Adding bulk data to mysql database - mysql

Question

I have a console program where the user scans in serial numbers, and those serial numbers get added to a database.
const mysql = require('mysql2');
const read = require('readline-sync');
const conn = new mysql.createConnection(config);
conn.connect(
function(err){
if(err){
throw err;
}
else{
console.log("Connection Established");
while(1){
var sn = read.question('Scan in serial number: ');
conn.query('INSERT INTO test (serial) VALUES (?);',
[sn], function(err, results, fields){
if (err){
throw err;
}
else{
console.log("Added stuff");
}
});
}
}
}
);
When the code runs it successfully connects to the database but queries the database. It continually prompts for user input.
Alternatively, I tried storing serial numbers in an array and then loops through it adding each element, like this.
const mysql = require('mysql2');
const read = require('readline-sync');
var array = [];
var sn = " ";
while (1) {
sn = read.question('Scan in serial number, or enter "done" if finished scanning');
if (sn == "done") {
break;
}
array.push(sn);
}
conn.connect(
function (err) {
if (err) {
throw err;
}
else {
console.log("Connection Established");
array.forEach(function (sn) {
conn.query('INSERT INTO test (serial) VALUES (?);',
[sn], function (err, results, fields) {
if (err) {
throw err;
}
else {
console.log("Added stuff");
}
});
});
}
}
);
In this case, it works inconsistently. Sometimes it works fine, and other times it fails to connect and throws a timeout error. Is there a better way to accomplish this and/or am I doing something wrong?

Answer 1

var promises = []
function dbOp(value) {
return new Promise(function(resolve, reject) {
conn.query('INSERT INTO test (serial) VALUES (?);',
[value], function (err, results, fields) {
if (err) {
return reject(err)
}
else {
console.log("Added stuff");
resolve(results)
}
}
}
conn.connect(function(err){
if(err){
throw err;
}
else{
for (i = 0; i < array.length; ++i) {
promises.push(dbOp(array[i]));
}
}
});
Promise.all(promises)
.then((results) => {
console.log("done", results);
})
.catch((e) => {
console.log(e)
});

Answer 2

This might be caused by short idle timeout setting in your mysql server. client.connect() is pretty much a no-op in mysql2, it connects immediately when you call mysql.createConnection(). You can change order to establish connection only after all data is collected:
const mysql = require('mysql2');
const read = require('readline-sync');
var array = [];
var sn = ' ';
while (1) {
sn = read.question('Scan in serial number, or enter "done" if finished scanning');
if (sn == 'done') {
const conn = mysql.createConnection(config);
array.forEach(function(sn) {
conn.query('INSERT INTO test (serial) VALUES (?);', [sn], function(err, results, fields) {
if (err) {
throw err;
} else {
console.log('Added stuff');
}
});
});
}
array.push(sn);
}