Re: [Hibernate] questions about polymorphism
>> It seems that if I use "table-per-class", I am going to get hit with thirty queries every time I do a select of the superclass, is that correct? << Correct >> But if I use "table-per-subclass" with , I will get two selects -- one for the superclass result set and one for each table (or table type) that exists in the result set. << No, Hibernate uses a great big outer join, because there is no discriminator column in joined-subclass mappings. The subclass fetching strategy you just described (we need to give it a name) is subject to the N+1 selects problem. However, I *do* plan to support it in a not too distant future version. (Hibernate 2.1.1 perhaps.) Actually, It will be a variation of the proposed multi-table mapping support, ie. the mapping. For multitable mappings we will support both and . So the fetching strategy you describe would be implementable as B and C in the following: So we now have a fully mixed inheritance strategy!! This hierarchy combines together a table-per-subclass loaded by joining, 2 table-per-subclasses loaded by sequential read and another subclass mapped to the superclass table. Don't expect this stuff in the next two weeks, however! >> Since the subclass is completely described this way, is the separate mapping file for the subclass redundant? << You should not have a seperate mapping file for a subclass. |-+---> | | "Brian Topping" | | | <[EMAIL PROTECTED]> | | | Sent by:| | | [EMAIL PROTECTED]| | | ceforge.net | | | | | | | | | 07/08/03 04:19 PM | | | | |-+---> >--| | | | To: <[EMAIL PROTECTED]> | | cc: | | Subject: [Hibernate] questions about polymorphism | >--| Hi all, I have some questions about polymorphic persistence. Any takers? I have a schema that currently has about thirty subclasses (more with time) and one common superclass. I am looking for polymorphism between these subclasses. It seems that if I use "table-per-class", I am going to get hit with thirty queries every time I do a select of the superclass, is that correct? But if I use "table-per-subclass" with , I will get two selects -- one for the superclass result set and one for each table (or table type) that exists in the result set. Since most of the collections are of a single subtype, this seems to be the most efficient. True? [a comment: adding a "WildCat" subclass to the documentation example next to "DomesticCat" would be helpful, although it may add unnecessary complexity to the single page manual, since there are no examples of having multiple subclasses with a common parent.] Finally, if I understand the mapping file schema correctly, the superclass mapping file is going to be very very large, essentially containing all of the subclasses in entities. Since the subclass is completely described this way, is the separate mapping file for the subclass redundant? Thanks for any thoughts!! Brian --- This SF.Net email sponsored by: Free pre-built ASP.NET sites including Data Reports, E-commerce, Portals, and Forums are available now. Download today and enter to win an XBOX or Visual Studio .NET. http://aspnet.click-url.com/go/psa0013ave/direct;at.aspnet_072303_01/01 ___ hibernate-devel mailing list [EMAIL PROTECTED] https://lists.sourceforge.net/lists/listinfo/hibernate-devel ** Any personal or sensitive information contained in this email and attachments must be handled in accordance with the Victorian Information Privacy Act 2000, the Health Records Act 2001 or the Privacy Act 1988 (Commonwealth), as
Re: [Hibernate] useLimit problems.
Hmm posted too soon as always :-(
After studying the code some more I noticed that hibernate will use the
setMaxRows() method on the PreparedStatement instead of adding a limit
expression to the sql statement.
Hopefully this is just as good. I'll have to make sure it is.
Sorry for the inconvenience
Fredrik
From: "Fredrik Larsson" <[EMAIL PROTECTED]>
To: [EMAIL PROTECTED]
Subject: [Hibernate] useLimit problems.
Date: Tue, 05 Aug 2003 16:09:49 +0200
Hello.
