The select eventid, r_eventid from event_recovery order by r_eventid, eventid desc query (patch #3030030) may cause an issue during Zabbix DB upgrade.

Steps to reproduce:

1. Set up CentOS or Debian server with (512MB - 1GB RAM)
2. Don't enable swap (or disable it)
3. Create DB for Zabbix 3.2
4. Generate problems to increase "event_recovery" table size to 1-2GB
5. Start upgrade to 3.4 version

Result CentOS 7:
The "select eventid, r_eventid from event_recovery order by r_eventid, eventid desc" query will cause recurring "Out Of Memory" events for MySQL. At some point, the server may stack at all (if oom-killer score was adjusted for MySQL).

Result Debian 8:
The upgrade is running... forever? No visible issues from Zabbix server or MySQL side.
At the same time, Zabbix will stack at "3030030" patch and will continuously run "select eventid, r_eventid from event_recovery order by r_eventid, eventid desc" query. You will see "can't allocate enough memory" error on inspection with "strace".

Expected:
Zabbix should add database upgrade failed error to log (with details about issue) and stop upgrade after several attempts if server has no enough memory.