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Re: Using Transaction with if-else in prepared statement - Mailing list pgsql-sql

From Steve Midgley
Subject Re: Using Transaction with if-else in prepared statement
Date
Msg-id CAJexoS+Xa2A1QN2BSmBKSqbKC5Yhs=K7RHqsniKonQMuFt14LA@mail.gmail.com
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In response to Using Transaction with if-else in prepared statement  (Hui Jackson <jackhts4@gmail.com>)
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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);
 

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