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• How to customize pickle for django model objects

  - by muudscope

  I need to pickle a complex object that refers to django model objects. The standard pickling process stores a denormalized object in the pickle. So if the object changes on the database between pickling and unpickling, the model is now out of date. (I know this is true with in-memory objects too, but the pickling is a convenient time to address it.) So what I'd like is a way to not pickle the full django model object. Instead just store its class and id, and re-fetch the contents from the database on load. Can I specify a custom pickle method for this class? I'm happy to write a wrapper class around the django model to handle the lazy fetching from db, if there's a way to do the pickling.

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• Nhibernate Criteria Ignore Child Collection

  - by CocoB

  I have a simple one to many association in my model. The parent class has a collection of children. In the mapping files, the association is a one to many, eager-loaded, using fetchmode.join. This works fine, but how can I write a criteria query but NOT trigger the loading of the child collection? In other words, I want to query the parent and not have it generate the join in the resulting sql. I tried setting the fetch mode to lazy, but in that case Nhibernate generates two separate queries. I don't want the table for child queried at all.

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• Compile error when calling ToList() when accessing many to many with Linq To Entities

  - by KallDrexx

  I can't figure out what I am doing wrong. I have the following method: public IList<WObject> GetRelationshipMembers(int relId) { var members = from r in _container.ObjectRelationships where r.Id == relId select r.WObjects; return members.ToList<WObject>(); } This returns the following error: Instance argument: cannot convert from 'System.Linq.IQueryable<System.Data.Objects.DataClasses.EntityCollection<Project.DomainModel.Entities.WObject>>' to 'System.Collections.Generic.IEnumerable<Project.DomainModel.Entities.WObject>' How can I convert the EntityCollection to a list without lazy loading?

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• classes and static variables in shared libraries

  - by abel

  I am trying to write something in c++ with an architecture like: App -- Core (.so) <-- Plugins (.so's) for linux, mac and windows. The Core is implicitly linked to App and Plugins are explicitly linked with dlopen/LoadLibrary to App. The problem I have: static variables in Core are duplicated at run-time -- Plugins and App have different copys of them. at least on mac, when a Plugin returns a pointer to App, dynamic casting that pointer in App always result in NULL. Can anyone give me some explanations and instructions for different platforms please? I know this may seem lazy to ask them all here but I really cannot find a systematic answer to this question.

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• Microsoft T-SQL to Oracle PL/SQL translation

  - by Michael Prewecki

  I've worked with T-SQL for years but i've just moved to an organisation that is going to require writing some Oracle stuff, probably just simple CRUD operations at least until I find my feet. I'm not going to be migrating databases from one to the other simply interacting with existing Oracle databases from an Application Development perspective. Is there are tool or utility available to easily translate T-SQL into PL/SQL, a keyword mapper is the sort of thing I'm looking for. P.S. I'm too lazy to RTFM, besides it's not going to be a big part of my role so I just want something to get me up to speed a little faster.

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• struts 2 bean is not created

  - by Dewfy

  Hello colleagues! At first some precondition to my question, I'm using struts2 + tiles2 + toplink. NO spring at all. The simplest scenario - is to display list of entities on the page. To optimize resolving JPA's EntityManager I would like to create helper (JPAResourceBean) that implements lazy load of entity manager. For this purposes I'm going to use struts2's bean declaration: <bean name="myfactory" class="my.model.JPAResourceBean" scope="session" optional="false"/> Why bean is not instantiated neither in session? (I'm using s:property just for debug) ... <s:property value="#session.myfactory" default="buka.1"/> ... nor in plain bean list: ... <s:property value="#myfactory" default="buka.2"/> ... May be the second part of question is - how to resolve this bean from java code?

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• ManyToMany Relation does not create the primary key

  - by Javi

  Hello, I have a ManyToMany relationship between two classes: ClassA and ClassB, but when the table for this relationship (table called objectA_objectB) there is no primary key on it. In my ClassA I have the following: @ManyToMany(fetch=FetchType.LAZY) @OrderBy(value="name") @JoinTable(name="objectA_objectB", joinColumns= @JoinColumn(name="idObjectA", referencedColumnName="id"), inverseJoinColumns= @JoinColumn(name="idObjectB", referencedColumnName="id") ) private List<ClassB> objectsB; and in my ClassB I have the reversed relation @ManyToMany List<ClassA> objectsA; I just want to make a primary key of both id's but I need to change the name of the columns as I do. Why is the PK missing? How can I define it? I use JPA 2.0 Hibernate implementation, if this helps. Thanks.

