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 (
    93877, 93878, 93879, 93880, 93881, 94034, 
    94035, 94036, 94037, 94038, 94039, 
    94040, 94041, 94042, 94043, 94044, 
    94045, 94046, 94047, 94048, 94049, 
    94050, 94051, 94052, 94053, 94054, 
    94055, 94056, 94057, 94058, 94059, 
    94060, 94061, 94062, 94063, 94161, 
    94162, 94163, 94164, 94333, 94334, 
    94335, 94336, 94337, 94338, 94339, 
    94340, 94341, 94342, 94343, 94344, 
    94345, 94346, 94347, 94348, 94349, 
    94350, 94351, 94352, 94353, 94354, 
    94355, 94356, 94357, 94358, 94359, 
    94360, 94361, 94362, 94363, 94364, 
    94365, 94366, 94435, 94442, 94443, 
    94444, 94445, 94446, 94592, 94593, 
    94594, 94650, 94662, 94766, 94767, 
    94768, 94769, 94770, 94771, 94772, 
    94773, 94774, 94775, 94776, 94777
  ) 
  AND cscart_discussion.object_type = "P" 
GROUP BY 
  cscart_discussion.object_id

Query time 0.00141

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "110.66"
    },
    "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": 96,
            "rows_produced_per_join": 96,
            "filtered": "100.00",
            "index_condition": "((`nuie_scalesta_net`.`cscart_discussion`.`object_id` in (93877,93878,93879,93880,93881,94034,94035,94036,94037,94038,94039,94040,94041,94042,94043,94044,94045,94046,94047,94048,94049,94050,94051,94052,94053,94054,94055,94056,94057,94058,94059,94060,94061,94062,94063,94161,94162,94163,94164,94333,94334,94335,94336,94337,94338,94339,94340,94341,94342,94343,94344,94345,94346,94347,94348,94349,94350,94351,94352,94353,94354,94355,94356,94357,94358,94359,94360,94361,94362,94363,94364,94365,94366,94435,94442,94443,94444,94445,94446,94592,94593,94594,94650,94662,94766,94767,94768,94769,94770,94771,94772,94773,94774,94775,94776,94777)) and (`nuie_scalesta_net`.`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"
            ]
          }
        },
        {
          "table": {
            "table_name": "cscart_discussion_posts",
            "access_type": "ref",
            "possible_keys": [
              "thread_id",
              "thread_id_2"
            ],
            "key": "thread_id_2",
            "used_key_parts": [
              "thread_id",
              "status"
            ],
            "key_length": "6",
            "ref": [
              "nuie_scalesta_net.cscart_discussion.thread_id",
              "const"
            ],
            "rows_examined_per_scan": 1,
            "rows_produced_per_join": 96,
            "filtered": "100.00",
            "using_index": true,
            "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"
            ]
          }
        },
        {
          "table": {
            "table_name": "cscart_discussion_rating",
            "access_type": "ALL",
            "possible_keys": [
              "PRIMARY",
              "thread_id"
            ],
            "rows_examined_per_scan": 1,
            "rows_produced_per_join": 96,
            "filtered": "100.00",
            "using_join_buffer": "hash join",
            "cost_info": {
              "read_cost": "0.25",
              "eval_cost": "9.60",
              "prefix_cost": "110.66",
              "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)"
          }
        }
      ]
    }
  }
}