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 (
    92067, 92068, 92069, 92070, 92071, 92072, 
    92073, 92083, 92084, 92085, 92086, 
    92087, 92088, 92089, 84018, 84019, 
    84020, 84021, 83974, 83975, 83976, 
    83977, 92066, 92082, 90073, 89179, 
    86383, 83095, 84101, 93039, 93040, 
    93041, 93042, 93043, 93044, 93045, 
    93046, 94718, 94722, 94727, 94731, 
    94735, 94739, 94743, 94747, 97025, 
    97842, 97846, 97851, 97855, 97859, 
    97863, 97867, 97871, 97911, 97912, 
    97913, 97914, 97943, 97944, 97945, 
    97946, 97968, 98107, 98108, 98109, 
    98110, 98111, 98112, 98113, 98114, 
    98351, 98352, 98353, 98354, 98355, 
    98356, 98357, 98358, 98359, 98360, 
    98361, 98362, 98363, 98364, 98365, 
    98366, 98685, 100145, 100891
  ) 
  AND cscart_discussion.object_type = "P" 
GROUP BY 
  cscart_discussion.object_id

Query time 0.00153

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "103.76"
    },
    "grouping_operation": {
      "using_temporary_table": true,
      "using_filesort": false,
      "nested_loop": [
        {
          "table": {
            "table_name": "cscart_discussion",
            "access_type": "range",
            "possible_keys": [
              "object_id"
            ],
            "key": "object_id",
            "used_key_parts": [
              "object_id",
              "object_type"
            ],
            "key_length": "6",
            "rows_examined_per_scan": 90,
            "rows_produced_per_join": 90,
            "filtered": "100.00",
            "index_condition": "((`nuie_scalesta_net`.`cscart_discussion`.`object_id` in (92067,92068,92069,92070,92071,92072,92073,92083,92084,92085,92086,92087,92088,92089,84018,84019,84020,84021,83974,83975,83976,83977,92066,92082,90073,89179,86383,83095,84101,93039,93040,93041,93042,93043,93044,93045,93046,94718,94722,94727,94731,94735,94739,94743,94747,97025,97842,97846,97851,97855,97859,97863,97867,97871,97911,97912,97913,97914,97943,97944,97945,97946,97968,98107,98108,98109,98110,98111,98112,98113,98114,98351,98352,98353,98354,98355,98356,98357,98358,98359,98360,98361,98362,98363,98364,98365,98366,98685,100145,100891)) and (`nuie_scalesta_net`.`cscart_discussion`.`object_type` = 'P'))",
            "cost_info": {
              "read_cost": "54.01",
              "eval_cost": "9.00",
              "prefix_cost": "63.01",
              "data_read_per_join": "2K"
            },
            "used_columns": [
              "thread_id",
              "object_id",
              "object_type",
              "type"
            ]
          }
        },
        {
          "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": [
              "nuie_scalesta_net.cscart_discussion.thread_id"
            ],
            "rows_examined_per_scan": 1,
            "rows_produced_per_join": 90,
            "filtered": "100.00",
            "cost_info": {
              "read_cost": "22.50",
              "eval_cost": "9.00",
              "prefix_cost": "94.51",
              "data_read_per_join": "39K"
            },
            "used_columns": [
              "post_id",
              "thread_id",
              "status"
            ],
            "attached_condition": "<if>(is_not_null_compl(cscart_discussion_posts), (`nuie_scalesta_net`.`cscart_discussion_posts`.`status` = 'A'), true)"
          }
        },
        {
          "table": {
            "table_name": "cscart_discussion_rating",
            "access_type": "ALL",
            "possible_keys": [
              "PRIMARY",
              "thread_id"
            ],
            "rows_examined_per_scan": 1,
            "rows_produced_per_join": 90,
            "filtered": "100.00",
            "using_join_buffer": "hash join",
            "cost_info": {
              "read_cost": "0.25",
              "eval_cost": "9.00",
              "prefix_cost": "103.76",
              "data_read_per_join": "1K"
            },
            "used_columns": [
              "rating_value",
              "post_id",
              "thread_id"
            ],
            "attached_condition": "<if>(is_not_null_compl(cscart_discussion_rating), ((`nuie_scalesta_net`.`cscart_discussion_rating`.`post_id` = `nuie_scalesta_net`.`cscart_discussion_posts`.`post_id`) and (`nuie_scalesta_net`.`cscart_discussion_rating`.`thread_id` = `nuie_scalesta_net`.`cscart_discussion`.`thread_id`) and (`nuie_scalesta_net`.`cscart_discussion_rating`.`rating_value` <> 0)), true)"
          }
        }
      ]
    }
  }
}