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 (
    92557, 91938, 91937, 91939, 91940, 91941, 
    91942, 91943, 82403, 82410, 82424, 
    82362, 82360, 82404, 82342, 82367, 
    82338, 82337, 89595, 89596, 89597, 
    82336, 91936, 86810, 82375, 89590, 
    89589, 86806, 86809, 94023, 94696, 
    94697, 96295, 96298, 96708, 96718, 
    96719, 96720, 96724, 96734, 96735, 
    96738, 96743, 96758, 96759, 96764, 
    96775, 97820, 97821, 98258, 98259, 
    98260, 98261, 98262, 98263, 98264, 
    98265, 98690, 98693, 98694, 100374, 
    100375, 100380, 100381, 100382, 100383, 
    100598, 100601, 101635, 101636, 101639, 
    101640, 101644, 101645, 101646, 101647, 
    101648, 101649, 101650, 101651, 101652, 
    101653
  ) 
  AND cscart_discussion.object_type = "P" 
GROUP BY 
  cscart_discussion.object_id

Query time 0.00143

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "94.56"
    },
    "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": 82,
            "rows_produced_per_join": 82,
            "filtered": "100.00",
            "index_condition": "((`nuie_scalesta_net`.`cscart_discussion`.`object_id` in (92557,91938,91937,91939,91940,91941,91942,91943,82403,82410,82424,82362,82360,82404,82342,82367,82338,82337,89595,89596,89597,82336,91936,86810,82375,89590,89589,86806,86809,94023,94696,94697,96295,96298,96708,96718,96719,96720,96724,96734,96735,96738,96743,96758,96759,96764,96775,97820,97821,98258,98259,98260,98261,98262,98263,98264,98265,98690,98693,98694,100374,100375,100380,100381,100382,100383,100598,100601,101635,101636,101639,101640,101644,101645,101646,101647,101648,101649,101650,101651,101652,101653)) and (`nuie_scalesta_net`.`cscart_discussion`.`object_type` = 'P'))",
            "cost_info": {
              "read_cost": "49.21",
              "eval_cost": "8.20",
              "prefix_cost": "57.41",
              "data_read_per_join": "1K"
            },
            "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": 82,
            "filtered": "100.00",
            "cost_info": {
              "read_cost": "20.50",
              "eval_cost": "8.20",
              "prefix_cost": "86.11",
              "data_read_per_join": "35K"
            },
            "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": 82,
            "filtered": "100.00",
            "using_join_buffer": "hash join",
            "cost_info": {
              "read_cost": "0.25",
              "eval_cost": "8.20",
              "prefix_cost": "94.56",
              "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)"
          }
        }
      ]
    }
  }
}