Node JS for loop and database query - mysql

Question

I'm running a for loop on a function, and the database is updated on each loop. It then calls the database again using the for loop to update values on the database. However it seems to appear like i'm getting cached results. Is there any reason for this error?
I can post my code, but it's kind of tedious.
It's a simple for loop on a module function that calls a database request, then updates that database.
module.exports.newElectronicHyperCredit = function(request){
gt = request.body.custom + "-" + Date.now()
db.query(
"SELECT * FROM Tenderizer.Stats ORDER BY ID DESC LIMIT 1",
[
],
function(error, stats){
bsr = stats[0]['BuySellRate'];
dv = stats[0]['DollarValue'];
credits = stats[0]['Credits'];
for(i = 0; i < request.body.quantity; i++){
bsr = dv / credits;
dv = Number(dv) + 10;
credits = Number(credits) + (7 / BSR);
denomination = 7 / bsr;
db.query(
"INSERT INTO Tenderizer.Stats SET ?",
{
BuySellRate: bsr,
DollarValue: dv,
Credits: credits
},
function(error, stats){
}
)
db.query(
"SELECT * FROM Tenderizer.Withdrawals ORDER BY case when Withdrawals.Owner = 'Rah1337' then 1 else 2 end, Withdrawals.ID DESC",
[
],
function(error, withdrawals){
withdrawn = 0;
for(x in withdrawals){
if(denomination != 0){
if(withdrawals[x]['Denomination'] > denomination){
withdrawn = withdrawn + denomination;
db.query(
"UPDATE Tenderizer.Withdrawals SET Denomination = Denomination - ? WHERE ID = ?",
[
denomination,
withdrawals[x]['ID']
],
function(error, points){
}
);
db.query(
"INSERT INTO Tenderizer.Points SET ?",
{
GenerationTag: withdrawals[x]['GenerationTag'],
Owner: request.body.custom,
Denomination: denomination,
BoughtPoint: bsr,
Since: Date.now()
},
function(error, points){
}
);
db.query(
"INSERT INTO Tenderizer.Payouts SET ?",
{
GenerationTag: withdrawals[x]['GenerationTag'],
Owner: withdrawals[x]['Owner'],
DollarValue: bsr * withdrawals[x]['Denomination'],
Denomination: denomination,
Processed: 0,
Since: Date.now()
},
function(error, payouts){
}
);
denomination = 0;
}else{
withdrawn = withdrawn + denomination;
db.query(
"DELETE FROM Tenderizer.Withdrawals WHERE ID = ?",
[
withdrawals[x]['ID']
],
function(error, withdrawals){
}
);
db.query(
"INSERT INTO Tenderizer.Points SET ?",
{
GenerationTag: withdrawals[x]['GenerationTag'],
Owner: request.body.custom,
Denomination: withdrawals[x]['Denomination'],
BoughtPoint: bsr,
Since: Date.now()
},
function(error, points){
}
);
db.query(
"INSERT INTO Tenderizer.Payouts SET ?",
{
GenerationTag: withdrawals[x]['GenerationTag'],
Owner: withdrawals[x]['Owner'],
DollarValue: bsr * withdrawals[x]['Denomination'],
Denomination: withdrawals[x]['Denomination'],
Processed: 0,
Since: Date.now()
},
function(error, payouts){
}
);
denomination = denomination - withdrawals[x]['Denomination'];
}
}
}
if(denomination > 0){
db.query(
"INSERT INTO Tenderizer.Pool SET ?",
{
GenerationTag: gt,
Username: request.body.custom,
DollarValue: 10 - (withdrawn * bsr),
Withdrawn: 0,
Since: Date.now()
},
function(error, pool){
}
);
db.query(
"INSERT INTO Tenderizer.Points SET ?",
{
GenerationTag: gt,
Owner: request.body.custom,
Denomination: denomination,
BoughtPoint: bsr,
Since: Date.now()
},
function(error, points){
}
);
}
db.query(
"UPDATE Tenderizer.EHC_Count SET Credits = Credits + ? WHERE Username = ?",
[
7 / bsr
],
function(error, ehc_count){
}
);
}
);
}
}
);
};
It's not inserting the records one by one, it's inserting it all at once or it's using cached results. Because the rows that i'm recieving in my database are
duplicate rows rather than incrementing rows. In the points table in the denomination column and the bought point.

