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, 40451, 49588, 2320, 2319, 
    35256, 47632, 45283, 46822, 6659, 50182, 
    48823, 46585, 15457, 40927, 49012, 
    47903, 43817, 1894, 49873, 6358, 6357, 
    41341, 35279, 47597, 1767, 18608, 1057, 
    5790, 17265, 41340
  ) 
  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 (1896,50216,40451,49588,2320,2319,35256,47632,45283,46822,6659,50182,48823,46585,15457,40927,49012,47903,43817,1894,49873,6358,6357,41341,35279,47597,1767,18608,1057,5790,17265,41340) and cscart_product_descriptions.lang_code = 'vi'"
        }
      }
    ]
  }
}