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.