mysql> explain select item_id from items left join items_text using (item_id) where match (title, content) against ('Krish*' in boolean mode)\G
*************************** 1. row ***************************
           id: 1
  select_type: SIMPLE
        table: items
         type: ALL
possible_keys: NULL
          key: NULL
      key_len: NULL
          ref: NULL
         rows: 670670
        Extra: 
*************************** 2. row ***************************
           id: 1
  select_type: SIMPLE
        table: items_text
         type: eq_ref
possible_keys: PRIMARY
          key: PRIMARY
      key_len: 8
          ref: grazr.items.item_id
         rows: 1
        Extra: Using where
2 rows in set (0.00 sec)

mysql> explain select item_id from items left join items_text using (item_id) where match (title, content) against ('Krishna' in boolean mode)\G
*************************** 1. row ***************************
           id: 1
  select_type: SIMPLE
        table: items
         type: ALL
possible_keys: NULL
          key: NULL
      key_len: NULL
          ref: NULL
         rows: 670678
        Extra: 
*************************** 2. row ***************************
           id: 1
  select_type: SIMPLE
        table: items_text
         type: eq_ref
possible_keys: PRIMARY
          key: PRIMARY
      key_len: 8
          ref: grazr.items.item_id
         rows: 1
        Extra: Using where
2 rows in set (0.00 sec)