Re: [dali-dev] JPQL query generation?

[Tom Mutdosch <tommut@xxxxxxxxxxx>]

Hi Shaun,

Thanks for the feedback.  You've certainly convinced me of the virtues of 
object-based JPQL queries :)  It sounds as if I definitely want to avoid SQL 
queries if there's no real reason to use them.

That said, when you mentioned JPQL support is on the feature backlog for the 
future; do you think that support would likely entail some sort of query 
builder, or something along those lines?

Thanks
Tom

Shaun Smith wrote:
> Hi Tom,
>
>
> There isn't a visual query builder in Dali but JPQL support is on the 
> feature backlog.
>
> I really wouldn't recommend SQL queries. They're there as a last resort. 
> You lose a number of advantages of JPA including encapsulation of the 
> data model. You'll be coupling your code (queries) to the data model. 
> Coupling should be limited to your mappings. Mappings can adapt to data 
> model changes (and Dali will detect them), and your queries can continue 
> to work without change since you're querying on the object model. Also, 
> JPA persistence providers parse JPQL and can do things like avoid 
> database round trips by using a cache. A primary key query is an obvious 
> one. If what you want is in the cache and you know it's reliable why go 
> to the database? When using SQL your provider will just pass it along 
> and process the results so you lower the value of the cache. The big 
> issue IMHO is the unnecessary coupling of queries to the data model and 
> the brittleness it introduces. I've seen database migrations from DB/2 
> to Oracle of two applications in a workflow, one using TopLink, one 
> using direct SQL. The SQL based application was way more expensive to 
> port. They had to go over every line of SQL whereas the TopLink based 
> application required the mappings adjusted (minimally I might add) and 
> the application ran. Theory is nice but seeing it play out in real life 
> made the advantage of object based queries concrete.
>
>    Shaun