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  • FluentNHibernate: multiple one-to-many relationships between the same entities.

    - by Venemo
    Hi, I'm working on a bug tracking application. There are tickets, and each ticket has an opener user and an assigned user. So, basically, I have two entities, which have two many-to-one relationships with each other. Their schematic is this: User: public class User { public virtual int Id { get; private set; } ... public virtual IList<Ticket> OpenedTickets { get; set; } public virtual IList<Ticket> AssignedTickets { get; set; } } Ticket: public class Ticket { public virtual int Id { get; protected set; } ... [Required] public virtual User OpenerUser { get; set; } public virtual User AssignedUser { get; set; } } I use FluentNHibernate's auto mapping feature. The problem is, that no matter whether relationship I set, on the side of the User, both collections always contain the same data. I guess Fluent can't tell which end of which relationship belongs to where. I googled around but haven't found anything useful. Could anyone help me, please?

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  • Overly accessible and incredibly resource hungry relationships between business objects. How can I f

    - by Mike
    Hi, Firstly, This might seem like a long question. I don't think it is... The code is just an overview of what im currently doing. It doesn't feel right, so I am looking for constructive criticism and warnings for pitfalls and suggestions of what I can do. I have a database with business objects. I need to access properties of parent objects. I need to maintain some sort of state through business objects. If you look at the classes, I don't think that the access modifiers are right. I don't think its structured very well. Most of the relationships are modelled with public properties. SubAccount.Account.User.ID <-- all of those are public.. Is there a better way to model a relationship between classes than this so its not so "public"? The other part of this question is about resources: If I was to make a User.GetUserList() function that returns a List, and I had 9000 users, when I call the GetUsers method, it will make 9000 User objects and inside that it will make 9000 new AccountCollection objects. What can I do to make this project not so resource hungry? Please find the code below and rip it to shreds. public class User { public string ID {get;set;} public string FirstName {get; set;} public string LastName {get; set;} public string PhoneNo {get; set;} public AccountCollection accounts {get; set;} public User { accounts = new AccountCollection(this); } public static List<Users> GetUsers() { return Data.GetUsers(); } } public AccountCollection : IEnumerable<Account> { private User user; public AccountCollection(User user) { this.user = user; } public IEnumerable<Account> GetEnumerator() { return Data.GetAccounts(user); } } public class Account { public User User {get; set;} //This is public so that the subaccount can access its Account's User's ID public int ID; public string Name; public Account(User user) { this.user = user; } } public SubAccountCollection : IEnumerable<SubAccount> { public Account account {get; set;} public SubAccountCollection(Account account) { this.account = account; } public IEnumerable<SubAccount> GetEnumerator() { return Data.GetSubAccounts(account); } } public class SubAccount { public Account account {get; set;} //this is public so that my Data class can access the account, to get the account's user's ID. public SubAccount(Account account) { this.account = account; } public Report GenerateReport() { Data.GetReport(this); } } public static class Data { public static List<Account> GetSubAccounts(Account account) { using (var dc = new databaseDataContext()) { List<SubAccount> query = (from a in dc.Accounts where a.UserID == account.User.ID //this is getting the account's user's ID select new SubAccount(account) { ID = a.ID, Name = a.Name, }).ToList(); } } public static List<Account> GetAccounts(User user) { using (var dc = new databaseDataContext()) { List<Account> query = (from a in dc.Accounts where a.UserID == User.ID //this is getting the user's ID select new Account(user) { ID = a.ID, Name = a.Name, }).ToList(); } } public static Report GetReport(SubAccount subAccount) { Report report = new Report(); //database access code here //need to get the user id of the subaccount's account for data querying. //i've got the subaccount, but how should i get the user id. //i would imagine something like this: int accountID = subAccount.Account.User.ID; //but this would require the subaccount's Account property to be public. //i do not want this to be accessible from my other project (UI). //reading up on internal seems to do the trick, but within my code it still feels //public. I could restrict the property to read, and only private set. return report; } public static List<User> GetUsers() { using (var dc = new databaseDataContext()) { var query = (from u in dc.Users select new User { ID = u.ID, FirstName = u.FirstName, LastName = u.LastName, PhoneNo = u.PhoneNo }).ToList(); return query; } } }

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  • What is the best resizable circular byte buffer available in Java?

