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  • How do I create and use a junction table in Rails?

    - by Thierry Lam
    I have the following data: A post called Hello has categories greet Another post called Hola has categories greet, international My schema is: create_table "posts", :force => true do |t| t.string "name" t.datetime "created_at" t.datetime "updated_at" end create_table "categories", :force => true do |t| t.string "name" t.datetime "created_at" t.datetime "updated_at" end create_table "posts_categories", :force => true do |t| t.integer "post_id" t.integer "category_id" t.datetime "created_at" t.datetime "updated_at" end After reading the Rails guide, the most suitable relationship for the above seems to be: class Post < ActiveRecord::Base has_and_belongs_to_many :categories end class Category < ActiveRecord::Base has_and_belongs_to_many :posts end My junction table also seems to have a primary key. I think I need to get rid of it. What's the initial migration command to generate a junction table in Rails? What's the best course of action, should I drop posts_categories and re-create it or just drop the primary key column? Does the junction table have a corresponding model? I have used scaffold to generate the junction table code, should I get rid of the extra code? Assuming all the above has been fixed and is working properly, how do I query all posts and display them along with their named categories in the view. For example: Post #1 - hello, categories: greet Post #2 - hola, categories: greet, international

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  • iPhone and Core Data: how to retain user-entered data between updates?

    - by Shaggy Frog
    Consider an iPhone application that is a catalogue of animals. The application should allow the user to add custom information for each animal -- let's say a rating (on a scale of 1 to 5), as well as some notes they can enter in about the animal. However, the user won't be able to modify the animal data itself. Assume that when the application gets updated, it should be easy for the (static) catalogue part to change, but we'd like the (dynamic) custom user information part to be retained between updates, so the user doesn't lose any of their custom information. We'd probably want to use Core Data to build this app. Let's also say that we have a previous process already in place to read in animal data to pre-populate the backing (SQLite) store that Core Data uses. We can embed this database file into the application bundle itself, since it doesn't get modified. When a user downloads an update to the application, the new version will include the latest (static) animal catalogue database, so we don't ever have to worry about it being out of date. But, now the tricky part: how do we store the (dynamic) user custom data in a sound manner? My first thought is that the (dynamic) database should be stored in the Documents directory for the app, so application updates don't clobber the existing data. Am I correct? My second thought is that since the (dynamic) user custom data database is not in the same store as the (static) animal catalogue, we can't naively make a relationship between the Rating and the Notes entities (in one database) and the Animal entity (in the other database). In this case, I would imagine one solution would be to have an "animalName" string property in the Rating/Notes entity, and match it up at runtime. Is this the best way to do it, or is there a way to "sync" two different databases in Core Data?

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  • Programming test for ASP.NET C# developer job - Opinions please!

    - by Indy
    Hi all, We are hiring a .NET C# developer and I have developed a technical test for the candidates to complete. They have an hour and it has two parts, some knowledge based questions covering asp.net, C# and SQL and a small practical test. I'd appreciate feedback on the test, is it sufficient to test the programmers ability? What would you change if anything? Part One. What the are events fired as part of the ASP.NET Page lifecycle. What interesting things can you do at each? How does ViewState work and why is it either useful or bad? What is a common way to create web services in ASP.NET 2.0? What is the GAC? What is boxing? What is a delegate? The C# keyword .int. maps to which .NET type? Explain the difference between a Stored Procedure and a Trigger? What is an OUTER Join? What is @@IDENTITY? Part Two: You are provided with the Northwind Database and the attached DB relationship diagram. Please create a page which provides users with the following functionality. You don’t need to be too concerned with the presentation detail of the page. Select a customer from a list, and see all the orders placed by that customer. For the same customer, find all their orders which are Beverages and the quantity is more than 5. I was aware of setting the right balance of difficulty on this as there is an hour's test. I was able to complete the practical test in under 30 mins using SQLDatasource and the query designer in visual studio and the test questions, I am looking to see how they approach it logically and whether they use the tools available. Many thanks!

