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 (
    36, 1046, 3332, 40, 1206, 1734, 5800, 
    5799, 7190, 7189, 5032, 5033, 6645, 
    6644, 4352, 5391, 5392, 6767, 6766, 
    4799, 4723, 4724, 7774, 7757, 3356, 
    5271, 5270, 5269, 5268, 4130, 4129, 
    4128, 4126, 4123, 4125, 4213, 4127, 
    4131, 4124, 1413, 1412, 1411, 1908, 
    1909, 4955, 4954, 4957, 4958, 7676, 
    7683, 7298, 7297, 5968, 2639, 5113, 
    7295, 7772, 7771, 7294, 7296, 2640, 
    7768, 7759, 7867, 7758, 7868, 2641, 
    7317, 7320, 7321, 2642, 5112, 3141, 
    7318, 3142, 2643, 3143, 7760, 7761, 
    7762, 3144, 5414, 5411, 5413, 5412, 
    5415, 4321, 4320, 4323, 4322, 4324, 
    4325, 4337, 4338, 4340, 4339
  ) 
  AND cscart_discussion.object_type = "P" 
  AND cscart_discussion.company_id = 1 
GROUP BY 
  cscart_discussion.object_id

Query time 0.00157

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "134.41"
    },
    "grouping_operation": {
      "using_filesort": false,
      "nested_loop": [
        {
          "table": {
            "table_name": "cscart_discussion",
            "access_type": "range",
            "possible_keys": [
              "object_id",
              "company_id"
            ],
            "key": "object_id",
            "used_key_parts": [
              "object_id",
              "object_type",
              "company_id"
            ],
            "key_length": "10",
            "rows_examined_per_scan": 96,
            "rows_produced_per_join": 96,
            "filtered": "100.00",
            "index_condition": "((`dbggbern`.`cscart_discussion`.`company_id` = 1) and (`dbggbern`.`cscart_discussion`.`object_id` in (36,1046,3332,40,1206,1734,5800,5799,7190,7189,5032,5033,6645,6644,4352,5391,5392,6767,6766,4799,4723,4724,7774,7757,3356,5271,5270,5269,5268,4130,4129,4128,4126,4123,4125,4213,4127,4131,4124,1413,1412,1411,1908,1909,4955,4954,4957,4958,7676,7683,7298,7297,5968,2639,5113,7295,7772,7771,7294,7296,2640,7768,7759,7867,7758,7868,2641,7317,7320,7321,2642,5112,3141,7318,3142,2643,3143,7760,7761,7762,3144,5414,5411,5413,5412,5415,4321,4320,4323,4322,4324,4325,4337,4338,4340,4339)) and (`dbggbern`.`cscart_discussion`.`object_type` = 'P'))",
            "cost_info": {
              "read_cost": "57.61",
              "eval_cost": "9.60",
              "prefix_cost": "67.21",
              "data_read_per_join": "2K"
            },
            "used_columns": [
              "thread_id",
              "object_id",
              "object_type",
              "type",
              "company_id"
            ]
          }
        },
        {
          "table": {
            "table_name": "cscart_discussion_posts",
            "access_type": "ref",
            "possible_keys": [
              "thread_id",
              "thread_id_2"
            ],
            "key": "thread_id",
            "used_key_parts": [
              "thread_id"
            ],
            "key_length": "3",
            "ref": [
              "dbggbern.cscart_discussion.thread_id"
            ],
            "rows_examined_per_scan": 1,
            "rows_produced_per_join": 96,
            "filtered": "100.00",
            "cost_info": {
              "read_cost": "24.00",
              "eval_cost": "9.60",
              "prefix_cost": "100.81",
              "data_read_per_join": "42K"
            },
            "used_columns": [
              "post_id",
              "thread_id",
              "status"
            ],
            "attached_condition": "<if>(is_not_null_compl(cscart_discussion_posts), (`dbggbern`.`cscart_discussion_posts`.`status` = 'A'), true)"
          }
        },
        {
          "table": {
            "table_name": "cscart_discussion_rating",
            "access_type": "eq_ref",
            "possible_keys": [
              "PRIMARY",
              "thread_id"
            ],
            "key": "PRIMARY",
            "used_key_parts": [
              "post_id"
            ],
            "key_length": "3",
            "ref": [
              "dbggbern.cscart_discussion_posts.post_id"
            ],
            "rows_examined_per_scan": 1,
            "rows_produced_per_join": 96,
            "filtered": "100.00",
            "cost_info": {
              "read_cost": "24.00",
              "eval_cost": "9.60",
              "prefix_cost": "134.41",
              "data_read_per_join": "1K"
            },
            "used_columns": [
              "rating_value",
              "post_id",
              "thread_id"
            ],
            "attached_condition": "<if>(is_not_null_compl(cscart_discussion_rating), ((`dbggbern`.`cscart_discussion_rating`.`thread_id` = `dbggbern`.`cscart_discussion`.`thread_id`) and (`dbggbern`.`cscart_discussion_rating`.`rating_value` <> 0)), true)"
          }
        }
      ]
    }
  }
}

Result

product_id average_rating discussion_type discussion_thread_id
36 D 58
40 D 62
1046 D 1184
1206 D 1361
1411 D 1626
1412 D 1627
1413 D 1628
1734 D 1990
1908 D 2187
1909 D 2188
2639 D 2778
2640 D 2779
2641 D 2780
2642 D 2781
2643 D 2782
3141 D 3332
3142 D 3333
3143 D 3334
3144 D 3335
3332 D 3544
3356 D 3569
4123 D 4406
4124 D 4407
4125 D 4408
4126 D 4409
4127 D 4410
4128 D 4411
4129 D 4412
4130 D 4413
4131 D 4414
4213 D 4501
4320 D 4613
4321 D 4614
4322 D 4615
4323 D 4616
4324 D 4617
4325 D 4618
4337 D 4630
4338 D 4631
4339 D 4632
4340 D 4633
4352 D 4645
4723 D 5047
4724 D 5048
4799 D 5133
4954 D 5303
4955 D 5304
4957 D 5306
4958 D 5307
5032 D 5384
5033 D 5385
5112 D 5487
5113 D 5488
5268 D 5654
5269 D 5655
5270 D 5656
5271 D 5657
5391 D 5787
5392 D 5788
5411 D 5810
5412 D 5811
5413 D 5812
5414 D 5813
5415 D 5814
5799 D 6221
5800 D 6222
5968 D 6427
6644 D 7147
6645 D 7148
6766 D 7290
6767 D 7291
7189 D 7740
7190 D 7741
7294 D 7850
7295 D 7851
7296 D 7852
7297 D 7853
7298 D 7854
7317 D 7873
7318 D 7874
7320 D 7876
7321 D 7877
7676 D 8248
7683 D 8255
7757 D 8331
7758 D 8332
7759 D 8333
7760 D 8334
7761 D 8335
7768 D 8346
7771 D 8336
7772 D 8337
7774 D 8339
7867 D 8435
7868 D 8436