    - by Wouter Lievens
    I need a byte buffer class in Java for single-threaded use. I should be able to insert data at the back of the buffer and read data at the front, with an amortized cost of O(1). The buffer should resize when it's full, rather than throw an exception or something. I could write one myself, but I'd be very surprised if this didn't exist yet in a standard Java package, and if it doesn't, I'd expect it to exist in some well-tested public library. What would you recommend?

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  • How do I create many-one relationships using Scaffold?

    - by Simon
    I'm new to Ruby on Rails, and I'm trying to create a bass guitar tutor in order to teach myself RoR (and bass guitar). The walkthroughs use Scaffold to create ActiveRecord classes, but they seem to correspond to standalone tables; there's no use of belongs_to or has_many. I'd like to create three classes: Scale, GuitarString, and Fret. Each Scale has many GuitarStrings, which each have many Frets. How do I create classes with this relationship using Scaffold? Is there a way to do it in one go, or do I need to create them in an unrelated state using Scaffold, then add the relations by hand? Or should I ditch Scaffold entirely?

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  • How to add a column via a query which counts the total rows with a specific criteria in a table with circular relationship in MS ACCESS 2007

    - by Xaqron
    I have a simple table "Employees" with this fields: ID, ParentID, Name ParentID is Nullable since an employee may have no Manager. This table has a one-to-many relationship with itself: ID --one--to--many--> ParentID Now I want a query which returns this columns: Name, Count of rows where their ParentID equals to the current row ID (the row is the manager of that rows) Sample Table: ID | ParentID | Name ====================== 1 | 0 | John ---------------------- 2 | 1 | Bob ---------------------- 3 | 1 | Alice ---------------------- 4 | 3 | Jack This way I can find an employee is the manager of how many other employees. The result should be something like this: Name | Count of Employees ========================== John | 2 -------------- Bob | 0 -------------- Alice | 1 -------------- Jack | 0 How can I achieve this in MS ACCESS 2007? * I have tried built-in query builder without any success.

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  • How should I manage my many-to-many relationships?

    - by wes
    Hello all, I have a database containing a couple tables: files and users. This relationship is many-to-many, so I also have a table called users_files_ref which holds foreign keys to both of the above tables. Here's the schema of each table: files - file_id, file_name users - user_id, user_name users_files_ref - user_file_ref_id, user_id, file_id I'm using Codeigniter to build a file host application, and I'm right in the middle of adding the functionality that enables users to upload files. This is where I'm running into my problem. Once I add a file to the files table, I will need that new file's id to update the users_files_ref table. Right now I'm adding the record to the files table, and then I imagined I'd run a query to grab the last file added, so that I can get the ID, and then use that ID to insert the new users_files_ref record. I know this will work on a small scale, but I imagine there is a better way of managing these records, especially in a heavy-traffic scenario. I am new to relational database stuff but have been around PHP for a while, so please bear with me here :-) I have primary and foreign keys set up correctly for the files, users, and users_files_ref tables, I'm just wondering how to manage the adding of file records for this scenario? Thanks for any help provided, it's much appreciated. -Wes

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  • How do I create self-relationships in polymorphic inheritance in Elixir and Pylons?

