const async = require('async');
const mysql = require('mysql');
const select = 'SELECT `strkey`, `strvalue` FROM `store` WHERE `strkey` = ? AND `strvalue` = ?';
const insert = 'INSERT INTO `store` (`strkey`, `strvalue`) VALUES (?, ?)';

const connection = mysql.createConnection({
    host: 'localhost',
    user: 'root',
    password: 'root',
    database: 'async_node_test'
});

var data = [
    {key: 'key1', value: 'key1'},
    {key: 'key2', value: 'key2'},
    {key: 'key3', value: 'key3'},
    {key: 'key4', value: 'key4'},
    {key: 'key5', value: 'key5'}
];

var func = function(callback) {
    console.log(this);
    var key = this.key;
    var value = this.value;

    connection.query(select, [key, value], function(err, results, fields) {
        if( results.length > 0) {
            callback(null, 'already');
            return;
        }
        connection.query(insert, [key ,value], function(err, results) {
            console.log(err);
            callback(null, 'success');
        })
    });
};

var functions = [];
for(var i = 0; i < data.length; i++) {
    functions.push(func.bind(data[i]));
}

connection.connect();
async.parallel(functions, function(err, results) {
    connection.end(function() {
        console.log('connection close');
        console.log(results);
        console.log(err);
    });
});