Optimize retrieves in expressions
In general, I recommend to never execute retrieves in expressions. The example below, a customer is linked 1-1 with an address. It may seem like an innocent create variable, but actually does a data retrieve over association:
- If you do have the address in cache ('dirty state'), then you can consider it as an 'innocent' setting a variable. Still, for better maintainability I would recommend to explicitly retrieve over association in the step before, such that is visible what's happening and no retrievals are hidden.
- If you don't have the address in cache, then not only the street is retrieved from database, but all attributes and even associations where the Address entity is owner of will be retrieved, while Studio Pro knows exactly that only the Street attribute is used. If you use the same object again (in the same activity or another), then you will also end up with bad performance, as the retrieval will be done multiple times.
So mainly for maintainability, but also for performance reasons I would love to see this changed in Studio Pro.
Possible solutions:
- Don't allow to do retrievals in the expression editor at all (probably difficult to implement by now)
- Make this a performance-optimized feature by only retrieving the explicit mentioned attribute.
Thanks for your vote!
In general this feature was wanted some time ago and I recall colleagues wanting this. The implementation is highly flawed though. In its current implementation it creates a mess; hidden logic and unexpected performance loss.
In hindsight this should be removed, so I agree
Currently if you use the same object twice in an expression, Mendix will retrieve the object twice, so that means the performance is even worse than Johan's proposal. If you want to use multiple attributes in 1 expression: first retrieve the object, then create the expression based on the variable.
I agree with you Johan.
If we use only one attribute in expressions, it is fine.
But what if when we use same entity with multiple attributes different times, then retrieving every time single attribute will definitely causes performance issues. Doesn't it?