Bug #722: SELECT FOR UPDATE bug

Pablo Aviles
27/07/2002 10:58

To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
cc:
Subject: Re: [BUGS] Bug #722: SELECT FOR UPDATE bug

Hi,
we are use Postgresql 7.3.
The case in questions is: we have many clients (pc's) of postgresql. Every
client try to block an employee to display at user. The user make change
in the employee, but nobody can take the same employee at same time.
Before changes, the next step is update the record (Record blocked)

But, when I use
> SELECT * FROM employees
> WHERE status = 'A'
> LIMIT 1
> FOR UPDATE;
to catch the employee, only the first user select a record. Other users
can`t select any employee until the first user release the record. The
first conclusion here, is that Postgresql block all employee table.
When we try to use the LOCK sentence, the result don´t have change.

regards,
Pablo Avilés Cisneros
Technology, ITS
Software Development Area
Technology, ITS
San José, Costa Rica
email: paviles(at)its(dot)co(dot)cr

Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
27/07/2002 09:58

To: paviles(at)its(dot)co(dot)cr, pgsql-bugs(at)postgresql(dot)org
cc:
Subject: Re: [BUGS] Bug #722: SELECT FOR UPDATE bug

pgsql-bugs(at)postgresql(dot)org writes:
> SELECT * FROM employees
> WHERE status = 'A'
> LIMIT 1
> FOR UPDATE;

> The problem, in the previous sentence, is block every record on
> employees, although we want one record, we want limit 1.

I do not believe that. Could you give a more complete example of
your problem?

It would also help if you'd state which Postgres version you're using.

regards, tom lane