I was looking for some help in regards to a database package that I'm building for a larger application. The application will essentially keep certain information on a database through the use of the mysql package in npm. The problem I'm facing is that when I try to pass the results variable to a variable that I've created I always get undefined. Though if I place a log statement underneath the variable transfer statement displaying the results variable it will be properly populated. I've done a fair amount of research and believe that this has something to do with promises and/or the callback function that's part of the query. I was wondering if I could have someone examine my code and let me know the best course of action. I've spent a couple of hours on this researching online and trying various solutions but nothing has worked.
const mysql = require("mysql");
var sqlResults;
var pool = mysql.createPool({
host: "example.com",
user: "exampleUser",
password: "123456Password",
database: "TestDB"
});
module.exports = {
...
databaseSelect: function(table, fields, conditionalStmt) {
pool.getConnection(function(err, connection) {
if (err)
throw err;
console.log("Connected to the example DB!");
var sql = "SELECT " + fields + " FROM " + table + " " + conditionalStmt;
connection.query(sql, function(error, results, fields) {
console.log("Successfully retrieved records from " + table + "\n\t" + sql);
sqlResults = results;
connection.release();
sqlResults = results;
console.log(results);
if (error)
throw error;
});
});
console.log(sqlResults);
return sqlResults;
}
}
Here's a sample of the output that I'm receiving:
I am ready!
undefined
undefined
Connected to the example DB!
Successfully retrieved records from User_Level_Info
SELECT HashID, Level, Experience FROM User_Level_Info WHERE HashID = 'e578059cabc6f937f0219127384126143e272acbac52c331345d573e0f085d21'
[ RowDataPacket {
HashID: 'e578059cabc6f937f0219127384126143e272acbac52c331345d573e0f085d21',
Level: 1,
Experience: 0 } ]
Here convert it into a Promise.
So this will wait until it gets resolved or reject
databaseSelect: function(table, fields, conditionalStmt) {
return new Promise(function(resolve, reject) {
pool.getConnection(function(err, connection) {
if (err)
return reject(err);
console.log("Connected to the example DB!");
var sql = "SELECT " + fields + " FROM " + table + " " + conditionalStmt;
connection.query(sql, function(error, results, fields) {
console.log("Successfully retrieved records from " + table + "\n\t" + sql);
sqlResults = results;
connection.release();
sqlResults = results;
console.log(results);
if (error)
return reject(error);
});
});
resolve(sqlResults);
});
}
//call your function
databaseSelect(params)
.then(function(rows) {
console.log(rows)
})
.catch((err) {
console.log(err)
}); // Throw async to escape the promise chain
My html code is
<form action="/file_upload" method="POST" enctype="multipart/form-data">
<input type="file" name="photos" id="photos" accept='image/*' multiple>
<input type="submit" value="Upload" id="upload_my_photos" disabled>
</form>
In sails I am using
uploadFiles = req.file("photos");
This is only fetching just single file.
Edit : I would also like to save the individual files. Below is the code I am using but no files are getting uploaded:
req.file('photos').upload(function (err, uploadedPhotos) {
if (err) return res.serverError(err);
async.eachSeries(uploadedPhotos,
function (uploadedFile, callback) {
sails.log("upload file size and name is " + uploadedFile.size + " " + uploadedFile.filename);
req.file(uploadedFile).upload({
dirname: "path/to/directory",
// saveAs: function (file, cb) { cb(null, file.filename); }
},
function onUploadComplete(err, files) {
if (err) return res.serverError(err);
if (files.length === 0) {
return res.badRequest('No file was uploaded');
}
sails.log("files uploaded");
});
}, function (err) {
// if any of the saves produced an error, err would equal that error
if (err) {
console.log(err);
} else {
return res.status(200).send({ success: false, message: "failed to upload" });
}
});
});
Sails req.file() is representing an incoming multipart file upload from the specified field.
You need to subscribe to the request with a callback in which the uploaded files will be passed as an second argument:
req.file('photos').upload(function (err, uploadedPhotos){
if (err) return res.serverError(err);
return res.json({
message: uploadedPhotos.length + ' file(s) uploaded successfully!',
files: uploadedPhotos
});
});
I have a method getconnection() that creates connection for me.
Here's the function.
I get undefined even if I am fetching result of query that is rows to callback function to send the response to controller.
