SELECT 
  p.product_id, 
  ifnull(
    count(dp.post_id), 
    0
  ) as discussion_amount_posts 
FROM 
  q_discussion 
  INNER JOIN q_products as p ON (
    q_discussion.object_id = p.product_id
  ) 
  INNER JOIN q_discussion_posts as dp ON (
    q_discussion.thread_id = dp.thread_id 
    AND q_discussion.object_type = 'P'
  ) 
WHERE 
  dp.status = 'A' 
  and p.product_id in (
    10309, 
    10310, 
    10311, 
    10312, 
    10313, 
    10314, 
    10315, 
    10316, 
    10317, 
    10318, 
    10319, 
    10322, 
    10324, 
    10325, 
    10326, 
    1471, 
    1472, 
    1473, 
    1474, 
    1475, 
    1476, 
    1477, 
    1478, 
    1479, 
    1480, 
    1481, 
    1482, 
    1483, 
    1484, 
    1485, 
    1486, 
    1487, 
    1488, 
    1489, 
    1490, 
    1491, 
    1492, 
    1493, 
    1494, 
    1495, 
    1496, 
    1497, 
    1498, 
    1499, 
    1500, 
    1502, 
    1503, 
    1504, 
    1505, 
    1506, 
    1507, 
    1508, 
    1509, 
    1510, 
    1511, 
    1512, 
    1513, 
    1514, 
    1515, 
    1516, 
    1517, 
    1518, 
    1521, 
    1522, 
    1523, 
    1528, 
    1529, 
    1530, 
    1531, 
    1532, 
    1533, 
    1534, 
    1535, 
    1536, 
    1537, 
    1538, 
    1539, 
    1540, 
    1541, 
    1542, 
    1543, 
    1544, 
    1545, 
    1546, 
    1547, 
    1548, 
    1549, 
    1550, 
    1551, 
    1552, 
    1553, 
    1554, 
    1555, 
    1556, 
    1557, 
    1558, 
    1559, 
    1560, 
    1561, 
    1562, 
    1563, 
    1564, 
    1565, 
    1566, 
    1567, 
    1568, 
    1569, 
    1570, 
    1571, 
    1572, 
    1573, 
    1574, 
    1577, 
    1578, 
    1579, 
    1580, 
    1581, 
    1582, 
    1583, 
    1584, 
    1585, 
    1586, 
    1587, 
    1588, 
    1589, 
    1590, 
    1591, 
    1592
  ) 
GROUP BY 
  p.product_id

Query time 0.00093

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "21.61"
    },
    "grouping_operation": {
      "using_temporary_table": true,
      "using_filesort": true,
      "cost_info": {
        "sort_cost": "0.29"
      },
      "nested_loop": [
        {
          "table": {
            "table_name": "dp",
            "access_type": "ALL",
            "possible_keys": [
              "thread_id",
              "thread_id_2"
            ],
            "rows_examined_per_scan": 57,
            "rows_produced_per_join": 5,
            "filtered": "10.00",
            "cost_info": {
              "read_cost": "13.01",
              "eval_cost": "1.14",
              "prefix_cost": "14.15",
              "data_read_per_join": "2K"
            },
            "used_columns": [
              "post_id",
              "thread_id",
              "status"
            ],
            "attached_condition": "(`portal`.`dp`.`status` = 'A')"
          }
        },
        {
          "table": {
            "table_name": "q_discussion",
            "access_type": "eq_ref",
            "possible_keys": [
              "PRIMARY",
              "object_id"
            ],
            "key": "PRIMARY",
            "used_key_parts": [
              "thread_id"
            ],
            "key_length": "3",
            "ref": [
              "portal.dp.thread_id"
            ],
            "rows_examined_per_scan": 1,
            "rows_produced_per_join": 0,
            "filtered": "5.00",
            "cost_info": {
              "read_cost": "5.70",
              "eval_cost": "0.06",
              "prefix_cost": "20.99",
              "data_read_per_join": "4"
            },
            "used_columns": [
              "thread_id",
              "object_id",
              "object_type"
            ],
            "attached_condition": "((`portal`.`q_discussion`.`object_id` in (10309,10310,10311,10312,10313,10314,10315,10316,10317,10318,10319,10322,10324,10325,10326,1471,1472,1473,1474,1475,1476,1477,1478,1479,1480,1481,1482,1483,1484,1485,1486,1487,1488,1489,1490,1491,1492,1493,1494,1495,1496,1497,1498,1499,1500,1502,1503,1504,1505,1506,1507,1508,1509,1510,1511,1512,1513,1514,1515,1516,1517,1518,1521,1522,1523,1528,1529,1530,1531,1532,1533,1534,1535,1536,1537,1538,1539,1540,1541,1542,1543,1544,1545,1546,1547,1548,1549,1550,1551,1552,1553,1554,1555,1556,1557,1558,1559,1560,1561,1562,1563,1564,1565,1566,1567,1568,1569,1570,1571,1572,1573,1574,1577,1578,1579,1580,1581,1582,1583,1584,1585,1586,1587,1588,1589,1590,1591,1592)) and (`portal`.`q_discussion`.`object_type` = 'P'))"
          }
        },
        {
          "table": {
            "table_name": "p",
            "access_type": "eq_ref",
            "possible_keys": [
              "PRIMARY"
            ],
            "key": "PRIMARY",
            "used_key_parts": [
              "product_id"
            ],
            "key_length": "3",
            "ref": [
              "portal.q_discussion.object_id"
            ],
            "rows_examined_per_scan": 1,
            "rows_produced_per_join": 0,
            "filtered": "100.00",
            "using_index": true,
            "cost_info": {
              "read_cost": "0.29",
              "eval_cost": "0.06",
              "prefix_cost": "21.33",
              "data_read_per_join": "1K"
            },
            "used_columns": [
              "product_id"
            ]
          }
        }
      ]
    }
  }
}