SELECT 
  product_descriptions.product_id, 
  product_descriptions.short_description, 
  IF(
    product_descriptions.short_description = '' 
    OR product_descriptions.short_description IS NULL, 
    product_descriptions.full_description, 
    ''
  ) AS full_description 
FROM 
  product_descriptions 
WHERE 
  product_descriptions.product_id IN (
    138903, 171934, 139416, 139364, 139389, 
    139360, 138902, 139368, 173441, 139376, 
    139318, 139415, 139314, 139315, 139377, 
    149277, 139381, 139366, 139363, 139387, 
    139379, 139418, 139321, 139361, 139419, 
    173429, 149275, 139380, 139355, 139358, 
    139372, 139383, 139390, 138901, 173431, 
    173432, 149249, 173426, 138899, 173436, 
    149261, 149274, 139370, 173443, 139367, 
    173438, 139385, 149278
  ) 
  AND product_descriptions.lang_code = 'en'

Query time 0.00272

JSON explain

{
  "query_block": {
    "select_id": 1,
    "cost_info": {
      "query_cost": "39.75"
    },
    "table": {
      "table_name": "product_descriptions",
      "access_type": "range",
      "possible_keys": [
        "PRIMARY",
        "product_id"
      ],
      "key": "PRIMARY",
      "used_key_parts": [
        "product_id",
        "lang_code"
      ],
      "key_length": "11",
      "rows_examined_per_scan": 48,
      "rows_produced_per_join": 48,
      "filtered": "100.00",
      "cost_info": {
        "read_cost": "34.95",
        "eval_cost": "4.80",
        "prefix_cost": "39.75",
        "data_read_per_join": "244K"
      },
      "used_columns": [
        "product_id",
        "lang_code",
        "short_description",
        "full_description"
      ],
      "attached_condition": "((`goimagine`.`product_descriptions`.`product_id` in (138903,171934,139416,139364,139389,139360,138902,139368,173441,139376,139318,139415,139314,139315,139377,149277,139381,139366,139363,139387,139379,139418,139321,139361,139419,173429,149275,139380,139355,139358,139372,139383,139390,138901,173431,173432,149249,173426,138899,173436,149261,149274,139370,173443,139367,173438,139385,149278)) and (`goimagine`.`product_descriptions`.`lang_code` = 'en'))"
    }
  }
}