SELECT 
  cscart_product_descriptions.product_id, 
  cscart_product_descriptions.short_description, 
  IF(
    cscart_product_descriptions.short_description = '' 
    OR cscart_product_descriptions.short_description IS NULL, 
    cscart_product_descriptions.full_description, 
    ''
  ) AS full_description 
FROM 
  cscart_product_descriptions 
WHERE 
  cscart_product_descriptions.product_id IN (
    5578, 5472, 5457, 5588, 5462, 5579, 5590, 
    5478, 5580, 31887, 31891, 5960, 5957, 
    5961, 31894, 16802, 35733, 5448, 31893, 
    4363, 5956, 31895, 4361, 5451, 5479, 
    4366, 4360, 5591, 5485, 5587, 31889, 
    5963
  ) 
  AND cscart_product_descriptions.lang_code = 'vi'

Query time 0.00281

JSON explain

{
  "query_block": {
    "select_id": 1,
    "nested_loop": [
      {
        "table": {
          "table_name": "cscart_product_descriptions",
          "access_type": "range",
          "possible_keys": ["PRIMARY", "product_id"],
          "key": "PRIMARY",
          "key_length": "11",
          "used_key_parts": ["product_id", "lang_code"],
          "rows": 32,
          "filtered": 100,
          "index_condition": "cscart_product_descriptions.product_id in (5578,5472,5457,5588,5462,5579,5590,5478,5580,31887,31891,5960,5957,5961,31894,16802,35733,5448,31893,4363,5956,31895,4361,5451,5479,4366,4360,5591,5485,5587,31889,5963) and cscart_product_descriptions.lang_code = 'vi'"
        }
      }
    ]
  }
}