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 (
    34672, 36733, 1897, 401, 6577, 6058, 
    46181, 1412, 3585, 1121, 6061, 382, 
    2502, 2136, 2961, 6063, 2132, 5890, 
    3875, 6062, 44939, 3230, 112, 2286, 
    6057, 5567, 5141, 6052, 4280, 3880, 
    31642, 2513
  ) 
  AND cscart_product_descriptions.lang_code = 'vi'

Query time 0.01237

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 (34672,36733,1897,401,6577,6058,46181,1412,3585,1121,6061,382,2502,2136,2961,6063,2132,5890,3875,6062,44939,3230,112,2286,6057,5567,5141,6052,4280,3880,31642,2513) and cscart_product_descriptions.lang_code = 'vi'"
        }
      }
    ]
  }
}