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  • org.hibernate.hql.ast.QuerySyntaxException: TABLE NAME is not mapped

    - by Coronatus
    I have two models, Item and ShopSection. They have a many-to-many relationship. @Entity(name = "item") public class Item extends Model { @ManyToMany(cascade = CascadeType.PERSIST) public Set<ShopSection> sections; } @Entity(name = "shop_section") public class ShopSection extends Model { public List<Item> findActiveItems(int page, int length) { return Item.find("select distinct i from Item i join i.sections as s where s.id = ?", id).fetch(page, length); } } findActiveItems is meant to find items in a section, but I get this error: org.hibernate.hql.ast.QuerySyntaxException: Item is not mapped [select distinct i from Item i join i.sections as s where s.id = ?] at org.hibernate.hql.ast.util.SessionFactoryHelper.requireClassPersister(SessionFactoryHelper.java:180) at org.hibernate.hql.ast.tree.FromElementFactory.addFromElement(FromElementFactory.java:111) at org.hibernate.hql.ast.tree.FromClause.addFromElement(FromClause.java:93) at org.hibernate.hql.ast.HqlSqlWalker.createFromElement(HqlSqlWalker.java:322) at org.hibernate.hql.antlr.HqlSqlBaseWalker.fromElement(HqlSqlBaseWalker.java:3441) at org.hibernate.hql.antlr.HqlSqlBaseWalker.fromElementList(HqlSqlBaseWalker.java:3325) at org.hibernate.hql.antlr.HqlSqlBaseWalker.fromClause(HqlSqlBaseWalker.java:733) at org.hibernate.hql.antlr.HqlSqlBaseWalker.query(HqlSqlBaseWalker.java:584) at org.hibernate.hql.antlr.HqlSqlBaseWalker.selectStatement(HqlSqlBaseWalker.java:301) at org.hibernate.hql.antlr.HqlSqlBaseWalker.statement(HqlSqlBaseWalker.java:244) at org.hibernate.hql.ast.QueryTranslatorImpl.analyze(QueryTranslatorImpl.java:254) at org.hibernate.hql.ast.QueryTranslatorImpl.doCompile(QueryTranslatorImpl.java:185) at org.hibernate.hql.ast.QueryTranslatorImpl.compile(QueryTranslatorImpl.java:136) at org.hibernate.engine.query.HQLQueryPlan.<init>(HQLQueryPlan.java:101) at org.hibernate.engine.query.HQLQueryPlan.<init>(HQLQueryPlan.java:80) at org.hibernate.engine.query.QueryPlanCache.getHQLQueryPlan(QueryPlanCache.java:124) at org.hibernate.impl.AbstractSessionImpl.getHQLQueryPlan(AbstractSessionImpl.java:156) at org.hibernate.impl.AbstractSessionImpl.createQuery(AbstractSessionImpl.java:135) at org.hibernate.impl.SessionImpl.createQuery(SessionImpl.java:1770) at org.hibernate.ejb.AbstractEntityManagerImpl.createQuery(AbstractEntityManagerImpl.java:272) ... 8 more What am I doing wrong?

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  • How can i ignore map property in NHibernate with setter

    - by Emilio Montes
    i need ignore map property with setter in NHibernate, because the relationship between entities is required. this is my simple model public class Person { public virtual Guid PersonId { get; set; } public virtual string FirstName { get; set; } public virtual string SecondName { get; set; } //this is the property that do not want to map public Credential Credential { get; set; } } public class Credential { public string CodeAccess { get; set; } public bool EsPremium { get; set; } } public sealed class PersonMap : ClassMapping<Person> { public PersonMap() { Table("Person"); Cache(x => x.Usage(CacheUsage.ReadWrite)); Id(x => x.Id, m => { m.Generator(Generators.GuidComb); m.Column("PersonId"); }); Property(x => x.FirstName, map => { map.NotNullable(true); map.Length(255); }); Property(x => x.SecondName, map => { map.NotNullable(true); map.Length(255); }); } } I know that if I leave the property Credential {get;} I was not going to take the map of NHibernate, but I need to set the value. Thanks in advance.

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  • Validation not bubbling up to my other models.

    - by DJTripleThreat
    Ok, I have a relationship between People, Users and Employees such that All Employees are Users and all Users are People. Person is an abstract class that User is derived from and Employee is derived from that. Now... I have an EmployeesController class and the create method looks like this: def create @employee = Employee.new(params[:employee]) @employee.user = User.new(params[:user]) @employee.user.person = Person.new(params[:person]) respond_to do |format| if @employee.save flash[:notice] = 'Employee was successfully created.' format.html { redirect_to(@employee) } format.xml { render :xml => @employee, :status => :created, :location => @employee } else format.html { render :action => "new" } format.xml { render :xml => @employee.errors, :status => :unprocessable_entity } end end end As you can see, when I'm using the :polymorphic => true clause, the way you access the super class is by doing something like @derived_class_variable.super_class_variable.super_super_etc. The Person class has a validates_presence_of :first_name and when it is satisfied, on my form, everything is OK. However, if I leave out the first name, it won't prevent the employee from being saved. What happens is that the employee record is saved but the person record isn't (because of the validation). How can I get the validation errors to show up in the flash object?

