group explain

the group explain.txt

Filesort
+- TEMPORARY
   table          temporary(nr,n,na)
   +- JOIN
      +- Distinct/Not-Exists
      |  +- Filter with WHERE
      |     +- Bookmark lookup
      |        +- Table
      |        |  table          na
      |        |  possible_keys  PRIMARY
      |        +- Index lookup
      |           key            na->PRIMARY
      |           possible_keys  PRIMARY
      |           key_len        4
      |           ref            apci.n.nid
      |           rows           2
      +- JOIN
         +- Filter with WHERE
         |  +- Bookmark lookup
         |     +- Table
         |     |  table          n
         |     |  possible_keys  PRIMARY,vid,node_status_type,node_type
         |     +- Unique index lookup
         |        key            n->vid
         |        possible_keys  PRIMARY,vid,node_status_type,node_type
         |        key_len        4
         |        ref            apci.nr.vid
         |        rows           1
         +- Filter with WHERE
            +- Index lookup
               key            nr->field_group_payee_nid
               possible_keys  PRIMARY,field_group_payee_nid
               key_len        5
               ref            const
               rows           1