    - by Turukawa
    I am new to programming and am following the example in the Pylons documentation on creating a Wiki. The database I want to link to the wiki was created with Elixir so I rewrote the Wiki database schema and have continued from there. In the wiki there is a requirement for a Navigation table which is inherited by Pages and Sections. A section can have many pages, while a page can only have one section. In addition, each sibling node can be chain-referenced to each other. So: Nav has "section" (OneToMany) and "before" (OneToOne - to reference preceeding node) Page has "section" (ManyToOne - many pages in one section) and inherits "before" Section inherits all from Nav The code I've written looks like this: class Nav(Entity): using_options(inheritance='multi') name = Field(Unicode(30), default=u'Untitled Node') path = Field(Unicode(255), default=u'') section = OneToMany('Page', inverse='section') after = OneToOne('Nav', inverse='before') before = OneToMany('Nav', inverse='after') class Page(Nav): using_options(inheritance='multi') content = Field(UnicodeText, nullable=False) posted = Field(DateTime, default=now()) title = Field(Unicode(255), default=u'Untitled Page') heading = Field(Unicode(255)) tags = ManyToMany('Tag') comments = OneToMany('Comment') section = ManyToOne('Nav', inverse='section') class Section(Nav): using_options(inheritance='multi') Errors received on this: sqlalchemy.exc.OperationalError: (OperationalError) table nav has no column named aftr_id u'INSERT INTO nav (name, path, aftr_id, row_type) VALUES (?, ?, ?, ?)' I've also tried: before = ManyToMany('Nav', inverse='before') on Nav in the hopes this might break the problem, but also not. The original SQLAlchemy code from the tutorial for these declarations is as follows: nav_table = schema.Table('nav', meta.metadata, schema.Column('id', types.Integer(), schema.Sequence('nav_id_seq', optional=True), primary_key=True), schema.Column('name', types.Unicode(255), default=u'Untitled Node'), schema.Column('path', types.Unicode(255), default=u''), schema.Column('section', types.Integer(), schema.ForeignKey('nav.id')), schema.Column('before', types.Integer(), default=None), schema.Column('type', types.String(30), nullable=False) ) page_table = schema.Table('page', meta.metadata, schema.Column('id', types.Integer, schema.ForeignKey('nav.id'), primary_key=True), schema.Column('content', types.Text(), nullable=False), schema.Column('posted', types.DateTime(), default=now), schema.Column('title', types.Unicode(255), default=u'Untitled Page'), schema.Column('heading', types.Unicode(255)), ) section_table = sa.Table('section', meta.metadata, schema.Column('id', types.Integer, schema.ForeignKey('nav.id'), primary_key=True), ) orm.mapper(Nav, nav_table, polymorphic_on=nav_table.c.type, polymorphic_identity='nav') orm.mapper(Section, section_table, inherits=Nav, polymorphic_identity='section') orm.mapper(Page, page_table, inherits=Nav, polymorphic_identity='page', properties={ 'comments':orm.relation(Comment, backref='page', cascade='all'), 'tags':orm.relation(Tag, secondary=pagetag_table) }) Any help is much appreciated.

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  • How to deal with many to many relationships with NSFetchedResultsController?

    - by Phil Yates
    OK so I have two entities in my data model (let's say entityA and entityB), both of these entities have a to-many relationship to each other. I have setup a NSFetchedResultsController to fetch a bunch of entityA. Now I'm trying to have the section names for the tableview be the title of entityB. sectionNameKeyPath:@"entityB.title" Now this causes a problem, where by the section name returned from that relationship appears to be ({title1}) or ({title1,title2...titleN}) obviously depending on how many different entityB's are involved. This doesn't look great in a tableview and doesn't group the objects as I would like. What I would like is a section per entityB title with entityA appearing under each section, under multiple sections if necessary. I'm at a loss as how I am supposed to achieve this whether I need to update the predicate to get the entity to appear multiple times or whether I need to update the section and header functions to do some processing as the controller loops through the objects. Any help is appreciated :) Thanks

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  • how to add a entry to tables with relationships?

    - by siulamvictor
    I have 2 models, Users & Accounts. They are in one-to-many relationship, i.e. each accounts have many users. Accounts company_id company_name company_website Users user_id user_name password company_id email How can I add these entries to database using ActiveRecord? Supposed I don't is the company existed in the database when I add a new entry. Name Email Password Company ----------------------------------------------------------------------------- Albert [email protected] 123456 ABC Company Betty [email protected] 234567 ABC Company Carmen [email protected] 765432 XXX Company David [email protected] 654321 ABC Company

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  • Minify an Entire Directory While Keeping Element/Style/Script Relationships?