I'm having some troubles with useLimit() in net.sf.hibernate.loader.Loader
(hibernate 2.0)
The method looks like this
private boolean useLimit(RowSelection selection, SessionImplementor
session) {
Dialect d = session.getFactory().getDialect();
return d.supportsLimit() &&
( selection!=null && selection.getMaxRows()!=null ) && //there
is a max rows
( d.preferLimit() || getFirstRow(selection)!=0 );
}
My problem is that I want use setFirstResult(0), setMaxResults(100) when I
retrieve the first part of a LAAARGE result set. Because of the
getFirstRow(selection)!=0 expression in the implementation above a limit
clause will not be added to the SQL statement.
My workaround is setFirstResult(1) but then I will not be able to retrieve
one row (the first one) from the database.
Question:
Am I missing something obvious here or is this a bug?
Kind Regards
Fredrik Larsson
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[Hibernate] Help Wanted :)
David Channon has implemented support for Dialect-specific SQL functions in the HQL select clause. This means that we need to go though the dialects, one by one, and fill in the standard functions for that Dialect. David has already done this for Oracle. It would be very nice if some platform experts could help by submitting patches for the others. Thanks! ** Any personal or sensitive information contained in this email and attachments must be handled in accordance with the Victorian Information Privacy Act 2000, the Health Records Act 2001 or the Privacy Act 1988 (Commonwealth), as applicable. This email, including all attachments, is confidential. If you are not the intended recipient, you must not disclose, distribute, copy or use the information contained in this email or attachments. Any confidentiality or privilege is not waived or lost because this email has been sent to you in error. If you have received it in error, please let us know by reply email, delete it from your system and destroy any copies. ** --- This SF.Net email sponsored by: Free pre-built ASP.NET sites including Data Reports, E-commerce, Portals, and Forums are available now. Download today and enter to win an XBOX or Visual Studio .NET. http://aspnet.click-url.com/go/psa0013ave/direct;at.aspnet_072303_01/01 ___ hibernate-devel mailing list [EMAIL PROTECTED] https://lists.sourceforge.net/lists/listinfo/hibernate-devel
[Hibernate] Help : Bidirectionally Polymorphic One to Many associations
I have the following scenario and have been unable to resolve the underlying issues by reading either the manual or the faq. I have two inheritance hierarchies. eg. Customer is a base class and InternalCustomer and ExternalCustomer are derived classes. Similarly Location is a base class whereas IndustrialLocation and CommercialLocation are derived classes. We have chosen to implement the table-per-concreteclass strategy (ie. each table has columns for the base class as well). So in a scenario where say an Invoice needs a reference to a customer, I have set up an "" relationship from invoice to customer, by using customerType and customerId columns in the invoice table. However we need to setup a "one-to-many" relationship between a customer and a location (ie. polymorphic both ways with tables created for leaf classes only). This can be easily done at a table level by creating "customerType" and "customerId" columns in each of the location tables. I have also been able to be able to reference the customer object from a location object by using the "" tag in the hbms of the location classes. I am unable to decide how to implement the relationship from customer to location using hibernate. I am looking for the ability to implement the "Set getLocations()" method in Customer. The following option does come to my mind (not certain if it is necessarily implementable) a. Implement getIndustrialLocations() and getCommercialLocations() seperately. This requires my customer class to not be able to deal with Locations polymorphically. Moreover it will require me to modify the source as and when I add new Derived classes for Location. I am however struggling for a better solution. Any suggestions will be welcome. Thanks Dhananjay --- This SF.Net email sponsored by: Free pre-built ASP.NET sites including Data Reports, E-commerce, Portals, and Forums are available now. Download today and enter to win an XBOX or Visual Studio .NET. http://aspnet.click-url.com/go/psa0013ave/direct;at.aspnet_072303_01/01 ___ hibernate-devel mailing list [EMAIL PROTECTED] https://lists.sourceforge.net/lists/listinfo/hibernate-devel
