LunaQL docs are incomplete.
Reference
actions
delete

delete

The delete action is used to delete documents:

users.lunaql
query({
    from({
        users(_id: 336898764327514112) {
            delete!;
        };
    });
});

This will delete a user document with the _id of "336898764327514112".

You can also define a condition:

users.lunaql
query({
	from({
		users: {
			where(["last_activity_at", "<", 2020]);
 
			delete!;
		};
	});
});

This will delete all users who have not logged in since 2019.

You can also use the softDelete action to soft delete document:

users.lunaql
query({
	from({
		users: {
			where(["last_activity_at", "<", 2020]);
 
			softDelete!;
		};
	});
});