SQL query with async each - sql

Question

My problem is when I am getting array of users and trying to run async each it start each sqlRequest and not going one by one pushing in array.
It should do sqlRequest 1 by 1, and not do all by each user sqlRequest and the push in an array.
Here is a async each
function getUserFavCat(params, callback) {
var usersArrayCat = [];
async.each(params, function (user, cb) {
sqlRequest("SELECT b_cat.title, b_cat.id FROM dbo.Students st INNER JOIN dbo.SaleView sv ON sv.userId = st.id INNER JOIN dbo.KEY_BrandcategoryToSale b_key ON b_key.saleId = sv.saleId INNER JOIN dbo.BrandCategories b_cat ON b_cat.id = b_key.brandCategoryId WHERE st.id = " + user.id, function (err, result) {
if (!result) {
//console.error("NO FAVOURITE CATEGORY FOR USER " + JSON.stringify(user))
} else if (result.length == 0) {
//console.error("NO FAVOURITE CATEGORY FOR USER " + JSON.stringify(user))
} else {
user.favouriteCat = utils.takeMostRepeatingObj(result);
usersArrayCat.push(user);
}
cb();
})
}, function() {
callback(null, usersArrayCat)
});
};
Here is the SQL query:
function sqlRequest (sqlQuery, callback) {
var connection = new sql.Connection(sql_conf, function (err) {
if (err){
console.log(err)
} else {
var request = new sql.Request(connection);
request.query(sqlQuery, function(err, result) {
console.log(result)
if(err){
console.error(err)
} else if(!result){
console.error("NO RESPONSE SQL QUERY")
} else {
callback(null, result);
connection.close();
}
})
}
});
connection.on('error', function(err) {
console.log(err);
});
};

Answer 1

use async.eachLimit to limit the no. of request
function getUserFavCat(params, callback) {
var usersArrayCat = [];
console.log(`length of array ${params.length}`)
// 1 here means 1 request at a time
async.eachLimit(params, 1, function (user, cb) {
sqlRequest("SELECT b_cat.title, b_cat.id FROM dbo.Students st INNER JOIN dbo.SaleView sv ON sv.userId = st.id INNER JOIN dbo.KEY_BrandcategoryToSale b_key ON b_key.saleId = sv.saleId INNER JOIN dbo.BrandCategories b_cat ON b_cat.id = b_key.brandCategoryId WHERE st.id = " + user.id, function (err, result) {
if (!result) {
//console.error("NO FAVOURITE CATEGORY FOR USER " + JSON.stringify(user))
} else if (result.length == 0) {
//console.error("NO FAVOURITE CATEGORY FOR USER " + JSON.stringify(user))
} else {
user.favouriteCat = utils.takeMostRepeatingObj(result);
usersArrayCat.push(user);
cb();
}
})
}, function (err) {
if (err) return callback(err);
callback(null, usersArrayCat)
});
};

Answer 2

Try this trick by using async.map and push for every callback to an array. Then you can use async.parallel to filter out the callback results for the success user and push it to usersArrayCat arrays
function getUserFavCat(params, callback) {
var usersArrayCat = [], callbackArrays = [];
async.map(params, function (user, cb) {
callbackArrays.push(function (cb) {
sqlRequest("SELECT b_cat.title, b_cat.id FROM dbo.Students st INNER JOIN dbo.SaleView sv ON sv.userId = st.id INNER JOIN dbo.KEY_BrandcategoryToSale b_key ON b_key.saleId = sv.saleId INNER JOIN dbo.BrandCategories b_cat ON b_cat.id = b_key.brandCategoryId WHERE st.id = " + user.id, function (err, result) {
if (!result) {
user.status = '99'; // error status
cb(null, user);
} else if (result.length == 0) {
user.status = '99'; // error status
cb(null, user);
} else {
user.favouriteCat = utils.takeMostRepeatingObj(result);
user.status = '00'; //success status
cb(null, user);
}
});
}, function(err, results) {
// comes here after all individual async calls have completed
// check errors; array of results is in data
cb(null, results)
});
async.parallel(callbackArrays, function (err, results) {
results.forEach (function (elem, ind) {
if (elem.status == '00') {
usersArrayCat.push(elem);
}
});
});
};