SELECT 
  q_discussion.object_id AS product_id, 
  AVG(
    q_discussion_rating.rating_value
  ) AS average_rating, 
  q_discussion.type AS discussion_type, 
  q_discussion.thread_id AS discussion_thread_id 
FROM 
  q_discussion 
  LEFT JOIN q_discussion_posts ON q_discussion_posts.thread_id = q_discussion.thread_id 
  AND q_discussion_posts.status = "A" 
  LEFT JOIN q_discussion_rating ON q_discussion.thread_id = q_discussion_rating.thread_id 
  AND q_discussion_rating.post_id = q_discussion_posts.post_id 
  AND q_discussion_rating.rating_value != 0 
WHERE 
  q_discussion.object_id IN (
    47678, 
    47679, 
    47680, 
    47681, 
    47682, 
    47683, 
    47684, 
    47685, 
    47686, 
    47688, 
    47690, 
    47691, 
    47692, 
    47693, 
    47694, 
    47695, 
    47696, 
    47697, 
    47698, 
    47699, 
    47700, 
    47701, 
    47702, 
    47703, 
    47705, 
    47706, 
    47707, 
    47708, 
    47709, 
    47710, 
    47711, 
    47712, 
    47714, 
    47719, 
    47720, 
    47721, 
    47722, 
    47725, 
    47730, 
    47731, 
    47732, 
    47733, 
    47734, 
    47735, 
    47736, 
    47737, 
    47738, 
    47739, 
    47740, 
    47741, 
    47742, 
    47743, 
    47744, 
    47745, 
    47746, 
    47747, 
    47748, 
    47749, 
    47750, 
    47751, 
    47752, 
    47753, 
    47754, 
    47755, 
    47756, 
    47757, 
    47758, 
    47760, 
    47761, 
    47762, 
    47763, 
    47764, 
    47765, 
    47766, 
    47767, 
    47768, 
    47769, 
    47770, 
    47771, 
    47772, 
    47773, 
    47774, 
    45784, 
    45785, 
    45786, 
    45787, 
    45788, 
    45789, 
    45790, 
    45791, 
    45792, 
    45793, 
    45794, 
    45795, 
    45796, 
    45797, 
    45798, 
    45799, 
    45800, 
    45801, 
    45802, 
    45803, 
    45804, 
    45805, 
    45806, 
    45807, 
    45808, 
    45809, 
    45810, 
    45811, 
    45812, 
    45813, 
    45814, 
    45815, 
    45816, 
    45817, 
    45818, 
    45819, 
    45820, 
    45821, 
    45822, 
    45823, 
    45824, 
    45825, 
    45826, 
    45827, 
    45828, 
    45829
  ) 
  AND q_discussion.object_type = "P" 
GROUP BY 
  q_discussion.object_id

Query time 0.00089

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "921.61"
    },
    "grouping_operation": {
      "using_filesort": false,
      "nested_loop": [
        {
          "table": {
            "table_name": "q_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": 128,
            "rows_produced_per_join": 128,
            "filtered": "100.00",
            "index_condition": "((`portal`.`q_discussion`.`object_id` in (47678,47679,47680,47681,47682,47683,47684,47685,47686,47688,47690,47691,47692,47693,47694,47695,47696,47697,47698,47699,47700,47701,47702,47703,47705,47706,47707,47708,47709,47710,47711,47712,47714,47719,47720,47721,47722,47725,47730,47731,47732,47733,47734,47735,47736,47737,47738,47739,47740,47741,47742,47743,47744,47745,47746,47747,47748,47749,47750,47751,47752,47753,47754,47755,47756,47757,47758,47760,47761,47762,47763,47764,47765,47766,47767,47768,47769,47770,47771,47772,47773,47774,45784,45785,45786,45787,45788,45789,45790,45791,45792,45793,45794,45795,45796,45797,45798,45799,45800,45801,45802,45803,45804,45805,45806,45807,45808,45809,45810,45811,45812,45813,45814,45815,45816,45817,45818,45819,45820,45821,45822,45823,45824,45825,45826,45827,45828,45829)) and (`portal`.`q_discussion`.`object_type` = 'P'))",
            "cost_info": {
              "read_cost": "281.61",
              "eval_cost": "25.60",
              "prefix_cost": "307.21",
              "data_read_per_join": "2K"
            },
            "used_columns": [
              "thread_id",
              "object_id",
              "object_type",
              "type"
            ]
          }
        },
        {
          "table": {
            "table_name": "q_discussion_posts",
            "access_type": "ref",
            "possible_keys": [
              "thread_id",
              "thread_id_2"
            ],
            "key": "thread_id",
            "used_key_parts": [
              "thread_id"
            ],
            "key_length": "3",
            "ref": [
              "portal.q_discussion.thread_id"
            ],
            "rows_examined_per_scan": 2,
            "rows_produced_per_join": 256,
            "filtered": "100.00",
            "cost_info": {
              "read_cost": "256.00",
              "eval_cost": "51.20",
              "prefix_cost": "614.41",
              "data_read_per_join": "112K"
            },
            "used_columns": [
              "post_id",
              "thread_id",
              "status"
            ],
            "attached_condition": "<if>(is_not_null_compl(q_discussion_posts), (`portal`.`q_discussion_posts`.`status` = 'A'), true)"
          }
        },
        {
          "table": {
            "table_name": "q_discussion_rating",
            "access_type": "eq_ref",
            "possible_keys": [
              "PRIMARY",
              "thread_id"
            ],
            "key": "PRIMARY",
            "used_key_parts": [
              "post_id"
            ],
            "key_length": "3",
            "ref": [
              "portal.q_discussion_posts.post_id"
            ],
            "rows_examined_per_scan": 1,
            "rows_produced_per_join": 256,
            "filtered": "100.00",
            "cost_info": {
              "read_cost": "256.00",
              "eval_cost": "51.20",
              "prefix_cost": "921.61",
              "data_read_per_join": "4K"
            },
            "used_columns": [
              "rating_value",
              "post_id",
              "thread_id"
            ],
            "attached_condition": "<if>(is_not_null_compl(q_discussion_rating), ((`portal`.`q_discussion_rating`.`thread_id` = `portal`.`q_discussion`.`thread_id`) and (`portal`.`q_discussion_rating`.`rating_value` <> 0)), true)"
          }
        }
      ]
    }
  }
}