    - by Jonathan Sampson
    Do any solutions currnetly exist that can minify an entire project directory? More importantly, do any solutions exist that can shorten classnames, id's, and keep them consistent throughout all documents? Something that can turn this: Index.html --- <div class="fooBar"> <!-- Code --> </div> Styles.css --- .fooBar { // Comments and Messages background-color:#000000; } Index.js --- $(".fooBar").click(function(){ /* More Comments */ alert("fooBar"); }); Into This: Index.html --- <div class="a"></div> Styles.css --- .a{background-color:#000;} Index.js --- $(".a").click(function(){alert("fooBar");});

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  • Mapping one to one foreign key relationships in Entity Framework 4.0?

    - by John K.
    Hello all, I'm sure I'm missing something very simple, but let's say I have two entities, Employee and EmployeeType. Employee type would contain values like 'Full time', 'Contractor', 'Intern', etc. An Employee entity would contain one, and only one EmployeeType value. So I am designing a new .edmx model using the Model-First approach and generating my actual sql server data schema from the model. I want to add an integer type foreign key id into my Employee entity, EmployeeTypeId, which will map to the primary key of the EmployeeType entity. So I've gone ahead and done that in my Employee entity. Where I'm stuck is how, though the Entity Framework designer, to enforce the 1:1 referential constraint on that EmployeeTypeId property? Or does the EF handle that automatically behind the scenes? thanks in advance, John

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  • KODO: how set up fetch plan for bidirectional relationships?

    - by BestPractices
    Running KODO 4.2 and having an issue inefficient queries being generated by KODO. This happens when fetching an object that contains a collection where that collection has a bidrectional relationship back to the first object. Class Classroom { List<Student> _students; } Class Student { Classroom _classroom; } If we create a fetch plan to get a list of Classrooms and their corresponding Students by setting up the following fetch plan: fetchPlan.addField(Classroom.class,”_students”); This will result in two queries (get the classrooms and then get all students that are in those classrooms), which is what we would expect. However, if we include the reference back to the classroom in our fetch plan in order for the _classroom field to get populated by doing fetchPlan.addField(Student.class, “_classroom”), this will result in X number of additional queries where X is the number of students in each classroom. Can anyone explain how to fix this? KODO already has the original Classroom objects at the point that it's executing the queries to retrieve the Classroom objects and set them in each Student object's _classroom field. So I would expect KODO to simply set those objects in the _classroom field on each Student object accordingly and not go back to the database. Once again, the documentation is sorely lacking with Kodo/JDO/OpenJPA but from what I've read it should be able to do this more efficiently. Note-- EAGER_FETCH.PARALLEL is turned on and I have tried this with caching (query and data caches) turned on and off and there is no difference in the resultant queries.

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  • Is it possible to write a database view that encompasses one-to-many relationships?

    - by Brandon Linton
    So I'm not necessarily saying this is even a good idea if it were possible, since the schema of the view would be extremely volatile, but is there any way to represent a has-many relationship in a single view? For example, let's say I have a customer that can have any number of addresses in the database. Is there any way to list out each column of each address with perhaps a number as a part of the alias (e.g., columns like Customer Id, Name, Address_Street_1, Address_Street_2, etc)? Thanks!

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  • Foreign Key vs. Independent Relationships - is there improvement with Entity Framework 5?

    - by zam6ak
    I have read several articles and questions on concept of foreign key vs independent relationship when using Entity Framework. And I am still not 100% sure which way to go.... I would prefer not to "pollute" my domain POCOs by having a property that will be used in FK relationship when I already have a property reference to "has a" object. My questions are (looking at you @EFTeam, @Ladislav Mrnka) are there any improvements on this subject in the upcoming Entity Framework v5? are there more advantages if I use FK instead of independent associations (particularly with code first)?

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  • how to made one-to-one bidirectional relationships in grails?

