Re: Business layer cleanup for 3.2

[Craig L Russell]

Hi Allen,

On Nov 14, 2006, at 9:06 AM, Allen Gilliland wrote:

Dave wrote:

On 11/13/06, Allen Gilliland <[EMAIL PROTECTED]> wrote:

One of the things that I am planning to do for the 3.2 release is do
some audit/cleanup of the current business layer code.  There are a

associations.

variety of things which could use improving, but the main goal is to fix our Hibernate configuration so that we are 1) properly using the open session in view pattern and 2) enabling lazy fetching on all objects and

All good.

Right now our Hibernate config is pretty messy and doesn't take
advantage of many of Hibernate's performance features, so the main
reason to do this work is to improve the performance of the business

so those would all be cleaned up.

I have most of this work done already (but not checked in) and there
aren't really any surprise changes that I had to make except when it

current data model, but I kept running into problems.  So to fix the

HierarchicalPersistentObject class and Assoc and it's subclasses and


So, for weblog categories I added a simple 'parentid' column to the

only requires populating these columns with the right value.

layer. The second big reason is just to reduce clutter and simplify the code as much as possible. There are plenty of places in the code where we have methods that aren't used at all or methods which are duplicated, came to the hierarchical objects. I tried for multiple days to get the hierarchical objects to work with the updated hibernate config and the problem I had to make a small tweak to the way hierarchical objects are persisted which fixed my issues and I believe drastically simplifies the problem overall. The basic change is that I have completely removed the changed the data model so that we have a more normal hierarchical model. weblogcategory table and that allows a category to manage relationships between it's parent and children directly. Same goes for the FolderData class, but as it turns out that column already existed in the schema but wasn't being used. Upgrade path for both of these is fairly simple and

The hierarchical persistent object and the assoc tables were there for

one purpose: to make it possible to do a recursive query (i.e. query

one SQL statement. But that hasn't worked since we made the switch to
the Hibernate Criteria API back in 2004 and we've been doing fine

so much that now it's almost unintelligible.
So I'm +1 with that change.

for all entries under /pets and /pets/dogs, /pets/cats etc.) with only without it. And the code that started as complex has been moved around

Actually, I have an idea that I think can accomplish what's described above and actually kill a couple other birds with the same stone. Basically, if we add another column for the full path of a node like you did above (/pets, /pets/dogs, /pets/cats) then to get all entries under the category /pets by getting all entries that have a category with a path that starts with "/pets". So the sql query would just be ... select * from weblogentry,weblogcategory where weblogentry.categoryid = weblogcategory.id and weblogcategory.path like '/pets%'; This would also significantly improve the current performance of the getPath() methods on our hierarchical objects because it would be a simple attribute instead of needing to be calculated at runtime. And this would also be much better for implementing equals () on these objects since the true key for a hierarchical object is it's path. The only down side is that the migration path for that would require walking the category and folder trees for all weblogs and saving the path for all of them, which is fairly complex :/

It seems to me that this is a tradeoff between simplicity and performance. Simplicity is storing the local path name and a reference to the parent; performance is storing the entire path.

Craig

Performance seems to be the better tradeoff here. Operations like moving or renaming a path require recursively changing the entire path of all children but I assume that the performance benefits outweigh the complexity of these infrequent operations.

-- Allen

- Dave

Craig Russell
Architect, Sun Java Enterprise System http://java.sun.com/products/jdo
408 276-5638 mailto:[EMAIL PROTECTED]
P.S. A good JDO? O, Gasp!

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