SELECT 
  p.product_id, 
  ifnull(
    count(dp.post_id), 
    0
  ) as discussion_amount_posts 
FROM 
  cscart_discussion 
  INNER JOIN cscart_products as p ON (
    cscart_discussion.object_id = p.product_id
  ) 
  INNER JOIN cscart_discussion_posts as dp ON (
    cscart_discussion.thread_id = dp.thread_id 
    AND cscart_discussion.object_type = 'P' 
    AND cscart_discussion.company_id = 1
  ) 
WHERE 
  dp.status = 'A' 
  and p.product_id in (
    51083, 22715, 51082, 51085, 51081, 51088, 
    51087, 22713, 51086, 51089, 51090, 
    51092, 51093, 22714, 51091, 51095, 
    51096, 51097, 51098, 51100, 51099, 
    22716, 51103, 22712, 51105, 51102, 
    51101, 51205, 51204, 51203, 51202, 
    125, 51209, 51208, 51207, 51206, 124, 
    51221, 137, 51224, 51223, 51232, 12, 
    51238, 51237, 51236, 51235, 51234, 
    51233, 51246, 51245, 51244, 35, 51248, 
    51247, 51256, 51255, 51254, 33, 32, 
    51265, 51264, 51263, 51262, 51261, 
    51260, 51259, 110, 51281, 51280, 51279, 
    51278, 51282, 7, 51289, 51288, 51287, 
    51286, 51285, 51284, 51283, 8, 51294, 
    51293, 51291, 51290, 94
  ) 
GROUP BY 
  p.product_id

Query time 0.00056

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}