Hello,
I use a PG database on a HPC system (cluster). My processes get a dataset from the database and change the row, each
processis independend.
My table shows something like: id, status, data
id = PK a unqiue number
status a enum value which "open", "waiting", "working", "done"
So each process calls a SQL statement select * from where status = "waiting", so the process should get the next
waitingtask, after the process
gets the task, the status should be changed to "working", so no other process shouldn't get the task. My processes are
independed,so it can
be, that 2 (or more) processes call the select statement at the same time and get in this case equal tasks, so I need
somelocking. How can
I do this with Postgres, that each row / task in my table is read / write by one process. On threads I would create a
mutexeg:
lock()
row = select * from table where status = waiting
update status = working from table where id = row.id
unlock()
do something with row
Which is the best solution with postgres? should I create a procedure which takes the next job, change it and returns
theid, so each process
calls "select getNextJob()" ?
Thanks
Phil