Hibernate（HQL）查找缺少的参数列表ID

Question

Let's assume i have a list of ids (as parameter, not a table) and a table with entities and their ids.

Parameter list: ids: 1,2,3,4

Table-Entities: ids: 1,3,4

Now i want to find all missing values of my parameter list, that are not stored in the database, in this case: id 2.

The simple and overloaded function i have in mind is to query every single id for existence... and add it to a result if it does not exists.

public List<long> findMissing(List<long> ids) {
    List<long> missing = new ArrayList<long>();
    for (long id : ids) {
         if (!dao.exists(id))
              missing.add(id);
    }
    return missing;
}

... but i think that this is a bad idea, if the list grows (we are talking about 0 - 1000 elements).

I'm wondering if there is a HQL function like this:

SELECT t FROM (:ids) t 
     WHERE t not in 
          (SELECT e.id FROM MyEntity e 
               WHERE *maybe some conditions*);

Answer 1

Unfortunately, parameters are not allowed in the FROM clause. You will need to select all the ids and filter them in-memory. This shouldn't be too costly for 0-1000 elements.