CREATE OR REPLACE FUNCTION zbx_convert_events() RETURNS SETOF events
AS
$BODY$
       DECLARE prev_triggerid bigint;
       DECLARE prev_value integer;
       r RECORD;
BEGIN

     FOR r IN
               SELECT e.eventid, e.objectid, e.value, t.type as type
                       FROM events e
                       JOIN triggers t ON t.triggerid = e.objectid
                       WHERE e.source = 0              
                               AND e.object = 0       
                               AND e.value IN (0,1)  
                                             ORDER BY e.objectid, e.clock, e.eventid
     LOOP

               IF prev_triggerid IS NULL OR prev_triggerid <> r.objectid THEN
                       prev_value := NULL;
               END IF;

               IF r.value = 0 THEN 
                       IF prev_value IS NULL OR prev_value = 1 THEN
                               UPDATE events set value_changed = 1 WHERE eventid = r.eventid;
                       END IF;
               ELSE                   
                       IF r.type = 1 OR prev_value IS NULL OR prev_value = 0 THEN
                               UPDATE events set value_changed = 1 WHERE eventid = r.eventid;
                       END IF;
               END IF;

               prev_value := r.value;
               prev_triggerid := r.objectid;

       END LOOP;

END;
$BODY$
LANGUAGE 'plpgsql' ;

CREATE OR REPLACE FUNCTION zbx_convert_events() RETURNS BOOLEAN AS $$
       DECLARE prev_triggerid bigint;
       DECLARE prev_value integer;
       r RECORD;
BEGIN

     FOR r IN
               SELECT e.eventid, e.objectid, e.value, t.type as type
                       FROM events e
                       JOIN triggers t ON t.triggerid = e.objectid
                       WHERE e.source = 0              
                               AND e.object = 0       
                               AND e.value IN (0,1)  
                                             ORDER BY e.objectid, e.clock, e.eventid
     LOOP

               IF prev_triggerid IS NULL OR prev_triggerid <> r.objectid THEN
                       prev_value := NULL;
               END IF;

               IF r.value = 0 THEN 
                       IF prev_value IS NULL OR prev_value = 1 THEN
                               UPDATE events set value_changed = 1 WHERE eventid = r.eventid;
                       END IF;
               ELSE                   
                       IF r.type = 1 OR prev_value IS NULL OR prev_value = 0 THEN
                               UPDATE events set value_changed = 1 WHERE eventid = r.eventid;
                       END IF;
               END IF;

               prev_value := r.value;
               prev_triggerid := r.objectid;

       END LOOP;

      RETURN 1;
END;
$$ LANGUAGE plpgsql;

SELECT zbx_convert_events();

DROP FUNCTION zbx_convert_events();

ERROR:  language "plpgsql" does not exist
HINT:  Use CREATE LANGUAGE to load the language into the database.
ERROR:  function zbx_convert_events() does not exist
LINE 1: SELECT zbx_convert_events();
               ^
HINT:  No function matches the given name and argument types. You might need to add explicit type casts.
ERROR:  function zbx_convert_events() does not exist