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  • Building a wiki like data model in rails question.

    - by lillq
    I have a data model in which I would like to have an item that has a description that can be edited. I would like to also keep track of all edits to the item. I am running into issues with my current strategy, which is: class Item < ActiveRecord::Base has_one :current_edit, :class_name => "Edit", :foreign_key => "current_edit_id" has_many :edits end class Edit < ActiveRecord::Base belongs_to :item end Can the Item have multiple associations to the same class like this? I was thinking that I should switch to keeping track of the edit version in the Edit object and then just sorting the has_many relationship base on this version.

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  • How to specify a different column for a @Inheritance JPA annotation

    - by Cue
    @Entity @Inheritance(strategy = InheritanceType.JOINED) public class Foo @Entity @Inheritance(strategy = InheritanceType.JOINED) public class BarFoo extends Foo mysql> desc foo; +---------------+-------------+ | Field | Type | +---------------+-------------+ | id | int | +---------------+-------------+ mysql> desc barfoo; +---------------+-------------+ | Field | Type | +---------------+-------------+ | id | int | | foo_id | int | | bar_id | int | +---------------+-------------+ mysql> desc bar; +---------------+-------------+ | Field | Type | +---------------+-------------+ | id | int | +---------------+-------------+ Is it possible to specify column barfo.foo_id as the joined column? Are you allowed to specify barfoo.id as BarFoo's @Id since you are overriding the getter/seeter of class Foo? I understand the schematics behind this relationship (or at least I think I do) and I'm ok with them. The reason I want an explicit id field for BarFoo is exactly because I want to avoid using a joined key (foo _id, bar _id) when querying for BarFoo(s) or when used in a "stronger" constraint. (as Ruben put it)

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  • Doctrine: Relating a model to itself using a link table, like "This event is related to to the following other events"

    - by mattalexx
    So in English, the relationship would sound like "This event is related to to the following other events". My first instinct is to create an EventEvent model, with a first_event_id field and a second_event_id field. Then I would define the following two relationships in the Event model: $this->hasMany('Event as FirstRelatedEvents', array('local' => 'first_event_id', 'foreign' => 'second_event_id', 'refClass' => 'EventEvent')); $this->hasMany('Event as SecondRelatedEvents', array('local' => 'second_event_id', 'foreign' => 'first_event_id', 'refClass' => 'EventEvent')); But I would rather not have to use two relationships on the Event model. Is there a better way to do this?

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  • Rails 3: habtm migration, primary key issue

    - by Brian Wigginton
    I'm trying to setup a migration file for a habtm relationship, however when I run the migration I'm getting the following error: Primary key is not allowed in a has_and_belongs_to_many join table (parts_vehicles). Here is my migration file (20110111035950_create_parts_vehicles.rb): class CreatePartsVehiclesJoinTable < ActiveRecord::Migration def self.up create_table :parts_vehicles, :id => false do |t| t.integer :part_id t.integer :vehicle_id end end def self.down drop_table :parts_vehicles end end The documentation example states to use :id => false to disable a primary key from being generated, but I'm still getting the error.

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  • SubSonic isn't generating MySql foreign key tables

    - by keith
    I two tables within a MySql 5.1.34 database. When using SubSonic to generate the DAL, the foreign-key relationship doesn't get scripted, ie; I have no Parent.ChildCollection object. Looking inside the generated DAL Parent class shows the following; //no foreign key tables defined (0) I have tried SubSonic 2.1 and 2.2, and various MySql 5 versions. I must be doing something wrong procedurally - any help would be greatly appreciated. This has always just worked 'out-the-box' when using MS-SQL. TABLE `parent` ( `ParentId` INT(11) NOT NULL AUTO_INCREMENT, `SomeData` VARCHAR(25) DEFAULT NULL, PRIMARY KEY (`ParentId`) ) ENGINE=INNODB DEFAULT CHARSET=latin1; TABLE `child` ( `ChildId` INT(11) NOT NULL AUTO_INCREMENT, `ParentId` INT(11) NOT NULL, `SomeData` VARCHAR(25) DEFAULT NULL, PRIMARY KEY (`ChildId`), KEY `FK_child` (`ParentId`), CONSTRAINT `FK_child` FOREIGN KEY (`ParentId`) REFERENCES `parent` (`ParentId`) ) ENGINE=INNODB DEFAULT CHARSET=latin1;

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  • Rails belongs_to issue in the views

