.print);
is storing the whole first object of rows array, you can use a foreach statement to loop over all values returned.
You are saving the whole object in redis, but you only need the online/offline state 1 or 0. Besides, you can store only strings in redis keys (see Redis Keys Docs and Redis Set Docs)
2) You don't need a list or sorted sets only for online/offline state of a user, unless you need some sorting operations later.
You can use simple keys, I suggest using a pattern like this for key name: "user:".
// assuming that user_name property exists, holds username data "david" and it's unique
client.set("user:"+row[0].user_name, 0, redis.print); // stores key "user:david" = "0";`
Then to retrieve it use:
client.get("user:"+row[0].user_name);
So, your sql query callback function could look like this:
function(err, rows, fields) {
if (err) throw err;
rows.forEach(function(element, index, array){
client.set('user:'+element.user_name, 0, redis.print);
client.get("user:"+element.user_name, function (err, reply) {
console.log(reply);
});
});
}
Please note that the user name must be unique. You can use user ID's if not