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  • How to insert an Array/Objet into SQL (bestpractice)

    - by Jason
    I need to store three items as an array in a single column and be able to quickly/easily modify that data in later functions. [---YOU CAN SKIP THIS PART IF YOU TRUST ME--] To be clear, I love and use x_ref tables all the time but an x_ref doesn't work here because this is not a one-to-many relationship. I am making a project management tool that among other things, assigns a user to a project and assigns hours to that project on a weekly basis, per user, sometimes for weeks many weeks into the future. Of course there are many projects, a project can have many team members, a team member can be involved with many projects at one time BUT its not one-to-many because a team member can be working many weeks on the same project but have different hours for different weeks. In other words, each object really is unique. Also/finally, this data can be changed at any time by any team-member - hence it needs to be easily to manipulate. Basically, I need to handle three values (the team member, the week we're talking about, and how many hours) dropped into a project row in the projects table (under the column for project team members) and treated as one item - a team member - that will actually be part of a larger array of all the team members involved on the project. [--END SKIP, START READING HERE :) --] So assuming that the application's general schema and relation tables aren't total crap and that we are in fact up against a wall in this one case to use an array/object as a value for this column, is there a best practice for that? Like a particular SQL data-type? A particular object/array format? CSV? JSON? XML? Most of the app is in C# but (for very odd reasons that I won't explain) we could really use any environment if there is a particular one that handles this well. For the moment, I am thinking either (webservice + JS/JSON) or PHP unserialize/serialize (but I am bit sketched out by the PHP solution because it seems a bit cumbersome when using ajax?) Thoughts anyone?

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  • Why should I bother with unit testing if I can just use integration tests?

    - by CodeGrue
    Ok, I know I am going out on a limb making a statement like that, so my question is for everyone to convince me I am wrong. Take this scenario: I have method A, which calls method B, and they are in different layers. So I unit test B, which delivers null as a result. So I test that null is returned, and the unit test passes. Nice. Then I unit test A, which expects an empty string to be returned from B. So I mock the layer B is in, an empty string is return, the test passes. Nice again. (Assume I don't realize the relationship of A and B, or that maybe two differente people are building these methods) My concern is that we don't find the real problem until we test A and B togther, i.e. Integration Testing. Since an integration test provides coverage over the unit test area, it seems like a waste of effort to build all these unit tests that really don't tell us anything (or very much) meaningful. Why am I wrong?

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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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  • Saving a record in Authlogic table

    - by denniss
    I am using authlogic to do my authentication. The current model that serves as the authentication model is the user model. I want to add a "belongs to" relationship to user which means that I need a foreign key in the user table. Say the foreign key is called car_id in the user's model. However, for some reason, when I do u = User.find(1) u.car_id = 1 u.save! I get ActiveRecord::RecordInvalid: Validation failed: Password can't be blank My guess is that this has something to do with authlogic. I do not have validation on password on the user's model. This is the migration for the user's table. def self.up create_table :users do |t| t.string :email t.string :first_name t.string :last_name t.string :crypted_password t.string :password_salt t.string :persistence_token t.string :single_access_token t.string :perishable_token t.integer :login_count, :null => false, :default => 0 # optional, see Authlogic::Session::MagicColumns t.integer :failed_login_count, :null => false, :default => 0 # optional, see Authlogic::Session::MagicColumns t.datetime :last_request_at # optional, see Authlogic::Session::MagicColumns t.datetime :current_login_at # optional, see Authlogic::Session::MagicColumns t.datetime :last_login_at # optional, see Authlogic::Session::MagicColumns t.string :current_login_ip # optional, see Authlogic::Session::MagicColumns t.string :last_login_ip # optional, see Authlogic::Session::MagicColumns t.timestamps end end And later I added the car_id column to it. def self.up add_column :users, :user_id, :integer end Is there anyway for me to turn off this validation?

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  • How can use the currently displayed node to filter a block-level view on that node's page?

