Validating super/sub entity relationships, 3.1M3 vs. 3.0.2

[Robert Zeigler <ro...@roxanemy.com>]

I'm gradually migrating my projects to 3.1M3 from the 3.0 series. Today, I converted a project in the modeler and it now complains:

"Usage of super entity's relationships 'Entry.user' as reversed relationships for sub entity is discouraged"

I'm using single-table inheritance in this case, and "Entry" is the superclass, with two sub-classes. Every subclass needs a reference to the "user" table, so I put the relationship in the superclass rather than the subclasses. So my questions:

1) Why is this discouraged?
  1b) What are the side-effects of maintaining the current mapping?
2) I suppose the "correct" thing is to remap this as one relationship to the user table for each subclass?
3) What change in behavior from 3.0.2 -> 3.1M3 warrants this new warning/preference? Or has it always been bad practice but now we're letting people know?

Robert

Re: Validating super/sub entity relationships, 3.1M3 vs. 3.0.2

[Robert Zeigler <ro...@roxanemy.com>]

That would definitely help. 

Robert

On Mar 27, 2012, at 3/272:55 AM , Andrus Adamchik wrote:

>> That said, the warning was pointing to the Entry entity, but I think the bad mapping was in the User entity. Maybe it's a matter of perspective? Or is that a bug?
> 
> From the top of my head, Cayenne detects a cycle in relationship joins, but it can't tell which relationship in the pair a user might prefer to change (e.g. a relationship may only be relevant in subclass). So it takes a random guess. We should probably improve the error message to mention both relationships are candidates for refactoring.
> 
> Andrus
> 
> 
> On Mar 27, 2012, at 12:48 AM, Robert Zeigler wrote:
> 
>> After examining my project some more, I found the offending relationship.
>> 
>> I have (generically):
>> Entry (to one)-> User
>> EntryType1 -> user (inherited from Entry)
>> EntryType2 -> user (inherited from Entry)
>> 
>> And:
>> User (to many) => EntryType1
>> 
>> The offending relationship was the User => EntryType1. Once I changed that to User => Entry, the project validated fine.
>> This makes sense: having User -> Entry and Entry -> User makes more sense than User -> EntryType1 and Entry -> User. The "bad" mapping is an artifact of having refactored the class hierarchy awhile ago.
>> 
>> That said, the warning was pointing to the Entry entity, but I think the bad mapping was in the User entity. Maybe it's a matter of perspective? Or is that a bug?
>> 
>> Robert
>> 
>> On Mar 26, 2012, at 3/264:41 PM , Robert Zeigler wrote:
>> 
>>> I'm gradually migrating my projects to 3.1M3 from the 3.0 series. Today, I converted a project in the modeler and it now complains:
>>> 
>>> "Usage of super entity's relationships 'Entry.user' as reversed relationships for sub entity is discouraged"
>>> 
>>> I'm using single-table inheritance in this case, and "Entry" is the superclass, with two sub-classes. Every subclass needs a reference to the "user" table, so I put the relationship in the superclass rather than the subclasses. So my questions:
>>> 
>>> 1) Why is this discouraged?
>>> 1b) What are the side-effects of maintaining the current mapping?
>>> 2) I suppose the "correct" thing is to remap this as one relationship to the user table for each subclass?
>>> 3) What change in behavior from 3.0.2 -> 3.1M3 warrants this new warning/preference? Or has it always been bad practice but now we're letting people know?
>>> 
>>> Robert
>> 
>> 
> 

Re: Validating super/sub entity relationships, 3.1M3 vs. 3.0.2

[Andrus Adamchik <an...@objectstyle.org>]

> That said, the warning was pointing to the Entry entity, but I think the bad mapping was in the User entity. Maybe it's a matter of perspective? Or is that a bug?

From the top of my head, Cayenne detects a cycle in relationship joins, but it can't tell which relationship in the pair a user might prefer to change (e.g. a relationship may only be relevant in subclass). So it takes a random guess. We should probably improve the error message to mention both relationships are candidates for refactoring.

Andrus


On Mar 27, 2012, at 12:48 AM, Robert Zeigler wrote:

> After examining my project some more, I found the offending relationship.
> 
> I have (generically):
> Entry (to one)-> User
>  EntryType1 -> user (inherited from Entry)
>  EntryType2 -> user (inherited from Entry)
> 
> And:
>  User (to many) => EntryType1
> 
> The offending relationship was the User => EntryType1. Once I changed that to User => Entry, the project validated fine.
> This makes sense: having User -> Entry and Entry -> User makes more sense than User -> EntryType1 and Entry -> User. The "bad" mapping is an artifact of having refactored the class hierarchy awhile ago.
> 
> That said, the warning was pointing to the Entry entity, but I think the bad mapping was in the User entity. Maybe it's a matter of perspective? Or is that a bug?
> 
> Robert
> 
> On Mar 26, 2012, at 3/264:41 PM , Robert Zeigler wrote:
> 
>> I'm gradually migrating my projects to 3.1M3 from the 3.0 series. Today, I converted a project in the modeler and it now complains:
>> 
>> "Usage of super entity's relationships 'Entry.user' as reversed relationships for sub entity is discouraged"
>> 
>> I'm using single-table inheritance in this case, and "Entry" is the superclass, with two sub-classes. Every subclass needs a reference to the "user" table, so I put the relationship in the superclass rather than the subclasses. So my questions:
>> 
>> 1) Why is this discouraged?
>> 1b) What are the side-effects of maintaining the current mapping?
>> 2) I suppose the "correct" thing is to remap this as one relationship to the user table for each subclass?
>> 3) What change in behavior from 3.0.2 -> 3.1M3 warrants this new warning/preference? Or has it always been bad practice but now we're letting people know?
>> 
>> Robert
> 
> 

Re: Validating super/sub entity relationships, 3.1M3 vs. 3.0.2

[Robert Zeigler <ro...@roxanemy.com>]

After examining my project some more, I found the offending relationship.

I have (generically):
Entry (to one)-> User
  EntryType1 -> user (inherited from Entry)
  EntryType2 -> user (inherited from Entry)

And:
  User (to many) => EntryType1

The offending relationship was the User => EntryType1. Once I changed that to User => Entry, the project validated fine.
This makes sense: having User -> Entry and Entry -> User makes more sense than User -> EntryType1 and Entry -> User. The "bad" mapping is an artifact of having refactored the class hierarchy awhile ago.

That said, the warning was pointing to the Entry entity, but I think the bad mapping was in the User entity. Maybe it's a matter of perspective? Or is that a bug?

Robert

On Mar 26, 2012, at 3/264:41 PM , Robert Zeigler wrote:

> I'm gradually migrating my projects to 3.1M3 from the 3.0 series. Today, I converted a project in the modeler and it now complains:
> 
> "Usage of super entity's relationships 'Entry.user' as reversed relationships for sub entity is discouraged"
> 
> I'm using single-table inheritance in this case, and "Entry" is the superclass, with two sub-classes. Every subclass needs a reference to the "user" table, so I put the relationship in the superclass rather than the subclasses. So my questions:
> 
> 1) Why is this discouraged?
>  1b) What are the side-effects of maintaining the current mapping?
> 2) I suppose the "correct" thing is to remap this as one relationship to the user table for each subclass?
> 3) What change in behavior from 3.0.2 -> 3.1M3 warrants this new warning/preference? Or has it always been bad practice but now we're letting people know?
> 
> Robert