Can someone help me out.Thanks in advance.
function fetchUserInfo(req,res)
{
var getUserInfo = "select First_Name, Last_Name,COUNT(*) FROM twitter.user_information INNER join twitter.tweets ON user_information.Twitter_Handle = tweets.Twitter_handle WHERE user_information.Twitter_Handle = '"+req.session.handle+"' ";
console.log("Fetch User-------------"+getUserInfo);
mysql.fetchUser(function(err,result){
if(err)
{ console.log("cannot be retrieved");
throw err;
}
else
{
console.log("Successfully retrieved");
console.log("---------------" + result);
console.log(result.First_Name);
res.send(result);
}
},getUserInfo);
}
// mysql function
function fetchUser(callback,sqlQuery)
{
console.log("In fetch Data");
console.log("SQLquery is:::"+sqlQuery);
connection.getConnection().query(sqlQuery, function(err,rows,fields){
if(err)
{
console.log("Error :"+err.message);
}
else
{
console.log("Result is :" + rows.First_Name);
callback(err, rows);
}
})
}
Try this:
console.log("Result is :" + rows[0].First_Name);
or try to print the rows variable to the console instead of rows.First_Name:
console.log(rows);
here i need to convert my excel to json,since i have been in the right path file only.While running it shows a following error:
[TypeError: Cannot set property length of [object Object] which has only a getter]Any help?
node_x = require("xls-to-json");
var stack = new Error().stack;
try{
node_x({
input: "Book1.xls", // input xls
output: "output.json" // output json
}, function(err, result) {
if(err) {
console.error(err);
} else {
console.log(result);
}
});
}catch(e){
console.log("ssfffs");
console.error(e);
}
Try entering the sheet name as well
node_xj = require("xls-to-json");
node_xj({
input: "Book1.xls", // input xls
output: "output.json", // output json
sheet: "sheetname" // specific sheetname
}, function(err, result) {
if(err) {
console.error(err);
} else {
console.log(result);
}
});
Can anyone provide an example of how I could achieve MySQL transactions in Node.js. I am trying to get my head around using the node-mysql driver and node-mysql-queue.
As far are I can tell, using node-mysql-queue greatly reduces the asynchronous nature of Node.js as new queries have to wait until existing ones have completed. To get around this, has anyone attempted to combine node-mysql-queue with node-mysql's connection-pooling capabilities. i.e starting a new mysql connection for each new http request, and starting transaction queues on individual connections?
Update
See the edit below for async/await syntax
I spent some time writing a generalized version of the transaction example given by node mysql, so I thought I would share it here. I am using Bluebird as my promise library, and used it to 'promisify' the connection object which simplified the asynchronous logic a lot.
const Promise = ('bluebird');
const mysql = ('mysql');
/**
* Run multiple queries on the database using a transaction. A list of SQL queries
* should be provided, along with a list of values to inject into the queries.
* #param {array} queries An array of mysql queries. These can contain `?`s
* which will be replaced with values in `queryValues`.
* #param {array} queryValues An array of arrays that is the same length as `queries`.
* Each array in `queryValues` should contain values to
* replace the `?`s in the corresponding query in `queries`.
* If a query has no `?`s, an empty array should be provided.
* #return {Promise} A Promise that is fulfilled with an array of the
* results of the passed in queries. The results in the
* returned array are at respective positions to the
* provided queries.
*/
function transaction(queries, queryValues) {
if (queries.length !== queryValues.length) {
return Promise.reject(
'Number of provided queries did not match the number of provided query values arrays'
)
}
const connection = mysql.createConnection(databaseConfigs);
Promise.promisifyAll(connection);
return connection.connectAsync()
.then(connection.beginTransactionAsync())
.then(() => {
const queryPromises = [];
queries.forEach((query, index) => {
queryPromises.push(connection.queryAsync(query, queryValues[index]));
});
return Promise.all(queryPromises);
})
.then(results => {
return connection.commitAsync()
.then(connection.endAsync())
.then(() => {
return results;
});
})
.catch(err => {
return connection.rollbackAsync()
.then(connection.endAsync())
.then(() => {
return Promise.reject(err);
});
});
}
If you wanted to use pooling as you suggested in the question, you could easily switch the createConnection line with myPool.getConnection(...), and switch the connection.end lines with connection.release().
