Re: lazy materialization problem
I'm using 1.0.3 version and default (per broker) cache yes persistence broker wich fetch folder is different from that one wich materialize children. So to prevent this I need touch all objects in single persistence broker (long-lived caches dont feet me because I'm using web application with many clients). But I think its not good to iterate over the whole folder tree and touch every object because every touch is call to database. If I cauld say OJB prefetch parent and children reference in all folders wich I materizalize by this call it would be more productive Clute, Andrew wrote: What version of OJB are you using (1.0, 1.0.2?), and which type of cache are you using? (ObjectCacheTwoLevel, ObjectCacheDefaultImpl)? The issue stems from the fact that your proxy collection is being materialized with 1) a different PersistneceBroker instance then the parent object, and 2) You are using a cache implementation that either creates copies (ObjectCacheTwoLevel) or is short-lived (ObjectCachePerBroker). This is a known issue, especially with all the cache implementations other than ObjectCacheDefault. For instance, if you are using ObjectCacheTwoLevel, it guarantees detached objects from the application cache, while guaranteeing the same reference for logically identical objects, but only for the life of the PersistenceBroker. So, if the parent object is created in one PB instance, and the collection proxy is materialized in another PB instance, you will get different references for your 'folder' object. Can you tell me a little bit more about your application: Is this a web app? What is the lifecycle for your PersistenceBrokers (do you use one for each action? Keep one open for the entire request?). Does the materlization of our parent 'folder' object happen in the same request as when the collection proxy is 'touched' and forced to be materialized? -Andrew - To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
RE: lazy materialization problem
If I cauld say OJB prefetch parent and children reference in all folders wich I materizalize by this call it would be more productive I am slightly confused by this statement. Are you saying you want all the children to be materialized when the parent is created, thus populating all of the children's back-references to it's parent with the same instance? If so, how is what you are asking for different than just setting the collection of children not to be a proxy collection? The problem you are experiencing is something that we would like to fix, so I would love to hear any, and all suggestions on work arounds for it. But I am having trouble understanding what exactly your solution is. On a side note: One quick, dirty, workaround is to save your 'folder' object inside the new PersistenceBroker before calling any method on the children collection to make it be materizalized. This will 1) save the object to the DB, but 2) Place that object in the cache, so the same reference will be used for your back-references. Now, this might not work in your scenario, especially if your 'folder' object has been mutated, and you are not ready to persist it yet. However, just a thought. -Andrew - To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
Re: lazy materialization problem
Clute, Andrew wrote: If I cauld say OJB prefetch parent and children reference in all folders wich I materizalize by this call it would be more productive I am slightly confused by this statement. Are you saying you want all the children to be materialized when the parent is created, thus populating all of the children's back-references to it's parent with the same instance? yes! That what I want. In many cases proxies are well. In 99% i load only one folder, somethimes view its children or parent. So this problem in 99% doesn't bother me. But only for one particular case I need work with the whole tree. So I want to change proxy attribute only for for this case when I want load the whole folders tree. Is it possible? On a side note: One quick, dirty, workaround is to save your 'folder' object inside the new PersistenceBroker before calling any method on the children collection to make it be materizalized. This will 1) save the object to the DB, but 2) Place that object in the cache, so the same reference will be used for your back-references. Now, this might not work in your scenario, especially if your 'folder' object has been mutated, and you are not ready to persist it yet. However, just a thought. -Andrew - To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
RE: lazy materialization problem
If I cauld say OJB prefetch parent and children reference in all folders wich I materizalize by this call it would be more productive I am slightly confused by this statement. Are you saying you want all the children to be materialized when the parent is created, thus populating all of the children's back-references to it's parent with the same instance? yes! That what I want. In many cases proxies are well. In 99% i load only one folder, somethimes view its children or parent. So this problem in 99% doesn't bother me. But only for one particular case I need work with the whole tree. So I want to change proxy attribute only for for this case when I want load the whole folders tree. Is it possible? Yeah, take a look at: http://db.apache.org/ojb/docu/guides/metadata.html#Per+thread+metadata+c hanges The basic concept is that you can get a copy of the DescriptorRepository, and then get the ClassDescriptor for your 'folder' object, and then get the CollectionDescriptor for your 'children' collection. Then CollectionDescriptor#setLazy(false) for the duration of your call, and then set it back. Make sure to read about doing MetaData changes per Thread -- otherwise your changes will affect the entire application, and not just this particular instance (all instance of that collection will be loaded, not just the one you care about). Hope this helps. -Andrew - To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
Re: lazy materialization problem
Thanks Andrew! That's what I need ;) If I cauld say OJB prefetch parent and children reference in all folders wich I materizalize by this call it would be more productive I am slightly confused by this statement. Are you saying you want all the children to be materialized when the parent is created, thus populating all of the children's back-references to it's parent with the same instance? yes! That what I want. In many cases proxies are well. In 99% i load only one folder, somethimes view its children or parent. So this problem in 99% doesn't bother me. But only for one particular case I need work with the whole tree. So I want to change proxy attribute only for for this case when I want load the whole folders tree. Is it possible? Yeah, take a look at: http://db.apache.org/ojb/docu/guides/metadata.html#Per+thread+metadata+c hanges The basic concept is that you can get a copy of the DescriptorRepository, and then get the ClassDescriptor for your 'folder' object, and then get the CollectionDescriptor for your 'children' collection. Then CollectionDescriptor#setLazy(false) for the duration of your call, and then set it back. Make sure to read about doing MetaData changes per Thread -- otherwise your changes will affect the entire application, and not just this particular instance (all instance of that collection will be loaded, not just the one you care about). Hope this helps. -Andrew - To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED] - To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