Answer 1

You're using lots of callbacks, but you're not actually doing anything to wait until those callbacks are called. This is difficult to resolve using callbacks, but could be done much more easily if you use a library that supports Promises.
For example, this is what the code would look like if you properly await each query using #databases/mysql
const createConnectionPool = require('#databases/mysql');
const {sql} = require('#databases/mysql');
const db = createConnectionPool();
module.exports.newElectronicHyperCredit = async function(request){
let gt = request.body.custom + "-" + Date.now()
const stats = await db.query(
sql`SELECT * FROM Tenderizer.Stats ORDER BY ID DESC LIMIT 1`,
);
let bsr = stats[0]['BuySellRate'];
let dv = stats[0]['DollarValue'];
let credits = stats[0]['Credits'];
for(let i = 0; i < request.body.quantity; i++){
bsr = dv / credits;
dv = Number(dv) + 10;
credits = Number(credits) + (7 / BSR);
denomination = 7 / bsr;
await db.query(sql`
INSERT INTO Tenderizer.Stats (BuySellRate, DollarValue, Credits)
VALUES (${bsr}, ${dv}, ${credits}
`)
const withdrawals = await db.query(sql`
SELECT * FROM Tenderizer.Withdrawals
ORDER BY case when Withdrawals.Owner = 'Rah1337' then 1 else 2 end, Withdrawals.ID DESC
`)
withdrawn = 0;
for(x in withdrawals){
if(denomination != 0){
if(withdrawals[x]['Denomination'] > denomination){
withdrawn = withdrawn + denomination;
await db.query(sql`
UPDATE Tenderizer.Withdrawals
SET Denomination = Denomination - ${denomination}
WHERE ID = ${withdrawals[x]['ID']}
`);
await db.query(sql`
INSERT INTO Tenderizer.Points (GenerationTag, Owner, Denomination, BoughtPoint, Since)
VALUES (
${withdrawals[x]['GenerationTag']},
${request.body.custom},
${denomination},
${bsr},
${Date.now()}
)
`);
await db.query(sql`
INSERT INTO Tenderizer.Payouts (GenerationTag, Owner, DollarValue, Denomination, Processed, Since)
VALUES (
${withdrawals[x]['GenerationTag']},
${withdrawals[x]['Owner']},
${bsr * withdrawals[x]['Denomination']},
${denomination},
${0},
${Date.now()}
)
`);
denomination = 0;
}else{
withdrawn = withdrawn + denomination;
await db.query(
sql`DELETE FROM Tenderizer.Withdrawals WHERE ID = ${withdrawals[x]['ID']}`
);
await db.query(sql`
INSERT INTO Tenderizer.Points (GenerationTag, Owner, Denomination, BoughtPoint, Since)
VALUES (
${withdrawals[x]['GenerationTag']},
${request.body.custom},
${withdrawals[x]['Denomination']},
${bsr},
${Date.now()}
)
`);
await db.query(sql`
INSERT INTO Tenderizer.Payouts (GenerationTag, Owner, DollarValue, Denomination, Processed, Since)
VALUES (
${withdrawals[x]['GenerationTag']},
${withdrawals[x]['Owner']},
${bsr * withdrawals[x]['Denomination']},
${withdrawals[x]['Denomination']},
${0},
${Date.now()}
)
`);
denomination = denomination - withdrawals[x]['Denomination'];
}
}
}
if(denomination > 0){
await db.query(sql`
INSERT INTO Tenderizer.Pool (GenerationTag, Username, DollarValue, Withdrawn, Since)
VALUES (
${gt},
${request.body.custom},
${10 - (withdrawn * bsr)},
${0},
${Date.now()}
)
`);
await db.query(sql`
INSERT INTO Tenderizer.Points (GenerationTag, Owner, Denomination, BoughtPoint, Since)
VALUES (
${gt},
${request.body.custom},
${denomination},
${bsr},
${Date.now()}
)
`);
}
await db.query(sql`UPDATE Tenderizer.EHC_Count SET Credits = Credits + ${7 / bsr} WHERE Username = ${request.body.custom}`)
}
};
P.S. it also looks like you're forgetting to actually declare your variables (using let or const before you assign values to them.
P.P.S doing all these queries in a loop may be quite slow, because each one will be executed sequentially. This will be necessary if each query depends on the result of the previous one, but if that's not the case, you could replace one/all of the loops with await Promise.all(list.map(async (value, index) => {...})), which will run the function for each value in the list, but will run it in parallel.