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• phpDocumentor alternative consuming less memory

  - by Michal Cihar

  Okay, I'm fed up with phpDocumentator. It consumes way much more memory and time than I'm willing to give it. Does there exist some really compatible program to generate documentation for PHP code? I've tried PHPDoctor, which looks nice, but it has some missing features. I've also tried PhpDocGen, but it just bails out with some Perl errors, which I'm too lazy to study. Doxygen also does not seem to play well with our sources. PS: The documentation would be for phpMyAdmin, a little bit outdated documentation is here.

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• Check For Duplicate Records VS try/catch Unique Key Constraint

  - by Jed

  I have a database table that has a Unique Key constraint defined to avoid duplicate records from occurring. I'm curious if it is bad practice to NOT manually check for duplicate records prior to running an INSERT statement on the table. In other words, should I run a SELECT statement using a WHERE clause that checks for duplicate values of the record that I am about to INSERT. If a record is found, then do not run the INSERT statement, otherwise go ahead and run the INSERT.... OR Just run the INSERT statement and try/catch the exception that may be thrown due to a Unique Key violation. I'm weighing the two perspectives and can't decide which is best- 1. Don't waste a SELECT call to check for duplicates when I can just trap for an exception VS 2. Don't be lazy by implementing ugly try/catch logic VS 3. ???Your thoughts here??? :)

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• Should I replace string patterns in asp.net mvc using a custom viewengine?

  - by Roger Rogers

  Have an ASP.NET MVC site that is localized. The localization functionality adds the two digit language ID to the URL, e.g. /es/Page. If no language Id is found in the URL, the site switches to the user's browser culture. All's good. However, the site's hyperlinks, a mixture of hard-coded href tags, actionlinks, etc., don't include the base language ID, so when clicking through the site the set culture is lost, and the site reverts to the user's browser culture. My (lazy) thought is to replace all href values, that don't point to an external site, with the localized URL (e.g. include the /es/). Otherwise, all site links will need to be updated to include the culture code. Is this just plain dumb? Or, reasonable, and should be done using a custom view engine, or some other approach?

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• Query not returning rows in a table that don't have corresponding values in another [associative] ta

  - by Obay

  I have Table: ARTICLES ID | CONTENT --------------- 1 | the quick 2 | brown fox 3 | jumps over 4 | the lazy Table: WRITERS ID | NAME ---------- 1 | paul 2 | mike 3 | andy Table: ARTICLES_TO_WRITERS ARTICLE_ID | WRITER_ID ----------------------- 1 | 1 2 | 2 3 | 3 To summarize, article 4 has no writer. So when I do a "search" for articles with the word "the": SELECT a.id, a.content, w.name FROM articles a, writers w, articles_to_writers atw WHERE a.id=atw.article_id AND w.id=atw.writer_id AND content LIKE '%the%' article 4 does not show up in the result: ID | CONTENT | NAME ----------------------- 1 | the quick | paul How do I make article 4 still appear in the results even though it has no writers?

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• Does performance even matter anymore? [closed]

  - by Jeff Dahmer

  The performance differences between C/C++ and C# are astounding. An ASP.NET page loads in 1/8 the time that a PHP script does haha.... WPF, aka " The Future ", (you know it will be, all the companies are gonna want cool looking desktop apps, don't kid yourself.) And it has huge performance hits just to start up. We've let Microsoft make us as developers lazy! Why do I hate this, it's such a good thing? Are we at a point in time where the majority of computers can handle this kinda crap? I remember when performance used to matter. Anyways, I'm writing a .NET library and ever since I found out LINQ is slower than traditional delegates which is slower than the normal procedural code... well it's a guilty evil I feel for every LINQ query I write, because they are so beautiful. Am I just too much of a performance stickler? Or just too big of a nerd?

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• Why does an event handler never get called if it's added within a loop on an ienumerable?

  - by André Carvalho

  Why does an event handler never get called if it's added within a loop on an ienumerable? For instance: IEnumerable<MyType> list = someCollection.Select(i => new MyType(i)); foreach (var item in list) item.PropertyChanged += item_PropertyChanged; <-- this never gets called Bu if list is assigned like list = someCollection.Select(i => new MyType(i)).ToArray(); the event handler does get called.. Why? (I imagine it has something to do with the fact that a LINQ query is lazy, but the fact of looping through the result isn't enough?)

