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 (
    101143, 101144, 101145, 101146, 101147, 
    101148, 101149, 101150, 101151, 101152, 
    101153, 101154, 101155, 101156, 101157, 
    101158, 101159, 101160, 101161, 101162, 
    101163, 101164, 101165, 101166, 101167, 
    101168, 101169, 101170, 101171, 101172, 
    101173, 101174, 101175, 101176, 101177, 
    101178, 101179, 101180, 101181, 101182, 
    101183, 101184, 101185, 101186, 101187, 
    101188, 101189, 101190, 101191, 101192, 
    101193, 101194, 101195, 101196, 101197, 
    101198, 101199, 101200, 101201, 101202, 
    101203, 101204, 101205, 101206, 101207, 
    101208, 101209, 101210, 101211, 101212, 
    101213, 101214, 101215, 101216, 101217, 
    101218, 101219, 101220, 101221, 101222, 
    101223, 101224, 101225, 101226, 101227, 
    101228, 101229, 101230, 101231, 101232, 
    101233, 101234, 101235, 101236, 101237, 
    101238
  ) 
  AND cscart_discussion.object_type = "P" 
GROUP BY 
  cscart_discussion.object_id

Query time 0.00130

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 (101143,101144,101145,101146,101147,101148,101149,101150,101151,101152,101153,101154,101155,101156,101157,101158,101159,101160,101161,101162,101163,101164,101165,101166,101167,101168,101169,101170,101171,101172,101173,101174,101175,101176,101177,101178,101179,101180,101181,101182,101183,101184,101185,101186,101187,101188,101189,101190,101191,101192,101193,101194,101195,101196,101197,101198,101199,101200,101201,101202,101203,101204,101205,101206,101207,101208,101209,101210,101211,101212,101213,101214,101215,101216,101217,101218,101219,101220,101221,101222,101223,101224,101225,101226,101227,101228,101229,101230,101231,101232,101233,101234,101235,101236,101237,101238)) 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)"
          }
        }
      ]
    }
  }
}