[Minor] Use '--' instead of 'UN' for unknown values

diff --git a/src/plugins/lua/clickhouse.lua b/src/plugins/lua/clickhouse.lua
index 08fb25c8c393ac43e00e915a66d44185c30797b9..bd164ab65ec8c4300210d2d199d5ce4eafcb7bf9 100644 (file)
--- a/src/plugins/lua/clickhouse.lua
+++ b/src/plugins/lua/clickhouse.lua
@@ -573,7 +573,7 @@ local function clickhouse_collect(task)
 
   -- ASN information
   if settings['asn_table'] then
-    local asn, country, ipnet = 'UN', 'UN', 'UN'
+    local asn, country, ipnet = '--', '--', '--'
     local pool = task:get_mempool()
     ret = pool:get_variable("asn")
     if ret then