Re: Strange behavior of transcations

On Sunday, June 5, 2022, Hui Jackson <jackhts4@gmail.com> wrote:

I am working on node-postgres and there is a strange transactions.

The function aims at locking user's wallet until the refund process is complete, then will update item's has_refund to true.
The problem I am facing is the program return no error, but the database is not updated. Unless I spam the function for multiple times then the value is updated.
If I remove begin and commit, then the function work perfectly.

const refundService = (itemId) =>{

    await pgPool.query('BEGIN;');

    const users = (await pgPool.query('SELECT * from app_user where $1=ANY(purchase_list);', [ itemId ])).rows;

    for(let i = 0; i < users.length; i++){

        refund(users[i])

    }

    await pgPool.query('UPDATE item_lists SET has_refund = $1 where id = $2;', [true,  itemId ]);

    await pgPool.query('COMMIT;');

}

   

const refund = (user) =>{

    const refund = 10

    await pgPool.query('UPDATE app_user SET wallet = wallet + $1', [refund ]);

}

I think you are mis-using your pool.  If you want transactions you need checkout a connection from the pool and use it for every command in the transaction.  The one-shot query method on the pool is meant for standalone commands.  I say think because I’m unsure why you’d get no updates instead of updates but no transaction…

David J.