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 (
    83015, 83546, 83547, 90847, 90848, 90926, 
    90927, 90743, 90744, 90746, 90747, 
    90749, 90750, 90752, 90753, 84319, 
    84320, 85275, 89759, 90742, 91149, 
    91150, 86480, 86756, 82799, 82800, 
    82872, 82873, 82945, 82946
  ) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.00078

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "13.52"
    },
    "table": {
      "table_name": "cscart_product_descriptions",
      "access_type": "range",
      "possible_keys": [
        "PRIMARY",
        "product_id"
      ],
      "key": "PRIMARY",
      "used_key_parts": [
        "product_id",
        "lang_code"
      ],
      "key_length": "9",
      "rows_examined_per_scan": 30,
      "rows_produced_per_join": 30,
      "filtered": "100.00",
      "cost_info": {
        "read_cost": "10.52",
        "eval_cost": "3.00",
        "prefix_cost": "13.52",
        "data_read_per_join": "114K"
      },
      "used_columns": [
        "product_id",
        "lang_code",
        "short_description",
        "full_description"
      ],
      "attached_condition": "((`nuie_scalesta_net`.`cscart_product_descriptions`.`product_id` in (83015,83546,83547,90847,90848,90926,90927,90743,90744,90746,90747,90749,90750,90752,90753,84319,84320,85275,89759,90742,91149,91150,86480,86756,82799,82800,82872,82873,82945,82946)) and (`nuie_scalesta_net`.`cscart_product_descriptions`.`lang_code` = 'en'))"
    }
  }
}