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 (
    1896, 50216, 35256, 47632, 48823, 46585, 
    47903, 1894, 49873, 6358, 6357, 47597, 
    18608, 1057, 17265, 27359, 17259, 48980, 
    31729, 1538, 15322, 40381, 48557, 119, 
    35167, 36272, 1585, 47824, 35166, 35169, 
    1535, 47600
  ) 
  AND cscart_product_descriptions.lang_code = 'vi'

Query time 0.00703

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 (1896,50216,35256,47632,48823,46585,47903,1894,49873,6358,6357,47597,18608,1057,17265,27359,17259,48980,31729,1538,15322,40381,48557,119,35167,36272,1585,47824,35166,35169,1535,47600) and cscart_product_descriptions.lang_code = 'vi'"
        }
      }
    ]
  }
}