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 (
    93890, 93891, 93892, 93893, 94023, 94073, 
    94117, 94119, 94120, 94121, 94122, 
    94123, 94124, 94125, 94126, 94127, 
    94128, 94129, 94130, 94131, 94132, 
    94133, 94134, 94135, 94136, 94137, 
    94138, 94139, 94140, 94141, 94142, 
    94143, 94144, 94145, 94146, 94147, 
    94148, 94149, 94150, 94151, 94152, 
    94153, 94154, 94155, 94156, 94157, 
    94158, 94159, 94160, 94381, 94428, 
    94452, 94453, 94454, 94455, 94456, 
    94457, 94458, 94459, 94460, 94461, 
    94462, 94558, 94559, 94560, 94561, 
    94562, 94563, 94564, 94565, 94566, 
    94567, 94568, 94569, 94570, 94571, 
    94572, 94583, 94584, 94585, 94586, 
    94587, 94588, 94604, 94605, 94606, 
    94607, 94608, 94609, 94610, 94611, 
    94612, 94613, 94614, 94615, 94616
  ) 
  AND cscart_discussion.object_type = "P" 
GROUP BY 
  cscart_discussion.object_id

Query time 0.00058

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 (93890,93891,93892,93893,94023,94073,94117,94119,94120,94121,94122,94123,94124,94125,94126,94127,94128,94129,94130,94131,94132,94133,94134,94135,94136,94137,94138,94139,94140,94141,94142,94143,94144,94145,94146,94147,94148,94149,94150,94151,94152,94153,94154,94155,94156,94157,94158,94159,94160,94381,94428,94452,94453,94454,94455,94456,94457,94458,94459,94460,94461,94462,94558,94559,94560,94561,94562,94563,94564,94565,94566,94567,94568,94569,94570,94571,94572,94583,94584,94585,94586,94587,94588,94604,94605,94606,94607,94608,94609,94610,94611,94612,94613,94614,94615,94616)) 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",
            "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": 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), (`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": 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)"
          }
        }
      ]
    }
  }
}