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 (
    47594, 43853, 794, 5774, 804, 47607, 
    41012, 38128, 786, 41019, 47260, 44764, 
    984, 792, 47668, 44763, 6544, 47256, 
    47570, 47487, 47609, 35697, 47667, 
    35712, 35696, 47617, 47485, 35684, 
    47616, 2047, 35693, 50039
  ) 
  AND cscart_product_descriptions.lang_code = 'vi'

Query time 0.01307

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 (47594,43853,794,5774,804,47607,41012,38128,786,41019,47260,44764,984,792,47668,44763,6544,47256,47570,47487,47609,35697,47667,35712,35696,47617,47485,35684,47616,2047,35693,50039) and cscart_product_descriptions.lang_code = 'vi'"
        }
      }
    ]
  }
}