Java-Spring-Hibernate从数据库中提取1000个对象需要很长时间

Question

I have a Postgres database with 17 tables create by Hibernate with the @Entity annotation and iam running CrudRepository with the findAll method for extracting objects from the database

Everything works fine until I try to retrieve 1000 + objects from the database which takes 27 seconds. Retrieving 600 objects takes around 10 seconds.

The time is increasing exponentially and I am wondering if there is a solution to this, I know that if I try to join tables it would speed up the process but joining tables on 17 tables is a lot of work. Are there other extracting methods that are faster on retrieving objects besides the one that I am using?

This is how I retrieve objects:

public List<Document> getAllDatabaseDocuments() {
    List<Document> listOfDocs = new ArrayList<>();
    listOfDocs.addAll((List<Document>) sdr.findAll());
    return listOfDocs;
}

Answer 1

All JPA providers have QueryHints to do certain query optimization. It provides you with the ability to fetch all associations in a single query or using joins. For example, In EclipseLink, you can use QueryHints.BATCH to fetch all one to many or many to many associations in a single query.

Instead of using findAll() , create your own query in your entity and provide the appropriate query hint specific to hibernate. join-fetch in your case will take a lot of time because you have a lot of related entities. Try to use batch-fetch as it will reduce the number of queries and effectively speeds up the fetching.

You can learn more about hibernate specific fetching strategies here