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 (
    846, 845, 844, 832, 829, 828, 822, 817, 
    816, 662, 814, 806, 805, 804, 803, 802, 
    801, 800, 799, 798, 797, 796, 795, 792, 
    787, 786, 782, 819, 781, 765, 764, 763, 
    762, 760, 758, 752, 751, 750, 749, 747, 
    744, 743, 742, 741, 732, 731, 727, 725, 
    724, 723, 809, 810, 720, 718, 717, 716, 
    715, 713, 709, 708, 707, 705, 701, 697, 
    696, 695, 693, 682, 676, 673, 671, 670, 
    664, 663, 658, 657, 656, 651, 650, 647, 
    645, 644, 641, 639, 636, 624, 622, 620, 
    619, 618, 616, 615, 608, 607, 600, 597
  ) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.00237

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "67.21"
    },
    "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": 96,
      "rows_produced_per_join": 96,
      "filtered": "100.00",
      "index_condition": "((`betaatif_store`.`cscart_product_descriptions`.`product_id` in (846,845,844,832,829,828,822,817,816,662,814,806,805,804,803,802,801,800,799,798,797,796,795,792,787,786,782,819,781,765,764,763,762,760,758,752,751,750,749,747,744,743,742,741,732,731,727,725,724,723,809,810,720,718,717,716,715,713,709,708,707,705,701,697,696,695,693,682,676,673,671,670,664,663,658,657,656,651,650,647,645,644,641,639,636,624,622,620,619,618,616,615,608,607,600,597)) and (`betaatif_store`.`cscart_product_descriptions`.`lang_code` = 'en'))",
      "cost_info": {
        "read_cost": "57.61",
        "eval_cost": "9.60",
        "prefix_cost": "67.21",
        "data_read_per_join": "366K"
      },
      "used_columns": [
        "product_id",
        "lang_code",
        "short_description",
        "full_description"
      ]
    }
  }
}