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 (
    3867, 23158, 5790, 33723, 3868, 3869, 
    27359, 5789, 3870, 3872, 35782, 40445, 
    40442, 22172, 47024, 1278, 3871, 41293, 
    40446, 855, 5786, 47020, 3876, 1975, 
    40443, 27353, 2873, 2854, 3713, 6369, 
    48558, 40449
  ) 
  AND cscart_product_descriptions.lang_code = 'vi'

Query time 0.02532

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 (3867,23158,5790,33723,3868,3869,27359,5789,3870,3872,35782,40445,40442,22172,47024,1278,3871,41293,40446,855,5786,47020,3876,1975,40443,27353,2873,2854,3713,6369,48558,40449) and cscart_product_descriptions.lang_code = 'vi'"
        }
      }
    ]
  }
}