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 (
    9937, 9573, 9574, 9575, 9576, 9577, 9672, 
    9578, 9638, 9643, 9671, 9581, 9582, 
    9584, 9585, 8687, 9685, 9954, 9681, 
    9682, 9955, 9683, 9686, 9956, 9758, 
    9612, 9730, 9616, 8933, 9732, 9735, 
    9587, 9589, 9599, 8936, 9565, 9600, 
    9604, 9606, 9947, 9621, 9610, 8939, 
    9611, 9664, 9665, 9748, 9564, 9750, 
    9623, 9958, 9960, 9666, 9952, 9959, 
    9949, 9753, 9944, 9754, 9562, 9756, 
    8983, 9673, 9961, 9957, 9757, 9626, 
    9627, 9629, 9630, 9632, 9633, 9635, 
    9640, 9945, 9950, 9641, 8945, 9625, 
    9645, 9647, 9677, 9648, 9953, 9650, 
    9921, 8941, 9922, 9923, 9925, 9924, 
    9745, 9651, 9652, 9746, 9654, 9926, 
    9655, 9927, 9734
  ) 
  AND cscart_discussion.object_type = "P" 
  AND cscart_discussion.company_id = 1 
GROUP BY 
  cscart_discussion.object_id

Query time 0.00111

JSON explain

{
  "query_block": {
    "select_id": 1,
    "nested_loop": [
      {
        "table": {
          "table_name": "cscart_discussion",
          "access_type": "range",
          "possible_keys": ["object_id", "idx_company_id"],
          "key": "object_id",
          "key_length": "10",
          "used_key_parts": ["object_id", "object_type", "company_id"],
          "rows": 100,
          "filtered": 100,
          "index_condition": "cscart_discussion.company_id = 1 and cscart_discussion.object_id in (9937,9573,9574,9575,9576,9577,9672,9578,9638,9643,9671,9581,9582,9584,9585,8687,9685,9954,9681,9682,9955,9683,9686,9956,9758,9612,9730,9616,8933,9732,9735,9587,9589,9599,8936,9565,9600,9604,9606,9947,9621,9610,8939,9611,9664,9665,9748,9564,9750,9623,9958,9960,9666,9952,9959,9949,9753,9944,9754,9562,9756,8983,9673,9961,9957,9757,9626,9627,9629,9630,9632,9633,9635,9640,9945,9950,9641,8945,9625,9645,9647,9677,9648,9953,9650,9921,8941,9922,9923,9925,9924,9745,9651,9652,9746,9654,9926,9655,9927,9734) and cscart_discussion.object_type = 'P'"
        }
      },
      {
        "table": {
          "table_name": "cscart_discussion_posts",
          "access_type": "ref",
          "possible_keys": ["thread_id", "thread_id_2"],
          "key": "thread_id_2",
          "key_length": "6",
          "used_key_parts": ["thread_id", "status"],
          "ref": ["lillyshop_lillyshop.cscart_discussion.thread_id", "const"],
          "rows": 2,
          "filtered": 100,
          "attached_condition": "trigcond(cscart_discussion_posts.`status` = 'A')"
        }
      },
      {
        "table": {
          "table_name": "cscart_discussion_rating",
          "access_type": "eq_ref",
          "possible_keys": ["PRIMARY", "thread_id"],
          "key": "PRIMARY",
          "key_length": "3",
          "used_key_parts": ["post_id"],
          "ref": ["lillyshop_lillyshop.cscart_discussion_posts.post_id"],
          "rows": 1,
          "filtered": 100,
          "attached_condition": "trigcond(cscart_discussion_rating.thread_id = cscart_discussion.thread_id and cscart_discussion_rating.rating_value <> 0 and trigcond(cscart_discussion_posts.post_id is not null))"
        }
      }
    ]
  }
}