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 (
    100769, 100770, 100771, 100772, 100773, 
    100774, 100775, 100776, 100777, 100778, 
    100779, 100780, 100781, 100782, 100783, 
    100784, 100785, 100786, 100787, 100788, 
    100841, 100842, 100843, 100844, 100845, 
    100846, 100847, 100848, 100853, 100854, 
    100855, 100856, 100863, 100864, 100865, 
    100866, 100871, 100872, 100873, 100874, 
    100875, 100876, 101054, 101656, 101657, 
    101658, 101659
  ) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.00096

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "21.17"
    },
    "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": 47,
      "rows_produced_per_join": 47,
      "filtered": "100.00",
      "cost_info": {
        "read_cost": "16.48",
        "eval_cost": "4.70",
        "prefix_cost": "21.18",
        "data_read_per_join": "179K"
      },
      "used_columns": [
        "product_id",
        "lang_code",
        "short_description",
        "full_description"
      ],
      "attached_condition": "((`nuie_scalesta_net`.`cscart_product_descriptions`.`product_id` in (100769,100770,100771,100772,100773,100774,100775,100776,100777,100778,100779,100780,100781,100782,100783,100784,100785,100786,100787,100788,100841,100842,100843,100844,100845,100846,100847,100848,100853,100854,100855,100856,100863,100864,100865,100866,100871,100872,100873,100874,100875,100876,101054,101656,101657,101658,101659)) and (`nuie_scalesta_net`.`cscart_product_descriptions`.`lang_code` = 'en'))"
    }
  }
}