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• GAE datastore eager loading in python api

  - by tomus

  I have two models in relation one-to-many: class Question(db.Model): questionText = db.StringProperty(multiline=False) class Answer(db.Model): answerText = db.StringProperty(multiline=False) question = db.ReferenceProperty(Question, collection_name='answers') I have front-end implemented in Flex and use pyamf to load data. When i try to load all answers with related questions all works as desired and I can access field answer.question however in case of loading questions (e.g. by Questions.all() ), 'question.answers' remains empty/null (though on server/python side I can revise question.answers without problem - probably after lazy-loading). So is it possible to load all questions along with answers ? (I know this is possible in JPA Java api but what about python ?) Shoud I use additional setting, GQL query or django framework to make it work ?

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• Confusion regarding laziness

  - by Abhinav Kaushik

  I have a function myLength = foldl (\ x _ -> x + 1) 0 which fails with stack overflow with input around 10^6 elements (myLength [1..1000000] fails). I believe that is due to the thunk build up since when I replace foldl with foldl', it works. So far so good. But now I have another function to reverse a list : myReverse = foldl (\ acc x -> x : acc) [] which uses the lazy version foldl (instead of foldl') When I do myLength . myReverse $ [1.1000000]. This time it works fine. I fail to understand why foldl works for the later case and not for former?

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• By-Name-Parameters for Constructors

  - by hotzen

  Hello, coming from my other question is there a way to get by-name-parameters for constructors working? I need a way to provide a code-block which is executed on-demand/lazy/by-name inside an object and this code-block must be able to access the class-methods as if the code-block were part of the class. Following Testcase fails: package test class ByNameCons(code: => Unit) { def exec() = { println("pre-code") code println("post-code") } def meth() = println("method") def exec2(code2: => Unit) = { println("pre-code") code2 println("post-code") } } object ByNameCons { def main(args: Array[String]): Unit = { val tst = new ByNameCons { println("foo") meth() // knows meth() as code is part of ByNameCons } tst.exec() // ByName fails (executed right as constructor) println("--------") tst.exec2 { // ByName works println("foo") //meth() // does not know meth() as code is NOT part of ByNameCons } } } Output: foo method pre-code post-code -------- pre-code foo post-code

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• WPF ListView.CurrentChanged too fast for binding

  - by matt

  My case: MVVM ListView+Details(custom UserControl) List bound to MV.Items (IsSynchronizedWithCurrent=true) Details bound to MV.Items.Current MV.Items.Count == 100 about 0.2sec to read details (lazy mode) When I hold the down arrow on the list, very strange things happen: list items order change current changes in the random order CPU usage drastically increments and eventually all hangs. I've read some post that one should start the timer or run handler in the background, but I am not able to do that, since all the binding WPF does for me. Is there some way to instruct the binding in my DetailsControl, to wait a while before accepting CurrentItem? Or should I just resign from the clean solution and write custom code in my MV to handle that?

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• Too many values problem

  - by DraskyVanderhoff

  Hi , i was trying to make a full lot of ips for testing using this code : ip_is = [i for i in range(256)] ports = [i for i in range(1024,49152)] return [str(i1)+"."+str(i2)+"."+str(i3)+"."+str(i4)+":"+str(p) for i1,i2,i3,i4,port in ip_is,ip_is,ip_is,ip_is,ports] The problem is the 3rd line in which is made the ip list. If there is a way to make it all at once or how can make one at time in a lazy way ? I'm pretty noob at python :P. Thanks for the Help :)

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• list-index hibernate ?

  - by kumar kasimala

  Hi I am bit confusion of list index type,my mapping file has like below <list name="transactionItems" cascade="save-update,delete-orphan" lazy="false"> <key column="TRANSACTION_ID" /> <list-index column="IDX" /> <one-to-many class="TransactionItem" /> </list> whenever hibernate load a mapped object,its through exception null index column for collection:transactionItems please suggest me what can be the problem here. can you exaplain a bit about list-index? thanks & Regards kumar kasiamla India,Hyderabad.

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• Can I partition the C# System.Threading.ThreadPool?

  - by Drew Shafer

  I love ThreadPool. It makes my life better. However, my love may have quietly turned into an abusive relationship that I need to escape from, so I need some advice from my SO brothers (and presumably sisters, although I haven't seen any actual evidence of that yet). My basic problem is that I have several different libraries that are all using the threadpool in an uncoordinated way, and running out of threads is a possibility. I was hoping there was some way I could partition the ThreadPool up so I could give a certain class 1 thread, another 20 threads, another 5 threads, and so on. I know I could write my own ThreadPool implementation. I don't want to do that, because I'm lazy. So, is there a simple solution already out there? Currently I'm constrained to using the 3.5 CLR. I know a lot of this stuff becomes easier in 4.0.

