Job control in sql

Hi. <br /><br /> I am building a system, where we have jobs that run at different times (and takes widely different
lengthsof time). <br /><br /> Basically I have a jobs table: <br /><br /> create table jobs(<br />      id serial, <br
/>    ready boolean, <br />     job_begun timestamptz, <br />     job_done timestamptz, <br />     primary key (id)<br
/>);<br /><br /> This should run by cron, at it is my intention that the cronjob (basically) consists of<br /><i><br />
psql-c "select run_jobs()"</i><br /><br /> My problem is, that the job should ensure that it is not running already,
whichwould be to set job_begun when the job starts". That can easily happen as jobs should be started every 15 minutes
(tolower latency from ready to done) but some jobs can run for hours.. <br /><br /> The problem is that a later run of
run_jobs()will not see the job_begun has been set by a prior run (that is unfinished - as all queries from the
plpgsql-functionruns in a single, huge transaction). <br /><br /> My intitial idea was to set the isolation level to
"readuncommitted" while doing the is-somebody-else-running-lookup, but I cannot change that in the plpgsql function (it
complainsthat the session has to be empty - even when I have run nothing before it). <br /><br /> Any ideas on how to
solvethe issue?<br /><br /> I run it on Pgsql 9.1.<br /><br /> Svenne<br />