Instead of having each line as a child context under a parent context, parent - child1 (line 1) - child2 (line 2) - child3 (line 3)
could you have each line processed as a child context of the previous line? - child1 (line 1) -- child2 (line 2) --- child3 (line 3) ---- child4 (line 4) If you want to "undo" the current line, child4.rollbackChangesLocally(); and start on the next line. Note that I have not done anything with child contexts, but this would be how I'd try to solve it. On Wed, Mar 28, 2018 at 9:29 PM, Ken Anderson <k...@anderhome.com> wrote: > Hugi, > > That’s correct - it’s not like we’re just importing a bunch of records. Each > row in the file could affect the same set of objects. > > So, we did the child context, but obviously if we created an object in a > prior child and then saved it to the parent, we won’t be able to easily find > it in the next child context. If you get a localObject in your new child > context, it is “hollow”, so not connected to all the other objects floating > around in the parent. We also can’t fire relationships, because those > relationships will go to the database instead of the parent context. > > Ken > >> On Mar 28, 2018, at 7:11 PM, Hugi Thordarson <h...@karlmenn.is> wrote: >> >>> That's exactly what we want to do - save once at the end. However, we have >>> 2 problems: >>> >>> 1. How do we find the objects that we already created but haven't saved yet >> >> You can go through yur ObjectContext's newObjects() and filter that to your >> liking—pretty much the same as you'd do with EOF. >> >>> 2. How do we roll back each line if there's an error? Not a DB error, but >>> the logic gets so far, and then determines that there's no way to continue >>> so we must skip this line. >> >> As you tried yourself, I'd use a child context and commit to the parent once >> you're sure everything is in place. Can you explain further what was >> problematic with that (that you need to "access the same objects multiple >> times")? Do you mean that each row of the file is in some way looking at >> data from other rows? >> >> Cheers, >> - hugi >> >> >>> >>> Ken >>> >>> On 3/28/18, 6:07 PM, "John Huss" <johnth...@gmail.com> wrote: >>> >>> Well, you could just save once at the end. Why do you need to save >>> multiple times during the processing? Validation exceptions and >>> Optimistic >>> Locking errors could be handled in the save with some custom logic and a >>> retry. >>> >>> Or if this isn't a super long process you can use a database transaction >>> to >>> allow saving multiple times without actually having that data be visible >>> outside of the transaction. >>> >>> >>> On Wed, Mar 28, 2018 at 6:56 AM Ken Anderson <ken.ander...@amphorainc.com> >>> wrote: >>> >>>> All, >>>> >>>> We have a process that reads in a file and, for each line, creates or >>>> edits objects in the object graph. We only want to commit to the database >>>> once at the end. >>>> >>>> We have a finite set of lines, so memory is not an issue. We need to save >>>> only once because saving will actually fire triggers that will start doing >>>> other things to the database, which will then lead to optimistic lock >>>> exceptions for us if we have data that overlaps (which we do). >>>> >>>> Please don’t suggest we change how the trigger pattern works – it’s a big >>>> system and we don’t have control over it. >>>> >>>> So, what we’ve toyed with is using a parent/child context arrangement, >>>> where each line is processed in a child, and assuming everything goes OK, >>>> we commit only to the parent. This works well as long as we don’t need to >>>> access the same objects multiple times, but unfortunately, we do. We can >>>> reach into the parent context’s unsaved objects, but those objects do not >>>> have any relationships since they were built in the child context. This >>>> makes things painful. >>>> >>>> In EOF, I might consider using a single context and undo, but it doesn’t >>>> seem like Cayenne has this kind of functionality. >>>> >>>> Thoughts? Suggestions? In EOF, I had once written a layer that >>>> intercepted all queries and tried to find the correct object in unsaved >>>> objects, but I don’t have nearly enough experience with Cayenne to do that. >>>> >>>> Thanks! >>>> Ken >>>> >>>> Confidentiality Notice: This e-mail and accompanying documents contain >>>> confidential information intended for a specific individual and purpose. >>>> This e-mailed information is private and protected by law. If you are not >>>> the intended recipient, you are hereby notified that any disclosure, >>>> copying, or distribution, or the taking of any action based on the contents >>>> of this information, is strictly prohibited. >>>> >>> >>> >>> Confidentiality Notice: This e-mail and accompanying documents contain >>> confidential information intended for a specific individual and purpose. >>> This e-mailed information is private and protected by law. If you are not >>> the intended recipient, you are hereby notified that any disclosure, >>> copying, or distribution, or the taking of any action based on the contents >>> of this information, is strictly prohibited. >> >
