Question

The relates to OpenNMS where I’m trying to write an automation in SQL. I have a system which sends events to a table every time the backup succeeds. I want to detect if the backup is overdue for any given node. So for example the (simplified) table looks like:

nodeid, eventid, eventuei, eventtime
  1   ,  1     , backupOk, 09:20 15/12/09
  2   ,  2     , backupOk, 09:25 15/12/09
  3   ,  3     , backupOk, 09:30 15/12/09
  1   ,  4     , backupOk, 09:20 16/12/09
  2   ,  5     , backupOk, 09:25 16/12/09
  2   ,  6     , backupOk, 09:25 17/12/09
  3   ,  7     , backupOk, 09:30 17/12/09

So what I need is a list of nodeid’s where the backup is overdue by 24 hours (and I guess where no backup has occurred at all, although there are nodes in this database that don’t get backed up (as they are different types of node)).

Answer 1

Getting list of nodes that were not backed up – from your schema that you showed us – is not possible.

Getting list of nodes that are 24 hours overdue is trivial:

select nodeid, max(eventtime)
from your_table
group by nodeid
having max(eventtime) < now() - '24 hours'::interval