    - by Jacobo Tibaquira
    Hi, Im having problems with an association in rails: Currently I have Post and User models, and the relationship is set this way: class User < ActiveRecord::Base attr_accessible :username, :name, :lastname has_many :posts end class Post < ActiveRecord::Base attr_accessible :title, :body belongs_to :user end However, in my app/views/posts/index.html.haml when Im trying to access the username for the post I get this error: undefined method `name' for nil:NilClass This is my view: - title "Posts" %table %tr %th Title %th Body %th Author - for post in @posts %tr %td= h post.title %td= h post.body %td= h post.user.name %td= link_to 'Show', post %td= link_to 'Edit', edit_post_path(post) %td= link_to 'Destroy', post, :confirm => 'Are you sure?', :method => :delete %p= link_to "New Post", new_post_path Any thoughts of what Im doing wrong will be appretiated

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  • In CouchDB, how to get documents limited on value in related document? In terms of SQL, how to make WHERE on JOINed table

    - by amorfis
    Crossposting from [email protected] Assume we have two kind of documents in CouchDB. Person and Car: Person: _id firstname surname position salary Car: _id person_id reg_number brand So there is one to many relationship. One person can have many cars. I can construct map function to get every person and his/her car next to each other. In such case key is array [person.id, 0] and [car.person_id, 1]. What I can't do, is limiting this view to owners of specific brand only, e.g. if I need salaries of owners of Ferrari.

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  • SQL to get friends AND friends of friends of a user

    - by Enrique
    My MySQL tables structure is like this. USER int id varchar username FRIEND_LIST int user_id int friend_id For each friend relationship I insert 2 records in FRIEND_LIST. If user 1 is friend of user 2 then the next rows are inserted into FRIEND_LIST 1,2 2,1 I want to get the friends and friends of friends of an specific user. The select should return columns a, b, c. a: user_id b: friend_id c: username (username of friend_id ) If 1 is friend of 2 and 3. 2 is friend of 3, 4 and 5 3 is friend of 5,6,7 Then the query to get 1's friends and friends of friends should return: 1 2 two 1 3 three 2 1 one 2 3 three 2 4 four 2 5 five 3 1 one 3 5 five 3 6 six 3 7 seven Can I get this rows with a single query?

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  • MySQL Many to Many with Unique keys and Update/Select if Exists otherwise Insert

    - by Jayrox
    In my goal to have a Many-to-Many relationship in my MySQL database I have arrived at another bridge to build. Current Tables: Users (id, name) Tags (id, name) User_Tags (user_id, tag_id) Here is the goal: I would like to have the ability to take a tag i.e: #fb and insert it into my Tags database which has a unique constraint on name and if the tag exists I would like to return it's id I would like to insert the tag.id and the current user's user.id into User_Tags. I do not have any unique constraints on the User_Tags table because I would like to be able to track the user's most commonly used tags and present them in a list ordered by frequency of use. I am currently developing this project in PHP using prepared statements. Additionally, performance is not currently an issue as my user count is still fairly small, but it is steadily growing and may be an issue in the future.

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  • CPU Usage relative to number of users? - ASP.Net Application

    - by soldieraman
    My Asp.net application uses 25-30% of the CPU on a test server which has 600 MB Ram on it. I can see the asp_wb process taking that much percentage of CPU. This is when I am testing using one user. How many users can the server afford then without falling over? Is there a relationship between the CPU Usage and number of user aka if there are 2 users my application will sky rocket to 60% of memory usage? Or does/Should/How does the server handle this?

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  • CakePHP HABTM Plugin table naming conventions (for 1.3)

    - by Parris
    Hi everyone, I know naming conventions for tables used by plugins generally start with the name of the plugin and then the model pluralized. For example lets say I had a plugin called Poll, with a model also called PollPoll and another model called PollTag then the resulting table names would be poll_polls and poll_tags. They would also have a habtm relationship so what is the convention for that table name? I believe it would poll_poll_polls_poll_tags, although it is a little redundant it makes sense since the first poll_ represents the name of the plugin, while poll_polls and poll_tags relates to the models. Also have any naming conventions changed for plugins in 1.3? Is the above stated correct? Thanks!