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• JPA entitymanager remove operation is not performant

  - by Samuel

  When I try to do an entityManager.remove(instance) the underlying JPA provider issues a separate delete operation on each of the GroupUser entity. I feel this is not right from a performance perspective, since if a Group has 1000 users there will be 1001 calls issued to delete the entire group and itr groupuser entity. Would it make more sense to write a named query to remove all entries in groupuser table (e.g. delete from group_user where group_id=?), so I would have to make just 2 calls to delete the group. @Entity @Table(name = "tbl_group") public class Group { @OneToMany(mappedBy = "group", cascade = CascadeType.ALL, fetch = FetchType.LAZY) @Cascade(value = DELETE_ORPHAN) private Set<GroupUser> groupUsers = new HashSet<GroupUser>(0);

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• JPA : Inheritance - Discriminator value not taken into account in generated SQL

  - by Julien

  I try to use this mapping : @Entity @Table(name="ecc.\"RATE\"") @Inheritance(strategy=InheritanceType.SINGLE_TABLE) @DiscriminatorColumn(name="DISCRIMINATOR", discriminatorType= DiscriminatorType.STRING) public abstract class Rate extends GenericBusinessObject { ... } @Entity @DiscriminatorValue("E") public class EntranceRate extends Rate { @ManyToOne @JoinColumn(name = "\"RATES_GRID_ID\"") protected RatesGrid ratesGrid; ... } @Entity @Table(name="ecc.\"RATES_GRID\"") public class RatesGrid extends GenericBusinessObject { /** */ @OneToMany(mappedBy = "ratesGrid", targetEntity = EntranceRate.class, fetch=FetchType.LAZY) private List<EntranceRate> entranceRates; } When I try to access my entranceRates list from a ratesGrid object, I get this error : Object with id: 151 was not of the specified subclass: com.ecc.bo.rate.EntranceRate (loaded object was of wrong class class com.ecc.bo.rate.AnnualRate) Looking at the sql generated, I found no trace of "discriminator=" in the where clause. What am I doing wrong ? I use a PostGreSQL database and a Hibernate as JPA provider.

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• How do I write a constant-space length function in Haskell?

  - by Bill

  The canonical implementation of length :: [a] -> Int is: length [] = 0 length (x:xs) = 1 + length xs which is very beautiful but suffers from stack overflow as it uses linear space. The tail-recursive version: length xs = length' xs 0 where length' [] n = n length' (x:xs) n = length xs (n + 1) doesn't suffer from this problem, but I don't understand how this can run in constant space in a lazy language. Isn't the runtime accumulating numerous (n + 1) thunks as it moves through the list? Shouldn't this function Haskell to consume O(n) space and lead to stack overflow? (if it matters, I'm using GHC)

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• VS2012 equivalent of Eclipse's default Ctrl-Shift-O?

  - by x3chaos

  I'm used to Java (in Eclipse), which has its import statements, but I'm writing a DLL in Visual C# (in Visual Studio 2012), which has its using statements. I'm used to Eclipse's default keyboard shortcut Ctrl-Shift-O, which updates the list of import statements in the Java perspective, deleting unused imports and adding necessary imports found on the build path. Is there an equivalent operation in VS2012 with VC#? I've just been selecting the word, opening the Office-style popup, and added the "using" statement that way, but it conflicts with my workflow (read: I'm lazy and I like having my shortcuts).

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• Nibernate, DynamicProxy, and Spring AOP

  - by jeff

  We have an Spring IOC managed application that uses NHibernate in its persistence layer. We have use the Spring AOP and understand its terminology and capabilities. We have some investment in Spring proxies. Now, we want to add a PropertyChangedMixin and a ValidatorInterceptor (not nhibernate validator, but based on Spring validation) onto our NHibernate managed objects. I've looked at the hooks for NHiberate IInterceptor and EventListeners and that gives me a place to apply the desired proxies. If I use the Spring proxies is it going to play nice with the existing nhibernate proxies. We don't lazy load. From the simple nhibernate stuff the benefits of DynamicProxy look appealing. I can go either way, but I'd like to hear suggestions. Thanks, jeff

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