----- both groups do not have any access:


zabbix=> explain analyze             
SELECT   e.* FROM events e WHERE EXISTS (SELECT NULL FROM functions f,items i,hosts_groups hgg JOIN rights r ON r.id=hgg.groupid AND r.groupid IN ('11','15') WHERE e.objectid=f.triggerid AND f.itemid=i.itemid AND i.hostid=hgg.hostid GROUP BY f.triggerid HAVING MIN(r.permission)>0 AND MAX(r.permission)>='2') AND e.object='0' AND e.source='0' ORDER BY e.clock LIMIT 1 OFFSET 0;
                                                                                QUERY PLAN                                                                                
--------------------------------------------------------------------------------------------------------------------------------------------------------------------------
 Limit  (cost=0.28..18.24 rows=1 width=40) (actual time=35.057..35.057 rows=0 loops=1)
   ->  Index Scan using events_2 on events e  (cost=0.28..32748.20 rows=1824 width=40) (actual time=35.056..35.056 rows=0 loops=1)
         Index Cond: ((source = 0) AND (object = 0))
         Filter: (SubPlan 1)
         Rows Removed by Filter: 4286
         SubPlan 1
           ->  GroupAggregate  (cost=0.83..8.93 rows=1 width=12) (actual time=0.008..0.008 rows=0 loops=4286)
                 Group Key: f.triggerid
                 Filter: ((min(r.permission) > 0) AND (max(r.permission) >= 2))
                 ->  Nested Loop  (cost=0.83..8.91 rows=1 width=12) (actual time=0.007..0.007 rows=0 loops=4286)
                       ->  Nested Loop  (cost=0.70..8.72 rows=1 width=16) (actual time=0.003..0.006 rows=1 loops=4286)
                             ->  Nested Loop  (cost=0.56..8.57 rows=1 width=16) (actual time=0.002..0.004 rows=1 loops=4286)
                                   ->  Index Scan using functions_1 on functions f  (cost=0.28..4.28 rows=1 width=16) (actual time=0.001..0.001 rows=1 loops=4286)
                                         Index Cond: (e.objectid = triggerid)
                                   ->  Index Scan using items_pkey on items i  (cost=0.28..4.29 rows=1 width=16) (actual time=0.001..0.001 rows=1 loops=4901)
                                         Index Cond: (itemid = f.itemid)
                             ->  Index Only Scan using hosts_groups_1 on hosts_groups hgg  (cost=0.14..0.15 rows=1 width=16) (actual time=0.001..0.001 rows=1 loops=4901)
                                   Index Cond: (hostid = i.hostid)
                                   Heap Fetches: 0
                       ->  Index Scan using rights_2 on rights r  (cost=0.13..0.19 rows=1 width=12) (actual time=0.001..0.001 rows=0 loops=4909)
                             Index Cond: (id = hgg.groupid)
                             Filter: (groupid = ANY ('{11,15}'::bigint[]))
                             Rows Removed by Filter: 1
 Planning time: 0.545 ms
 Execution time: 35.113 ms
(25 rows)

----- groupid=16 has some READ host access:

zabbix=> explain analyze
SELECT   e.* FROM events e WHERE EXISTS (SELECT NULL FROM functions f,items i,hosts_groups hgg JOIN rights r ON r.id=hgg.groupid AND r.groupid IN ('11','16') WHERE e.objectid=f.triggerid AND f.itemid=i.itemid AND i.hostid=hgg.hostid GROUP BY f.triggerid HAVING MIN(r.permission)>0 AND MAX(r.permission)>='2') AND e.object='0' AND e.source='0' ORDER BY e.clock LIMIT 1 OFFSET 0;
                                                                              QUERY PLAN
-----------------------------------------------------------------------------------------------------------------------------------------------------------------------
 Limit  (cost=0.28..18.24 rows=1 width=40) (actual time=0.061..0.061 rows=1 loops=1)
   ->  Index Scan using events_2 on events e  (cost=0.28..32748.20 rows=1824 width=40) (actual time=0.061..0.061 rows=1 loops=1)
         Index Cond: ((source = 0) AND (object = 0))
         Filter: (SubPlan 1)
         Rows Removed by Filter: 6
         SubPlan 1
           ->  GroupAggregate  (cost=0.83..8.93 rows=1 width=12) (actual time=0.006..0.006 rows=0 loops=7)
                 Group Key: f.triggerid
                 Filter: ((min(r.permission) > 0) AND (max(r.permission) >= 2))
                 ->  Nested Loop  (cost=0.83..8.91 rows=1 width=12) (actual time=0.004..0.005 rows=0 loops=7)
                       ->  Nested Loop  (cost=0.70..8.72 rows=1 width=16) (actual time=0.004..0.004 rows=0 loops=7)
                             ->  Nested Loop  (cost=0.56..8.57 rows=1 width=16) (actual time=0.003..0.003 rows=0 loops=7)
                                   ->  Index Scan using functions_1 on functions f  (cost=0.28..4.28 rows=1 width=16) (actual time=0.001..0.001 rows=0 loops=7)
                                         Index Cond: (e.objectid = triggerid)
                                   ->  Index Scan using items_pkey on items i  (cost=0.28..4.29 rows=1 width=16) (actual time=0.004..0.004 rows=1 loops=1)
                                         Index Cond: (itemid = f.itemid)
                             ->  Index Only Scan using hosts_groups_1 on hosts_groups hgg  (cost=0.14..0.15 rows=1 width=16) (actual time=0.003..0.003 rows=1 loops=1)
                                   Index Cond: (hostid = i.hostid)
                                   Heap Fetches: 0
                       ->  Index Scan using rights_2 on rights r  (cost=0.13..0.19 rows=1 width=12) (actual time=0.003..0.004 rows=1 loops=1)
                             Index Cond: (id = hgg.groupid)
                             Filter: (groupid = ANY ('{11,16}'::bigint[]))
 Planning time: 0.559 ms
 Execution time: 0.115 ms
(24 rows)

zabbix=> select count(*) from events e where e.object='0' AND e.source='0';
 count
-------
  4286
(1 row)