    - by Deane
    I have parent/child relationship set up via Node Reference. A Child record can have a Parent record selected from a Node Reference field (this is optional -- I can have Parent-less Children as well). I've created a Views block to appear on the Parent pages, below the content. It's going to show a table of all the Child nodes for that Parent. Problem is, right now it shows every Child node. I need to filter it for just the Parent being displayed. What I need to be able to do is add a filter to this View to effectively say, "Only show the Child nodes that are assigned to the Parent being displayed on this page." So, somehow I need to be able to get the Nid of the currently displaying node (which will be a Parent, in all cases when this block is displayed), and use that in a filter in my View. How exactly can I do this? (Initially I used an attachment view for this (as this page instructs). I created a page view to display the Parent, then an attachment view to display all the Children, then attached that under the page view. This worked, but it was almost absurdly complicated to set up, and it was an undesirable for a number of other reasons -- primarily that my Parent now has two dedicated URLs, it's own node-level page, and the similar page created by this view.) Using Drupal 6.15.

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  • Avoiding Duplicate Data in DB (for use with Rails)

    - by ants
    I have five tables that I am trying to get to work nicely together but may need some help. I have three main tables: accounts members and roles. With two join tables account_members and account_member_roles. The accounts and members table are joined by account_members (fk account_id and member_id) table. The other 2 tables are the problem (roles and account_member_roles). A member of an account can have more than one role and I have the account_member_roles (fk account_member_id and role_id) table joining the account_members join table and the roles table. That seems logical but can you have a relationship with a join table? What I'd like to be able to do is when creaeting an account, for instance, I would like @account.save to include the roles and update the account_member_roles table neatly ..... but through the account_members join table. I've tried ..... accept_nested_attributes_for :members, :account_member_roles in the account.rb but I get ..... ActiveRecord::HasManyThroughCantAssociateThroughHasManyReflection (Cannot modify association 'Account#account_member_roles' because the source reflection class 'AccountMemberRole' is associated to 'AccountMember' via :has_many.) upon trying to save a record. Any advice on how I should approach this? CIA -ants

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  • Entity Framework 4 / POCO - Where to start?

    - by Basiclife
    Hi, I've been programming for a while and have used LINQ-To-SQL and LINQ-To-Entities before (although when using entities it has been on a Entity/Table 1-1 relationship - ie not much different than L2SQL) I've been doing a lot of reading about Inversion of Control, Unit of Work, POCO and repository patterns and would like to use this methodology in my new applications. Where I'm struggling is finding a clear, concise beginners guide for EF4 which doesn't assume knowledge of EF1. The specific questions I need answered are: Code first / model first? Pros/cons in regards to EF4 (ie what happens if I do code first, change the code at a later date and need to regenerate my DB model - Does the data get preserved and transformed or dropped?) Assuming I'm going code-first (I'd like to see how EF4 converts that to a DB schema) how do I actually get started? Quite often I've seen articles with entity diagrams stating "So this is my entity model, now I'm going to ..." - Unfortunately, I'm unclear if they're created the model in the designer, saved it to generate code then stopped any further auto-code generation -or- They've coded (POCO)? classes and the somehow imported them into the deisgner view? I suppose what I really need is an understanding of where the "magic" comes from and how to add it myself if I'm not just generating an EF model directly from a DB. I'm aware the question is a little vague but I don't know what I don't know - So any input / correction / clarification appreciated. Needless to say, I don't expect anyone to sit here and teach me EF - I'd just like some good tutorials/forums/blogs/etc. for complete entity newbies Many thanks in advance

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  • Django m2m form appearing fields

    - by dana
    I have a classroom application,and a follow relation. Users can follow each other and can create classrooms.When a user creates a classroom, he can invite only the people that are following him. The Classroom model is a m2m to User table. i have in models. py: class Classroom(models.Model): creator = models.ForeignKey(User) classname = models.CharField(max_length=140, unique = True) date = models.DateTimeField(auto_now=True) open_class = models.BooleanField(default=True) members = models.ManyToManyField(User,related_name="list of invited members") and in models.py of the follow application: class Relations(models.Model): initiated_by = models.ForeignKey(User, editable=False) date_initiated = models.DateTimeField(auto_now=True, editable = False) follow = models.ForeignKey(User, editable = False, related_name = "follow") date_follow = models.DateTimeField(auto_now=True, editable = False) and in views.py of the classroom app: def save_classroom(request, username): if request.method == 'POST': u = User.objects.get(username=username) form = ClassroomForm(request.POST, request.FILES) if form.is_valid(): new_obj = form.save(commit=False) new_obj.creator = request.user r = Relations.objects.filter(initiated_by = request.user) # new_obj.members = new_obj.save() return HttpResponseRedirect('.') else: form = ClassroomForm() return render_to_response('classroom/classroom_form.html', { 'form': form, }, context_instance=RequestContext(request)) i'm using a ModelForm for the classroom form, and the default view, taking in consideration my many to many relation with User table, in the field Members, is a list of all Users in my database. But i only want in that list the users that are in a follow relationship with the logged in user - the one who creates the classroom. How can i do that? Thanks!

