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 (
    2912, 1043, 3006, 4299, 6649, 5730, 6044, 
    5734, 43670, 4648, 31863, 20588, 5958, 
    5723, 5998, 733, 3437, 2497, 5154, 1639, 
    4045, 5416, 5418, 5476, 34554, 3196, 
    3223, 4074, 4650, 1056, 36492, 3712
  ) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.02018

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 (2912,1043,3006,4299,6649,5730,6044,5734,43670,4648,31863,20588,5958,5723,5998,733,3437,2497,5154,1639,4045,5416,5418,5476,34554,3196,3223,4074,4650,1056,36492,3712) and cscart_product_descriptions.lang_code = 'en'"
        }
      }
    ]
  }
}