    - by user369759
    I have two domain classes and want to have one-to-one BIDIRECTIONAL relation between them. I write: class Person { Book book; String name Integer age Date lastVisit static constraints = { book unique: true // "one-to-one". Without that = "Many-to-one". } } class Book { String title Date releaseDate String ISBN static belongsTo = [person:Person] // it makes relationship bi-directional regarding the grails-docs } So, i want to have bi-directional, i could NOT find link from Book to Person in generated SQL: CREATE TABLE `book` ( `id` bigint(20) NOT NULL AUTO_INCREMENT, `version` bigint(20) NOT NULL, `isbn` varchar(255) NOT NULL, `release_date` datetime NOT NULL, `title` varchar(255) NOT NULL, PRIMARY KEY (`id`) ) ENGINE=MyISAM AUTO_INCREMENT=2 DEFAULT CHARSET=latin1 So then it means it is not bidirectional then? How to make bidirectional?

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  • How do I do a count on that meet a specific condition, dependent on several has_many relationships i

    - by Angela
    I have a Model Campaign. A Campaign has many Events. Each Event has an attribute :days. A Campaign also has_many Contacts. Each Contact as a :date_entered attribute. The from_today(contact,event) method returns a number, which is the number of days from the contact's :date_entered till today minus the event's :days. In other words, a positive number shows the number of days from today till the :days of the event is elapsed. If it is negative, if means that the number of days that has elapsed since the :date_entered is greater than the :days attribute of an event. In other words, the event is overdue. What I would like to be able to do is do campaign.overdue and this would result in a total number of contacts that have an overdue event. It shouldn't count multiple events for a single contact, just one contact. How do I do that? It seems like I would need to cycle through all the events for every contact and keep a counter but I'm assuming that there is a better way.

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  • Looking for an issue tracker / project management software that automatically manages start/completion dates based on priority/relationships

    - by user361910
    So, a little background. We are a small company with a half-dozen developers. We have been evaluating many project management / issue tracking software packages (TRAC, Redmine, FogBugz, etc) and trying to create a decent process/workflow for managing projects, adding features, fixing bugs, etc. I'd like to think our requirements are similar to most other companies our size. Essentially, what this comes down to is 1) An easy way for the PM and developers to track projects, issues, bugs, etc 2) An easy way for the PM and admin/executives to get a birds-eye view of progress and easily manage timelines, schedules, and priorities. After trying TRAC, we moved to Redmine. We found Redmine to be easier than track to administer and the ability to have sub-projects and sub-tickets is great. However, the big problem we ran into is the fact that it is very difficult to manage schedules and timelines. It seems like it would be incredibly time-intensive to manage because you have to manually enter a start date, estimated time, and end date for each ticket, project, etc. So if you setup a month's schedule based on priorities, what are you supposed to do when a particular ticket/issue/subproject takes up more time than was estimated. Right now, it appears I would have to go back in and MANUALLY change the start/end date of every single item. What would be ideal is to be able to set priorities/dependencies and estimated time on tickets/milestones, and have the software automatically manage the start/end dates. Does anyone know how to get Redmine to do this, or recommend a different software package that can do something like this!

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  • Why does Perl allow mutual "use" relationships between modules?

    - by Haiyuan Zhang
    Let's say there are two modules that mutually use each other: package a; use b; sub p {} 1; package b; use a; 1; I think that it is systematically wrong to write code like the above, because the two modules will endlessly copy each other's code to themselves, but I can successfully run the following code, which makes me very surprised. Could any of you explain all of this to me? #! /usr/bin/perl use a; a->p();

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  • I can't understand GroupJoin where i will need it in database relationships.

    - by Freshblood
    Hello Everybody I am thinking 5-6 hours to understand something about GroupJoin. I am talking about query with linq for Database tables.I understand what Join and GroupJoin does but I really couldn't understand where i will need it.I feel that Join does all what i will need but if there is something which Join can't without GroupJoin so i feel that situation is meaningless or useless. For example: Persons table in relation with Phones and Phones table hold foreign keys of Persons and one person can have one more phone number.If we want to brings all persons who has phone numbers and who hasn't too so we will need GroupJOin but what for we will need this query ? Can u give me good reason , example or explenation for using GroupJoin ?

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