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 (
    49682, 49547, 49130, 49124, 50045, 49015, 
    49800, 49759, 49737, 49734, 49736, 
    50195, 49209, 49662, 50303, 50134, 
    50135, 50300, 50316, 49785, 50297, 
    49937, 50299, 50298, 50278, 49214, 
    50235, 50218, 49788, 50287, 50305, 
    50286
  ) 
  AND cscart_product_descriptions.lang_code = 'en'

Query time 0.01157

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": 32,
          "filtered": 100,
          "index_condition": "cscart_product_descriptions.product_id in (49682,49547,49130,49124,50045,49015,49800,49759,49737,49734,49736,50195,49209,49662,50303,50134,50135,50300,50316,49785,50297,49937,50299,50298,50278,49214,50235,50218,49788,50287,50305,50286) and cscart_product_descriptions.lang_code = 'en'"
        }
      }
    ]
  }
}