Question

I’m struggling with a performance issue for a copy feature that my application provides to the users. I’m not sure I’m going about it the right way. I don’t have a lot of experience in Hibernate.

An over-simplified layout would be:

Project ---> (One to Many) Items ---> (One to Many) Tasks
Project ---> (One to Many) Variables
Items <---> Variables (Many to Many)

So, a project can have many items, and each item can have many tasks. A project can have variables (no duplicates), and there is a many to many between items and variables (they are attached to one another).

There could be several hundred items per project, with several (20-30) tasks per item, and several hundred variables per project. I added a function that allows users to check which items and tasks they want to copy from one project to another. There cannot be any duplicates.

Here’s the process I perform for each item that is checked:

1. Check to see if the item exists in the target project, if it does, add it, otherwise, don’t. I used the session.createFilter to query the target project (by item name). If the item does not exist, I add it. (object.save()), and add it to the target project’s items collection.
2. If the item has variables attached to it, I check the target project for those variables (again session.createFilter()), add them if they are not there, then add them to the item.variables collection

I’m not sure what, if anything, I can do to speed this up. I’m assuming doing all the checks first isn’t helping things. I don’t know if the createFilter is the best way for checking that items/variables exist in the target project.

I’ve tried changing the way the objects are added to collections. I would add them each one at a time (targetProject.add(item)), now I’m storing them in an arraylist and when all items are iterated through, I then do a targetProject.addAll(items). I couldn’t tell a difference, though.

Is there a better way of doing this? I’m using Ehcache as a second-level caching. I’m also still on Hibernate 3.2.5.

Any help is appreciated.

Answer 1

It looks like your code issues too many database queries due to frequent use of createFilter().

It would be better to fetch all needed objects into memory by a few queries, and then perform necessary checks using appropriate in-memory data structures (Maps, Sets).