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  • What is the initiating actor for the usecase shown here

    - by Illep
    I am new to drawing use case and writing use case descriptions. I have an Actor called User , an abstract usecase called Work Type and another use case called Manager. The usecase Manager has a generalized relationship with the Work Type use case. I'm now writing the use case description for Manager use case. And what is the initiating Actor for this use case. Is it the Actor User ? or doesn't it have an initiating Actor ? Note: I only want to know the initiating Actor for the use case Manager

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  • Core Data Predicate To Many

    - by Vikings
    I have a core data model that has a one to many relationship, there is a category, and it can contain many subcategories. Category <---- Subcategory I am trying to perform a fetch that checks if a particular Category contains a Subcategory with a particular name. Let's say I have two categories below, I want to fetch to see if there are any subcategories name "Apple" in the Category named "Fruits". Vetegables - Carrot - Lettuce Fruits - Apple - Orange - Pear Code: - (SubCategory *)searchForSubCategoryWithName:(NSString *)subCategory inCategory:(Category *)category { NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init]; NSEntityDescription *entity = [NSEntityDescription entityForName:@"SubCategory" inManagedObjectContext:self.beer.managedObjectContext]; [fetchRequest setEntity:entity]; NSPredicate *predicate = [NSPredicate predicateWithFormat:@"name == [c] %@", subCategory]; [fetchRequest setPredicate:predicate]; NSError *error; NSArray *fetchedObjects = [self.beer.managedObjectContext executeFetchRequest:fetchRequest error:&error]; if (fetchedObjects != nil && fetchedObjects.count > 0) { return [fetchedObjects objectAtIndex:0]; } else { return nil; } }

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  • Physical Cores vs Virtual Cores in Parallelism

    - by Code Curiosity
    When it comes to virtualization, I have been deliberating on the relationship between the physical cores and the virtual cores, especially in how it effects applications employing parallelism. For example, in a VM scenario, if there are less physical cores than there are virtual cores, if that's possible, what's the effect or limits placed on the application's parallel processing? I'm asking, because in my environment, it's not disclosed as to what the physical architecture is. Is there still much advantage to parallelizing if the application lives on a dual core VM hosted on a single core physical machine?

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  • Displaying User Relationships Module Blocks

    - by Bob Lerner
    I'm unable to display any of the User Relationships' auto-created blocks in any of my sidebars. I have tried enabling all modules and permissions I can think of, with no success. The block I'm most interested in is the block that would allow users to be invited to an existing relationship (e.g. Friend), but as I say this nor any of the other blocks display. Other Drupal blocks and custom blocks display just fine. The blocks do show up in the blocks listing, and I've tried different ways of configuring them. Any help, or even confirmation that someone has been able to do this with the latest stable versions of Drupal and the User Relationships module, would be appreciated. Thank you.

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  • Looking for an algorithm in vb.net or c# but I don't know it's name!

    - by Jules
    I'll do my best to explain what the algorithm is supposed to do: There's a class 'Recipe'. Each Recipe can include other Recipes but cannot include itself or any other Recipe that includes it. So, a simple example is we have just two Recipes A & B. If A adds B first, then later on B cannot add A because it will cause a loop. A more complicated example is: A,B,C (1) Recipe C Adds B (2) Recipe B Adds A (3) Recipe A attempts to add C, but can't because of the relationship. C - B - A. I can do this myself, I just wondered if this was a standard named algorithm and I could grab the optimal solution. Thanks

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  • How to select elements from a set that are children of another element

    - by Tatu Ulmanen
    Hi, The title is a bit confusing but here's what I'm after: I have a set of elements containing all the h3 elements in a page. In jQuery terms: var mySet = $('h3'). I also have an div element var myContainer = $('div#foo') I need to find all items in the set mySet that are children of myContainer. Any ideas? I bet there's some magical one liner for this but I cannot think of any. I'd rather not loop through every element in the set manually and use .closest(myContainer) or something like that to determine the relationship. Note that in my scenario, I cannot use a new selector like $('div#foo h3') (that would be too easy) as I don't have access to the actual selector values. So it has to be dynamic.

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  • Ruby on Rails updating join table records

    - by Eef
    Hey, I have two models Users and Roles. I have setup a many to many relationship between the two models and I have a joint table called roles_users. I have a form on a page with a list of roles which the user checks a checkbox and it posts to the controller which then updates the roles_users table. At the moment in my update method I am doing this because I am not sure of a better way: role_ids = params[:role_ids] user.roles.clear role_ids.each do |role| user.roles << Role.find(role) end unless role_ids.nil? So I am clearing all the entries out then looping threw all the role ids sent from the form via post, I also noticed that if all the checkboxes are checked and the form posted it keeps adding duplicate records, could anyone give some advice on a more efficent way of doing this?

