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 (
    926, 1266, 26856, 26851, 41418, 37302, 
    32360, 37284, 41368, 1542, 3464, 4865, 
    6103, 26857, 41387, 41423, 5635, 31645, 
    41367, 2259, 37942, 2449, 31904, 31618, 
    41134, 6102, 4793, 41102, 36494, 41428, 
    37289, 2248
  ) 
  AND cscart_product_descriptions.lang_code = 'vi'

Query time 0.01197

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 (926,1266,26856,26851,41418,37302,32360,37284,41368,1542,3464,4865,6103,26857,41387,41423,5635,31645,41367,2259,37942,2449,31904,31618,41134,6102,4793,41102,36494,41428,37289,2248) and cscart_product_descriptions.lang_code = 'vi'"
        }
      }
    ]
  }
}