How to add a timestamp field with generation_time to a query rule with TUMBLINGWINDOW

[canob]

Hi everyone,
I'm trying to create a metric of number of DNS queries from each IP address, every 5 minutes, from DNS Server logs.
I'm using this query for the rule:
SELECT source_ip AS source_ip, COUNT(source_ip) AS count_source_ip FROM dns where tag = "dns_query" GROUP BY source_ip, TUMBLINGWINDOW(mi, 5);
And the output to a file is this one:

{"count_source_ip":9,"source_ip":"10.11.21.19"}
{"count_source_ip":9,"source_ip":"10.11.21.18"}
{"count_source_ip":9,"source_ip":"10.11.2.40"}

What I want is that the output to the file (or other sink output) has the timestamp of the generated metric event, like this:

{"timestamp": "2023-10-24 15:15:00.108","count_source_ip":9,"source_ip":"10.11.21.19"}
{"timestamp": "2023-10-24 15:15:00.108","count_source_ip":9,"source_ip":"10.11.21.18"}
{"timestamp": "2023-10-24 15:15:00.107","count_source_ip":9,"source_ip":"10.11.2.40"}

Is ok even if the timestamp is in other format (for example epoch), but I need it as part of the event, as a field.
Is that possible?
I don't know how to do it, because obviously the base events have a timestamp field, but I cannot aggregate and group over that field.
Thanks in advance for your help.

[ngjaying]

Use window_start() or window_end(). Please check https://ekuiper.org/docs/en/latest/sqls/functions/other_functions.html#window-start

[canob]

Thanks @ngjaying !