Edit
I made another iteration of the code using the mysql2 library (same api as mysql but with promise support) and the new async/await operators. Here is that
const mysql = require('mysql2/promise')
/** See documentation from original answer */
async function transaction(queries, queryValues) {
if (queries.length !== queryValues.length) {
return Promise.reject(
'Number of provided queries did not match the number of provided query values arrays'
)
}
const connection = await mysql.createConnection(databaseConfigs)
try {
await connection.beginTransaction()
const queryPromises = []
queries.forEach((query, index) => {
queryPromises.push(connection.query(query, queryValues[index]))
})
const results = await Promise.all(queryPromises)
await connection.commit()
await connection.end()
return results
} catch (err) {
await connection.rollback()
await connection.end()
return Promise.reject(err)
}
}
The following transaction example was added to the documentation a month ago:
https://github.com/felixge/node-mysql#transactions
connection.beginTransaction(function(err) {
if (err) { throw err; }
connection.query('INSERT INTO posts SET title=?', title, function(err, result) {
if (err) {
connection.rollback(function() {
throw err;
});
}
var log = 'Post ' + result.insertId + ' added';
connection.query('INSERT INTO log SET data=?', log, function(err, result) {
if (err) {
connection.rollback(function() {
throw err;
});
}
connection.commit(function(err) {
if (err) {
connection.rollback(function() {
throw err;
});
}
console.log('success!');
});
});
});
});
I am using the following approach. There is an add function in my Model where I am performing database operations.
add : function (data, callback) {
//Begin transaction
connection.beginTransaction(function(err) {
if (err) {
throw err;
}
var user_query = "INSERT INTO `calldata`.`users` (`username`, `password`, `enabled`, `accountNonExpired`, `accountNonLocked`, `credentialsNonExpired`) VALUES ('" + data.mobile + "', '" + sha1(data.password) + "', '1', '1', '1', '1')";
connection.query(user_query, function(err, results) {
if (err) {
return connection.rollback(function() {
throw err;
});
}
var accnt_dtls_query = "INSERT INTO `calldata`.`accnt_dtls` (`req_mob_nmbr`, `usr_nme`, `dvce_id`, `mngr_id`, `cmpny_id`, `actve_flg`, `crtd_on`, `usr`) VALUES (" + data.mobile + ", '" + data.name + "', '', " + data.managerId + ", " + data.companyId + ", 1, now(), '" + data.mobile+ "')";
connection.query(accnt_dtls_query, function(err, results) {
if (err) {
return connection.rollback(function() {
throw err;
});
}
var user_role_query = "INSERT INTO `calldata`.`user_roles` (`username`, `ROLE`) VALUES ('" + data.mobile + "', '" + data.role + "')";
connection.query(user_role_query, function(err, result) {
if (err) {
return connection.rollback(function() {
throw err;
});
}
//add an entry to manager table
var mngr_dtls_query = "INSERT INTO `calldata`.`mngr_dtls` (`mngr_nm`, `cmpny_id`, `crtd_on`, `usr_nm`, `eml_id`) VALUES ('" + data.name + "'," + data.companyId + " , now(), '" + data.mobile + "', '" + data.mobile + "')";
connection.query(mngr_dtls_query, function(err, result) {
if (err) {
return connection.rollback(function () {
throw err;
});
}
console.log('Changed ' + result.changedRows + ' results');
connection.commit(function (err) {
console.log('Commiting transaction.....');
if (err) {
return connection.rollback(function () {
throw err;
});
}
console.log('Transaction Complete.');
connection.end();
callback(null, result);
});
});
});
});
});
});
//transaction ends here
}
and calling from controller:
agentAccountModel.add(data, function(err, results) {
if(err)
{
res.status(500);
res.json({
"status": 500,
"message": err
});
}
res.status(200);
res.json({
"status": 200,
"message": "Saved successfully"
});
});
I have come up with a solution using a recursive function.
var sql = 'INSERT INTO logs SET data = ?';
// array of rows to insert
var rows = [[/*first row*/], [/*additional row*/]];
connection.beginTransaction(function (err) {
if (err) {
throw err;
}
var insertEachRow = function () {
var row = rows.shift();
if (! row) {
// Done, now commit
return noMoreRows();
}
connection.query(sql, row, function (err, result) {
if (err) {
connection.rollback(function () {
throw err;
});
}
insertEachRow();
});
};
var noMoreRows = function () {
connection.commit(function (err) {
if (err) {
connection.rollback(function () {
throw err;
});
}
console.log('success!');
});
};
insertEachRow();
});
I found one useful links which uses node js mysql pooling with transaction. Database Connection pooling is always useful. One can check this link
https://github.com/mysqljs/mysql
I created a wrapper ORM type thing for this specific purpose, hope it helps SQl-connecton - pool ORM type helper methods
You can use it with the mysql also, just use this function without any parameters /call back .
Make sure you have async function and use these instead
await con.rollback();
await con.beginTransaction();
await con.commit();
Life set.....