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 (
    93363, 93364, 93365, 93366, 93367, 93368, 
    93369, 93370, 93371, 93372, 93373, 
    93374, 93375, 93376, 93377, 93378, 
    93379, 93380, 93381, 93382, 93383, 
    93384, 93385, 93386, 93387, 93388, 
    93389, 93390, 93391, 93392, 93393, 
    93394, 93395, 93396, 93397, 93398, 
    93399, 93400, 93407, 93408, 93409, 
    93410, 93411, 93412, 93413, 93414, 
    93415, 93416, 93417, 93418, 93419, 
    93420, 93421, 93422, 93423, 93424, 
    93425, 93426, 93427, 93428, 93429, 
    93430, 93431, 93432, 93433, 93434, 
    93435, 93436, 93437, 93438, 93439, 
    93440, 93441, 93442, 93443, 93444, 
    93445, 93446, 93447, 93448, 93449, 
    93450, 93451, 93452, 93453, 93454, 
    93455, 93456, 93457, 93458, 93459, 
    93460, 93461, 93462, 93463, 93464
  ) 
  AND cscart_discussion.object_type = "P" 
GROUP BY 
  cscart_discussion.object_id

Query time 0.00135

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 (93363,93364,93365,93366,93367,93368,93369,93370,93371,93372,93373,93374,93375,93376,93377,93378,93379,93380,93381,93382,93383,93384,93385,93386,93387,93388,93389,93390,93391,93392,93393,93394,93395,93396,93397,93398,93399,93400,93407,93408,93409,93410,93411,93412,93413,93414,93415,93416,93417,93418,93419,93420,93421,93422,93423,93424,93425,93426,93427,93428,93429,93430,93431,93432,93433,93434,93435,93436,93437,93438,93439,93440,93441,93442,93443,93444,93445,93446,93447,93448,93449,93450,93451,93452,93453,93454,93455,93456,93457,93458,93459,93460,93461,93462,93463,93464)) 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)"
          }
        }
      ]
    }
  }
}