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 (
    1881, 4239, 4241, 1884, 47190, 45028, 
    47191, 47192, 45027, 43854, 43855, 
    47189, 47188, 45026, 50303, 50299, 
    50289, 50285, 50286, 50292, 50288, 
    50284, 50302, 50301, 50291, 50295
  ) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.00661

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": 26,
          "filtered": 100,
          "index_condition": "cscart_product_descriptions.product_id in (1881,4239,4241,1884,47190,45028,47191,47192,45027,43854,43855,47189,47188,45026,50303,50299,50289,50285,50286,50292,50288,50284,50302,50301,50291,50295) and cscart_product_descriptions.lang_code = 'en'"
        }
      }
    ]
  }
}