[Cartoweb-users] Undefined index error on FID field

[Giorgio Plazzotta]

I don't know why when I try to use the identify tool on a layer I get the
error
Class : SoapFaultWrapper
Message : Error [8, Undefined index:  FID,
C:\wamp\www\cartoweb3\coreplugins\query\server\ServerQuery.php, 147

even if of course the FID field  (internal index field) is indexed.
If i create another field and use it as index in the metadata mapfile I
don't get this error, but why? what's wrong?
in the metadata section i inserted something like this

    METADATA
      "id_attribute_string" "FID|integer"
      "query_returned_attributes" "CANTIERE"
    END

i also used the
      "exported_values" "recenter_name_string,id_attribute_string"
      "recenter_name_string" "CANTIERE"

But no success
thanx
Giorgio