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  • MySQL foreign key constraints, cascade delete

    - by Cudos
    Hello. I want to use foreign keys to keep the integrity and avoid orphans (I already use innoDB). How do I make a SQL statment that DELETE ON CASCADE? Secondly, that using DELETE ON CASCADE. E.g. if I delete a category then it would delete products related to that category even though there are other categories related to those products. The pivot table "categories_products" creates a many-to-many relationship between the two other tables. categories - id (INT) - name (VARCHAR 255) products - id - name - price categories_products - categories_id - products_id

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  • Entity Framework: Setting EntityReference EntityKey causes exception on save

    - by NYSystemsAnalyst
    I have a table with a ModifiedUserID field that is a foreign key to a User table. In entity framework, I'm loading the first table, but not the users table. I have the user ID of the current user, and would like to set the ModifiedUserID to that value for all entities that have been modified prior to saving. Before calling SaveChanges(), I use the ObjectStateManager to get all modified entities. Since I do not have the user object, but I do have the user ID, I set the EntityReference.EntityKey property as follows: entity.UserReference.EntityKey = New EntityKey("MyContainer.User", "UserID", DatabaseUserID) This works fine, but when I execute SaveChanges(), I receive the following error: A relationship is being added or deleted from an AssociationSet 'FK_Table1_User'. With cardinality constraints, a corresponding 'Table1' must also be added or deleted. Now, I see that setting the EntityReference.EntityKey creates a new AssociationSet entry, but how to I prevent this error?

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  • Does SQL Server 2005 error message numbers back to the asp.net application?

    - by Duke
    I'd like to get the message number and severity level information from SQL Server upon execution of an erroneous query. For example, when a user attempts to delete a row being referenced by another record, and the cascade relationship is "no action", I'd like the application to be able to check for error message 547 ("The DELETE statement conflicted with the REFERENCE constraint...") and return a user friendly and localized message to the user. When running such a query directly on SQL Server, the following message is printed: Msg 547, Level 16, State 0, Line 1 <Error message...> In an Asp.Net app is this information available in an event handler parameter or elsewhere? Also, I don't suppose anyone knows where I can find a definitive reference of SQL Server message numbers?

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  • Best practice in Rails when editing scaffold made pages

    - by abegbg
    I have a best practice question. I have two classes, company and category. They have a many-to-many relationship. When clicking a category I shall go to a page showing all companies with the chosen category. Pretty straight forward. My question is: Should I list all the companies on the companies/index.html.erb after filtering the companies in the controller? or Should I list all the companies on the categories/show.html.erb page? or Should I do a completely new page, since it doesn't really fit into any of the two above? Do you generally make a new page when your goal doesn't fit the scaffold made pages or do you use them quite freely? I am working/learning alone with rails, so there are a lot of best practice questions popping up all the time. Cheers Carl

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  • How do I find the user that has both a cat and a dog?

    - by brad
    I want to do a search across 2 tables that have a many-to-one relationship, eg class User << ActiveRecord::Base has_many :pets end class Pet << ActiveRecord::Base belongs_to :users end Now let's say I have some data like so users id name 1 Bob 2 Joe 3 Brian pets id user_id animal 1 1 cat 2 1 dog 3 2 cat 4 3 dog What I want to do is create an active record query that will return a user that has both a cat and a dog (i.e. user 1 - Bob). My attempt at this so far is User.joins(:pets).where('pets.animal = ? AND pets.animal = ?','dog','cat') Now I understand why this doesn't work - it's looking for a pet that is both a dog and a cat so returns nothing. I don't know how to modify this to give me the answer I want however. Does anyone have any suggestions? This seems like it should be easy - it doesn't seem like an especially unusual situation.

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  • PHP/MySQL: Check if something 'belongs-to' something else?

    - by Nebs
    I have two tables: Stores and Items. The relationship is: Stores 1---* Items In PHP/MySQL what would be the best (fastest/simplest) way to check if a particular item belongs to a particular store. In other words given for example: $store_id = 1; $item_id = 12; I want to check if item 12 belongs to store 1 (and not some other store). I usually do a select on Items matching both the store_id and item_id and limit the results to 1. Then check how many rows (0 or 1) were returned with mysql_num_rows. Is there a better way? Update: Both tables have an "id" column. The Items table has a "store_id" column.

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  • Parent-Child relation while using object data source

    - by Saba
    Hello guys I am experiencing with a class generator I've written, which generates a class for each table in database with each table field as a property and such. Before that, I used to add a typed dataset to the project and add some tables to it. It automatically detected the relationship between tables and when I added a parent table as data source of a datagrid, I could add another datagrid and use the foreing key data member of it's bindingsource to fill it, and when someone moved the focus on parent datagrid, the data in child datagrid would change accordingly. Now that I have my classes, I add an object as data source for my 2 datagrids, but obviously it doesn't detect a parent child relation. But It'd really help if I could have that foreign key relation in my object datasources. Is there any way to have that relation in object datasource?

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