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Thread: Using Transaction with if-else in prepared statement

Using Transaction with if-else in prepared statement

From
Hui Jackson
Date:
I am trying to make transaction in nodejs
The logic will be check if sufficient coin in sender's amount, if sufficient then do transaction.
I am new to postgres, not sure if this is a right way to do so, if you have a better solution, please let me know, thank you.

const coin = 10
const senderId = 1
const receiverId = 2
await pgPool.query(`
DO $$
    BEGIN
        if (SELECT coin from app_user where id = $1) >= $3 THEN
            UPDATE app_user set coin = coin - $3 where id = $1;
            UPDATE app_user set coin = coin + $3 where id = $2;
            INSERT INTO coin_history(sender_id, receiver_id, amount) VALUES ($1, $2, $3)

        END IF;
    END;
$$`,[senderId, receiverId, coin]);

Error (node:10044) UnhandledPromiseRejectionWarning: error: bind message supplies 3 parameters, but prepared statement "" requires 0

Re: Using Transaction with if-else in prepared statement

From
Steve Midgley
Date:


On Wed, May 25, 2022 at 4:13 AM Hui Jackson <jackhts4@gmail.com> wrote:
I am trying to make transaction in nodejs
The logic will be check if sufficient coin in sender's amount, if sufficient then do transaction.
I am new to postgres, not sure if this is a right way to do so, if you have a better solution, please let me know, thank you.

const coin = 10
const senderId = 1
const receiverId = 2
await pgPool.query(`
DO $$
    BEGIN
        if (SELECT coin from app_user where id = $1) >= $3 THEN
            UPDATE app_user set coin = coin - $3 where id = $1;
            UPDATE app_user set coin = coin + $3 where id = $2;
            INSERT INTO coin_history(sender_id, receiver_id, amount) VALUES ($1, $2, $3)

        END IF;
    END;
$$`,[senderId, receiverId, coin]);

Error (node:10044) UnhandledPromiseRejectionWarning: error: bind message supplies 3 parameters, but prepared statement "" requires 0

For debugging, you might try to sending each select, update, and insert in separate NodeJS query statements. You can do the IF work in NodeJS via a select for data from Pg.

But at the core of your problem I believe is that you are not configuring the postgres statement to receive parameters, but your injecting parameters from Node. From the Pg docs on prepared statements: https://www.postgresql.org/docs/current/sql-prepare.html

PREPARE fooplan (int, text, bool, numeric) AS
    INSERT INTO foo VALUES($1, $2, $3, $4);
EXECUTE fooplan(1, 'Hunter Valley', 't', 200.00);
 

Re: Using Transaction with if-else in prepared statement

From
hubert depesz lubaczewski
Date:
On Wed, May 25, 2022 at 07:12:49PM +0800, Hui Jackson wrote:
> I am trying to make transaction in nodejs
> The logic will be check if sufficient coin in sender's amount, if
> sufficient then do transaction.
> I am new to postgres, not sure if this is a right way to do so, if you have
> a better solution, please let me know, thank you.

I would do i by issuing *only*
INSERT INTO coin_history(sender_id, receiver_id, amount) VALUES
and then changing coin data with triggers plus adding constraints that
app_user.coin can never be < 0.

depesz

Re: Using Transaction with if-else in prepared statement

From
Hui Jackson
Date:
Concluded both methods shared:
1.  one query per each call for using prepared statement
await pgPool.query('BEGIN;');
const sender = (await pgPool.query('SELECT coin from app_user where id = $1;',[senderId])).rows[0];
if(sender.coin >= amount){
  await pgPool.query('UPDATE app_user set coin = coin - $1 where id = $2;',[coin, senderId]);
  await pgPool.query('UPDATE app_user set coin = coin + $1 where id = $2;',[coin, receiverId]);
  await pgPool.query('INSERT INTO coin_history(sender_id, receiver_id, amount) VALUES ($1, $2, $3)',[senderId, receiverId, coin]);
  await pgPool.query('COMMIT;');
}else{
  await pgPool.query('END;');
}
2. Use constraint
CREATE TABLE app_user(    id integer,    coin numeric CHECK (coin >= 0)
);

hubert depesz lubaczewski <depesz@depesz.com> 於 2022年5月26日週四 上午7:35寫道：
On Wed, May 25, 2022 at 07:12:49PM +0800, Hui Jackson wrote:
> I am trying to make transaction in nodejs
> The logic will be check if sufficient coin in sender's amount, if
> sufficient then do transaction.
> I am new to postgres, not sure if this is a right way to do so, if you have
> a better solution, please let me know, thank you.

I would do i by issuing *only*
INSERT INTO coin_history(sender_id, receiver_id, amount) VALUES
and then changing coin data with triggers plus adding constraints that
app_user.coin can never be < 0.

depesz