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 (
    20838, 41136, 41146, 2623, 37897, 37890, 
    41126, 41107, 41129, 41425, 36522, 
    44552, 47432, 36520, 37891, 37883, 
    27368, 37884, 41132, 41118, 41120, 
    37893, 41109, 47433, 47415, 47430
  ) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.01019

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": 26,
          "filtered": 100,
          "index_condition": "cscart_product_descriptions.product_id in (20838,41136,41146,2623,37897,37890,41126,41107,41129,41425,36522,44552,47432,36520,37891,37883,27368,37884,41132,41118,41120,37893,41109,47433,47415,47430) and cscart_product_descriptions.lang_code = 'en'"
        }
      }
    ]
  }
}