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 (
    1977, 3578, 44944, 119, 3864, 43825, 
    2291, 27356, 35167, 35165, 35174, 35176, 
    35173, 35170, 35172, 35171, 5783, 31911, 
    44947, 3861, 6092, 35731, 23261, 2288, 
    40448, 40382, 118, 1982, 36272, 47656, 
    2238, 49192
  ) 
  AND cscart_product_descriptions.lang_code = 'vi'

Query time 0.00557

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 (1977,3578,44944,119,3864,43825,2291,27356,35167,35165,35174,35176,35173,35170,35172,35171,5783,31911,44947,3861,6092,35731,23261,2288,40448,40382,118,1982,36272,47656,2238,49192) and cscart_product_descriptions.lang_code = 'vi'"
        }
      }
    ]
  }
}