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 (
    48685, 43657, 47856, 47617, 48866, 47393, 
    47860, 48735, 47179, 48323, 48687, 
    48948, 49320, 44570, 48528, 47857, 
    47863, 47390, 48529, 48686, 48691, 
    40531, 49183, 48689, 15019, 49583, 
    47618, 49221, 49149, 48669, 48324, 
    48690
  ) 
  AND cscart_product_descriptions.lang_code = 'vi'

Query time 0.00804

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 (48685,43657,47856,47617,48866,47393,47860,48735,47179,48323,48687,48948,49320,44570,48528,47857,47863,47390,48529,48686,48691,40531,49183,48689,15019,49583,47618,49221,49149,48669,48324,48690) and cscart_product_descriptions.lang_code = 'vi'"
        }
      }
    ]
  }
}