WSO2 SIDDHI查询类似“不存在”

Question

I have not found any way to express a query with something like "not exists".

For example, to simply test that all the devices are ok, or send an alert if one of them is missing for a given time, a query like :

from every myDeviceTable
join not exists myEvents[myEvents.DeviceID == myDeviceTable.ID]#window.time(5 sec)
select myDeviceTable.ID as deviceID, "Message...", ...
insert into myAlertTable

Some help please ?

Regards.

Answer 1

You can use the not keyword as follows: (Assuming myDeviceTable is an event table)

from myEvents[not(DeviceID == myDeviceTable.ID in myDeviceTable)] 
select DeviceID, "message..",
insert into myAlertTable;

If you want to select attributes that resides only inside the table, use another join query for that using the outputs of this query.