On Fri, Apr 8, 2022 at 2:26 PM Laurenz Albe <laurenz.albe@xxxxxxxxxxx> wrote:
On Thu, 2022-04-07 at 16:16 +0300, Andrus wrote:
> Orders are in table
>
> create table order (
> dokumnr int primary key,
> packno char(10)
> );
> insert into order dokumnr values (123);
>
> One user sets pack number using
>
> update order set packno='Pack1' where dokumnr=123
>
> 3 seconds later other user retrieves pack number using
>
> select packno from order where dokumnr=123
>
> However, other user gets null value, not Pack1 as expected. After some time later, correct value Pack1 is returned.
>
> How to get updated data from other user immediately?
> 3 seconds is long time, it is expected that select suld retrieve update data.
>
> There are lot of transactions running concurrently. Maybe update command is not written to database if second user retrieves it.
>
> How to flush orders table so that current results are returned for second user select ?
>
> Using
> PostgreSQL 13.2, compiled by Visual C++ build 1914, 64-bit
> and psqlODBC driver.
That cannot happen, unless
a) the UPDATE runs in a transaction that hasn't been committed
b) the SELECT is running on a standby server, and there is replication lag
There's also:
c) The SELECT runs in a transaction stat *started* before the transaction that a runs in. (Assuming it then retries with a new transaction later, that is)
