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 (
    118, 1982, 44423, 5992, 41279, 23044, 
    44858, 5994, 31640, 44422, 2278, 6059, 
    48769, 6060, 18201, 6099, 1897, 401, 
    6058, 6061, 6063, 5890, 6062, 6057, 
    4280, 31642, 5894, 6056, 2591, 31641, 
    400, 25733
  ) 
  AND cscart_product_descriptions.lang_code = 'vi'

Query time 0.00733

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 (118,1982,44423,5992,41279,23044,44858,5994,31640,44422,2278,6059,48769,6060,18201,6099,1897,401,6058,6061,6063,5890,6062,6057,4280,31642,5894,6056,2591,31641,400,25733) and cscart_product_descriptions.lang_code = 'vi'"
        }
      }
    ]
  }
}