SELECT 
  cscart_discussion.object_id AS product_id, 
  AVG(
    cscart_discussion_rating.rating_value
  ) AS average_rating, 
  cscart_discussion.type AS discussion_type, 
  cscart_discussion.thread_id AS discussion_thread_id 
FROM 
  cscart_discussion 
  LEFT JOIN cscart_discussion_posts ON cscart_discussion_posts.thread_id = cscart_discussion.thread_id 
  AND cscart_discussion_posts.status = "A" 
  LEFT JOIN cscart_discussion_rating ON cscart_discussion.thread_id = cscart_discussion_rating.thread_id 
  AND cscart_discussion_rating.post_id = cscart_discussion_posts.post_id 
  AND cscart_discussion_rating.rating_value != 0 
WHERE 
  cscart_discussion.object_id IN (
    10705, 10195, 10670, 9457, 8862, 11485, 
    10960, 10172, 10201, 10945, 397, 10188
  ) 
  AND cscart_discussion.object_type = "P" 
  AND cscart_discussion.company_id = 2 
GROUP BY 
  cscart_discussion.object_id

Query time 0.00063

Explain
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE cscart_discussion range object_id,company_id object_id 10 12 Using index condition
1 SIMPLE cscart_discussion_posts ref thread_id,thread_id_2 thread_id 3 mahm3t_cs443.cscart_discussion.thread_id 4 Using where
1 SIMPLE cscart_discussion_rating eq_ref PRIMARY,thread_id PRIMARY 3 mahm3t_cs443.cscart_discussion_posts.post_id 1 Using where

Result

product_id average_rating discussion_type discussion_thread_id
397 B 43
8862 B 4019
9457 B 1455
10172 5.0000 B 4664
10188 B 8508
10195 B 5448
10201 B 8507
10670 B 12077
10705 B 10253
10945 B 10865
10960 D 12178
11485 D 12114