Re: lazy materialization problem
Maksimenko Alexander wrote: I have tree like structure (with parent,children relationships). I'm using proxies to lazy materialize them. Everything works well but in particular cases I have to materialize the whole tree because folder.getChildren().get(0).getParent() is not the same as folder and sometimes it makes the problem. How can I tell OJB to prefetch references parent and children for all folders? Or is there simpler way to do this? I am not sure I understand your question correctly, but it sounds like you (possibly among other things) are interested in getting a deterministic order on your Collection references? If that is the case, have a look at the orderby and sort attributes of collection-descriptor [1]. If your problem is that from child=parent you don't get the 1:1 mapping you would like, could you please tell us the details of your repository file? I guess from your text that you want: a) for parent class, to map children with collection-descriptor and inverse FK b) for child class, to map parent with reference-descriptor and FK On a, ie parent=child and Collection, you might want to use an ordered collection as collection class and set orderby and sort attributes in order to get deterministic ordering of the collection (if not, you will get RDBMS ordering = random and likely to change on insert/update/delete on the table even if you use an ordered Java collection as collection-class). Please get back with more details if I didn't understand your question. Regards, Martin [1] http://db.apache.org/ojb/docu/guides/repository.html#collection-descriptor-N10611 - To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
Re: lazy materialization problem
Martin Kalén wrote: Maksimenko Alexander wrote: I have tree like structure (with parent,children relationships). I'm using proxies to lazy materialize them. Everything works well but in particular cases I have to materialize the whole tree because folder.getChildren().get(0).getParent() is not the same as folder and sometimes it makes the problem. How can I tell OJB to prefetch references parent and children for all folders? Or is there simpler way to do this? I am not sure I understand your question correctly, but it sounds like you (possibly among other things) are interested in getting a deterministic order on your Collection references? If that is the case, have a look at the orderby and sort attributes of collection-descriptor [1]. Sory a was not clear enough :( No I mean that due lazy initialization folder and folder.getChildren().get(0).getParent() are equals (by id) but not the same objects. Lets we have Folder folder = ...//get from ojb Folder child = folder.getChildren().get(0); folder.changeName(new-name) // but child.getParent().getName() doesn't equal new-name its okey in the most cases but in only one case I need prevent this. I think this problem will disapear if I can tell ojb don't use proxies for particular getting objects from database. but I don't know how I can do this Hope I was clear now ;) Thanks Alexander - To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
RE: lazy materialization problem
What version of OJB are you using (1.0, 1.0.2?), and which type of cache are you using? (ObjectCacheTwoLevel, ObjectCacheDefaultImpl)? The issue stems from the fact that your proxy collection is being materialized with 1) a different PersistneceBroker instance then the parent object, and 2) You are using a cache implementation that either creates copies (ObjectCacheTwoLevel) or is short-lived (ObjectCachePerBroker). This is a known issue, especially with all the cache implementations other than ObjectCacheDefault. For instance, if you are using ObjectCacheTwoLevel, it guarantees detached objects from the application cache, while guaranteeing the same reference for logically identical objects, but only for the life of the PersistenceBroker. So, if the parent object is created in one PB instance, and the collection proxy is materialized in another PB instance, you will get different references for your 'folder' object. Can you tell me a little bit more about your application: Is this a web app? What is the lifecycle for your PersistenceBrokers (do you use one for each action? Keep one open for the entire request?). Does the materlization of our parent 'folder' object happen in the same request as when the collection proxy is 'touched' and forced to be materialized? -Andrew -Original Message- From: Maksimenko Alexander [mailto:[EMAIL PROTECTED] Sent: Thursday, April 28, 2005 8:03 AM To: OJB Users List Subject: Re: lazy materialization problem Martin Kalén wrote: Maksimenko Alexander wrote: I have tree like structure (with parent,children relationships). I'm using proxies to lazy materialize them. Everything works well but in particular cases I have to materialize the whole tree because folder.getChildren().get(0).getParent() is not the same as folder and sometimes it makes the problem. How can I tell OJB to prefetch references parent and children for all folders? Or is there simpler way to do this? I am not sure I understand your question correctly, but it sounds like you (possibly among other things) are interested in getting a deterministic order on your Collection references? If that is the case, have a look at the orderby and sort attributes of collection-descriptor [1]. Sory a was not clear enough :( No I mean that due lazy initialization folder and folder.getChildren().get(0).getParent() are equals (by id) but not the same objects. Lets we have Folder folder = ...//get from ojb Folder child = folder.getChildren().get(0); folder.changeName(new-name) // but child.getParent().getName() doesn't equal new-name its okey in the most cases but in only one case I need prevent this. I think this problem will disapear if I can tell ojb don't use proxies for particular getting objects from database. but I don't know how I can do this Hope I was clear now ;) Thanks Alexander - To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED] - To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
lazy materialization problem
Hi! I have tree like structure (with parent,children relationships). I'm using proxies to lazy materialize them. Everything works well but in particular cases I have to materialize the whole tree because folder.getChildren().get(0).getParent() is not the same as folder and sometimes it makes the problem. How can I tell OJB to prefetch references parent and children for all folders? Or is there simpler way to do this? Thanks. Alexander - To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