[Hibernate] outer-join attribute for collection mappings
Well, I still think that this is almost always a Bad Thing, but it is now possible to configure (exactly one) collection to be loaded by outer join in the mapping file. This will affect the fetching beviour for * load() * Criteria queries * lazy association access It does not affect the behaviour of HQL queries, which provide the FETCH clause. Implementing this feature did allow me to make some nice design improvements to OuterJoinLoader. Theres still some extra thought to go on the code which decides exactly when to do the outer join and when not to. This feature could result in some extremely deep fetching, so I'm thinking of adding a hibernate.max_outerjoin_fetch_depth property or something. All in v21branch. ** Any personal or sensitive information contained in this email and attachments must be handled in accordance with the Victorian Information Privacy Act 2000, the Health Records Act 2001 or the Privacy Act 1988 (Commonwealth), as applicable. This email, including all attachments, is confidential. If you are not the intended recipient, you must not disclose, distribute, copy or use the information contained in this email or attachments. Any confidentiality or privilege is not waived or lost because this email has been sent to you in error. If you have received it in error, please let us know by reply email, delete it from your system and destroy any copies. ** --- This SF.Net email sponsored by: Free pre-built ASP.NET sites including Data Reports, E-commerce, Portals, and Forums are available now. Download today and enter to win an XBOX or Visual Studio .NET. http://aspnet.click-url.com/go/psa0013ave/direct;at.aspnet_072303_01/01 ___ hibernate-devel mailing list [EMAIL PROTECTED] https://lists.sourceforge.net/lists/listinfo/hibernate-devel
RE: [Hibernate] Moving Hibernate objects with SOAP
Title: RE: [Hibernate] Moving Hibernate objects with SOAP Hi Jon, One of the things that I currently do is use XDoclet to generate inline transforms for going back and forth from XML to entity. You end up with hardcoded serializers, which are very fast, but I don't have enough experience with it yet to know what extended maintenance is going to be like. It would theoretically be possible to generate a schema/dtd that goes with the serializers, and one maintenance process might rename the then-current serializers and schema pair to something new as the system grew (giving the ability to support backwards compatibility). Some environments won't need all this though. Note that I am currently using it with XDoclet value objects (DTOs, if I understand the two correctly) from entity beans. So what I have will need a bit of work to make it work with Hibernate POJOs, but not much and I plan on doing that work within the next few days. As it works today, simply changing your XDoclet tags for your entities rewrites the serializers automagically. The same thing will happen with the POJOs when I am done. I can forward or post what I have when I have it for anyone that is interested. I've thought about integrating this into the mainline XDoclet tree, but wanted to get some experience with it first. If anyone has thoughts about such an integration (pro/con), please share. best, -b -Original Message-From: Jon Lipsky [mailto:[EMAIL PROTECTED]Sent: Thursday, August 07, 2003 4:59 PMTo: 'Josh Rehman'; '[EMAIL PROTECTED]'Subject: RE: [Hibernate] Moving Hibernate objects with SOAP Hi Josh, I needed to send my objects over SOAP as well (though using GLUE, not Axis). What I ended up doing was write a custom serializer/deserializer that would write my hibernate data objects to and from XML. When I want to send the object over the wire, it is serialzed to XML, and then on the client side it deserialzed back into it's object state. Doing it this way means that I have fine control over how much of the data hibernate lazily loads, meaning it only loads what I want it to send over the wire. The methods that are exposed with SOAP just send byte arrays around, and there is an API that wraps those methods that to handle the deserialization/serialization. Doing it this way allowed me to avoid having to add special "DTO" objects into my model. Regards, Jon... -Original Message- From: Josh Rehman [mailto:[EMAIL PROTECTED]] Sent: Thursday, August 07, 2003 2:46 AM To: [EMAIL