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 (
    5833, 5835, 27363, 3885, 5836, 37305, 
    2566, 38146, 38145, 31652, 6529, 3601, 
    3617, 31651, 31786, 534, 46716, 286, 
    25180, 26846, 1041, 2567, 1835, 46749, 
    729, 227, 33697, 1532, 1838, 1056, 5730, 
    47904
  ) 
  AND cscart_product_descriptions.lang_code = 'vi'

Query time 0.00977

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 (5833,5835,27363,3885,5836,37305,2566,38146,38145,31652,6529,3601,3617,31651,31786,534,46716,286,25180,26846,1041,2567,1835,46749,729,227,33697,1532,1838,1056,5730,47904) and cscart_product_descriptions.lang_code = 'vi'"
        }
      }
    ]
  }
}