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 (
    9882, 8288, 8733, 8362, 8305, 8299, 9877, 
    9820, 9482, 10423, 9819, 9483
  ) 
  AND cscart_discussion.object_type = "P" 
  AND cscart_discussion.company_id = 3 
GROUP BY 
  cscart_discussion.object_id

Query time 0.00046

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
8288 B 1902
8299 B 1912
8305 B 1918
8362 B 1931
8733 B 1927
9482 B 2081
9483 B 2084
9819 B 4142
9820 B 4143
9877 B 4052
9882 B 4057
10423 D 6830