PROTECTED] Subject: [Hibernate] Moving Hibernate objects with SOAP Hello all, I'd like to move Hibernate generated objects (generated with hbm2java, of course) across the wire with SOAP. There are two problems: First, Hibernate generates collection accessors. This is great, but these are, by necessity, untyped. The Axis serializer cannot handle this. Second, it often comes to pass that we are only interested in a subset of the object. In particular, we often do NOT want to move an entire collection accross the wire. Unfortunately, the serializer will call all accesors on the hibernate object, and CGLIB will, of course, do it's job and get everything known about that object. We have so far tried to solve these problems by writing an additional code generator that creates so-called "Data Transfer Objects" (Fowler's term, also abreviated DTO) that have a) typed array accessors, and b) the ability to specify a subset of interesting properties. We aren't quite done with this effort, but it's so far working out well. The DTOs are generated by delegating work to an underlying hibernate class. Has anyone faced and solved, these probelms? If so, I'd like to hear about it. In particular, I was hoping that there is something obvious that I may have missed. With kind regards, Josh Rehman --- This SF.Net email sponsored by: Free pre-built ASP.NET sites including Data Reports, E-commerce, Portals, and Forums are available now. Download today and enter to win an XBOX or Visual Studio .NET. http://aspnet.click-url.com/go/psa0013ave/direct;at.aspnet_072303_01/01 ___ hibernate-devel mailing list [EMAIL PROTECTED] https://lists.sourceforge.net/lists/listinfo/hibernate-devel
Re: [Hibernate] hbm2java patch for generating find methods
This is already fixed in CVS - old news ;) Sorry that i did not bite on your posting earlier, but with approx. 150 mails per day regarding hibernate one or two will slip ;( /max [EMAIL PROTECTED] wrote: The following is in the patch. This patch is based on a question I posted earlier today (http://sourceforge.net/forum/forum.php?thread_id=912698&forum_id=128638), but got no bites on. I did have to change the build to work with hibernate-2.0.2 as the build.xml was looking for ../../hibernate-2.0/lib. I fixed two problems here. 1)Only findAll was getting generated, no matter how many finder-method's were defined at the property level. To fix this, I simply changed the value of MT_FINDERMETHOD from "finder" to "finder-method". 2)The wrong SQL or HQL was getting generated for the findAll() method. Basically, it had "from className in class package.className" and hibernate was complaining by something like: "unexpected token: in [from Organization in class net.sf.jameleon.jdo.Organization]". I took out the text "in class package.ClassName" for the findAll method generation code. I hope this helps. --- This SF.Net email sponsored by: Free pre-built ASP.NET sites including Data Reports, E-commerce, Portals, and Forums are available now. Download today and enter to win an XBOX or Visual Studio .NET. http://aspnet.click-url.com/go/psa0013ave/direct;at.aspnet_072303_01/01 ___ hibernate-devel mailing list [EMAIL PROTECTED] https://lists.sourceforge.net/lists/listinfo/hibernate-devel
Re: [Hibernate] Unit Testing With ThreadLocal Sessions
They are not coupled with the web tier. They only require _something else_ to close the session at the appropriate time. In a web application, it happens to be a servlet filter. In test cases, it happens to be the tearDown() method. There is no dependency on the web tier when running the test cases. If you have other scenarios, you just need to find an appropriate place to close the session (maybe a controller of some sort). Joe - Original Message - From: "Matthew E.Porter" <[EMAIL PROTECTED]> To: "Joseph Fifield" <[EMAIL PROTECTED]> Cc: <[EMAIL PROTECTED]> Sent: Wednesday, August 06, 2003 9:59 AM Subject: Re: [Hibernate] Unit Testing With ThreadLocal Sessions > My only concern with this is that the business logic component is now > coupled with the web tier. For this project (which is basically a > framework), we want to be able to use the components internal and > external to the servlet container. However, I do appreciate the > feedback! It helps confirm my thinking regarding potential solutions. > > > Cheers, >matthew > > On Wednesday, August 6, 2003, at 07:29 AM, Joseph Fifield wrote: > > > I don't close the session at all in any of my business logic methods. > > In > > deployment, a servlet filter _always_ closes the session at the end of > > the > > request. For unit testing, I have a base test case class that does the > > same > > thing in the tearDown() method. That way, each test case can execute > > in the > > same manner as the app running in deployment (i.e. each test case is > > like a > > separate "request"). The result is each test case executes using the > > same > > session, and they don't need to worry about closing it at the end. > > > > Hope this helps... > > > > Joe > > > > - Original Message - > > From: "Matthew E.Porter" <[EMAIL PROTECTED]> > > To: <[EMAIL PROTECTED]> > > Sent: Tuesday, August 05, 2003 11:12 PM > > Subject: [Hibernate] Unit Testing With ThreadLocal Sessions > > > > > >> Greetings. I am interested in hearing how people unit test method > >> that > >> call session.save(), update(), and delete() when the session is > >> provided via the ThreadLocal pattern. For me, the primary question is > >> whether or not the method containing the session method calls actually > >> closes the database connection (session.close()) or is it called after > >> returning from the tested method. From a pure unit testing > >> stand-point, it would seem that it would be desired to be called > >> inside > >> the tested method. > >> > >> For a project I am working on, we devised a solution (aka hack) to > >> solve this. A new Session interface implementation was created that > >> wraps an internal Session object as normally provided. Yet, we added > >> 2 > >> methods: suspendClose() and unsuspendClose(). When closes are > >> suspend, > >> the connection is NOT closed despite being called. Specifically, it > >> does not call session.close() on the internal Session object. > >> > >> When a Session is retrieved, the closes are automatically suspended. > >> The servlet filter unsuspends the close and closes the session if > >> necessary at the end of the request. > >> > >> Is this a hack? Yes. Does it work? Yes. Do we get the benefits of > >> a > >> ThreadLocal session? Yes. Can it be confusing to newbies who expect > >> close to actual close the session? Yes, but it only has this behavior > >> during deployment. > >> > >> Any thoughts and comments are welcome. > >> > >> > >> Cheers, > >>matthew > >> > >> > >> > >> --- > >> This SF.Net email sponsored by: Free pre-built ASP.NET sites including > >> Data Reports, E-commerce, Portals, and Forums are available now. > >> Download today and enter to win an XBOX or Visual Studio .NET. > >> > > http://aspnet.click-url.com/go/psa0013ave/ > > direct;at.aspnet_072303_01/01 > >> ___ > >> hibernate-devel mailing list > >> [EMAIL PROTECTED] > >> https://lists.sourceforge.net/lists/listinfo/hibernate-devel > >> > >> > > > > > > > > > > --- > > This SF.Net email sponsored by: Free pre-built ASP.NET sites including > > Data Reports, E-commerce, Portals, and Forums are available now. > > Download today and enter to win an XBOX or Visual Studio .NET. > > http://aspnet.click-url.com/go/psa0013ave/ > > direct;at.aspnet_072303_01/01 > > ___ > > hibernate-devel mailing list > > [EMAIL PROTECTED] > > https://lists.sourceforge.net/lists/listinfo/hibernate-devel > > > --- This SF.Net email sponsored by: Free pre-built ASP.NET sites including Data Reports, E-commerce, Portals, and Forums are available now. Download today and enter to win an XBOX or Visual Studio .NET. http://aspnet.click-url.com/go/psa0013ave/direct;at.aspnet_072303_01/01 _
[Hibernate] Problem with SchemaUpdate
Hi, ich have a class and a mapping. Now I enhance the class and mapping and I want to run SchemaUpdate from inside my code. I add a property 'old' to my code as well as to the mapping file. The generated sql update statement is: alter table xattr add columnold VARCHAR(20) alter table attributes add index (xxx), add constraint FK182DA9571D178 foreign key (xxx) references xattr (oid) I believe it should be 'alter table xattr add column old VARCHAR(20)' so a space between 'column' and 'old'. It added now a column called columnold and not old. I'm using 2.0.1 and mysql. Oliver --- This SF.Net email sponsored by: Free pre-built ASP.NET sites including Data Reports, E-commerce, Portals, and Forums are available now. Download today and enter to win an XBOX or Visual Studio .NET. http://aspnet.click-url.com/go/psa0013ave/direct;at.aspnet_072303_01/01 ___ hibernate-devel mailing list [EMAIL PROTECTED] https://lists.sourceforge.net/lists/listinfo/hibernate-devel