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  • Rails has_many conditions

    - by user305270
    c = "(f.profile_id = #{self.id} OR f.friend_id = #{self.id})" c += AND + "(CASE WHEN f.profile_id=#{self.id} THEN f.friend_id ELSE f.profile_id END = p.id)" c += AND + "(CASE WHEN f.profile_id=#{self.id} THEN f.profile_rejected ELSE f.friend_rejected END = 1)" c += AND + "(p.banned = 0)" I need this to be used in a has_many relationship like this: has_many :removed_friends, :conditions => ??? how do i set there the self.id?, or how do i pass there the id? Then i want to use the will_paginate plugin: @profile.removed_friends.paginate(:page => 1, :per_page => 20) Thanks for your help EDIT: class Profile < ActiveRecord::Base has_many :friendships has_many :removed_friends, :class_name => 'Profile', :through => :friendships, :conditions => "(friendships.profile_id = #{self.id} OR friendships.friend_id = #{self.id})" "AND (CASE WHEN friendships.profile_id=#{self.id} THEN friendships.profile_rejected ELSE friendships.friend_rejected END = 1)" + "AND (p.banned = 0)" end class Friendship < ActiveRecord::Base belongs_to :profile belongs_to :removed_friend, :class_name => 'Profile', :foreign_key => "(CASE WHEN friendships.profile_id = #{self.id} THEN friend_id ELSE profile_id END)" end

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  • Table cell in a split-view controller - selected cell becomes deselected when called by reloadData

    - by bpapa
    I'm working on a universal app that uses a SplitViewController to present a master-detail view. In the iPad HIG on Split Views, Apple states: In general, indicate the current selection in the left pane in a persistent way. This behavior helps people understand the relationship between the item in the left pane and the contents of the right pane. This is important because the contents of the right pane can change, but they should always remain related to the item selected in the left pane. So I'm trying to maintain selection state on the left. Easy enough when the user taps, I just remove the deselectRowAtIndexPath:animated: message from tableView:didSelectRowAtIndexPath: implementation. But, I also want the selection state to show up by default (without a user tap). I wound up putting this in my tableView:cellForRowAtIndexPath: implementation: if (UI_USER_INTERFACE_IDIOM() == UIUserInterfaceIdiomPad) { if (cellShouldBeSelected) cell.selected = YES; else cell.selected = NO; } The behavior I'm seeing, is that when the cells finall appear, for a fraction of a section the cell is indeed selected, but then the selection disappears without any user interaction. Any ideas? I set the new clearsSelectionOnViewWillAppear property to NO, but that doesn't seem to fix it, and it shouldn't really matter because I'm marking the cell as selected long after viewWillAppear is called - I'm actually doing it after some network activity and then sending the table view a reloadData message.

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  • Hibernate ManyToMany and superclass mapping problem

    - by Jesus Benito
    Hi all, I need to create a relation in Hibernate, linking three tables: Survey, User and Group. The Survey can be visible to a User or to a Group, and a Group is form of several Users. My idea was to create a superclass for User and Group, and create a ManyToMany relationship between that superclass and Survey. My problem is that Group, is not map to a table, but to a view, so I can't split the fields of Group among several tables -which would happen if I created a common superclass-. I thought about creating a common interface, but mapping to them is not allowed. I will probably end up going for a two relations solution (Survey-User and Survey-Group), but I don't like too much that approach. I thought as well about creating a table that would look like: Survey Id | ElementId | Type ElementId would be the Group or UserId, and the type... the type of it. Does anyone know how to achieve it using hibernate annotations? Any other ideas? Thanks a lot

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  • .Net Architecture challenge: The Change-prone Frankestein Model

    - by SDReyes
    Good Morning SO! We've been scratching our heads with with this interesting scenario at the office, and we're anxious to hear your ideas and approaches: We have a database, whose schema is prone to changes -lets call it Prony-. (is used to store configuration parameters for embedded devices. so if the embedded devices guy need a new table, property or relationship for the model, he should be able to adapt the schema in a easy way -happens so often- ). Prony needs a web interface to create/edit its data. We have another database containing data that also need to be loaded to the devices, after making some transformations - lets call this one Oddy- (this data it's generated by an already existent administrative web application). Finally we have Tracy, a server that communicates our DBs and our embedded devices. She should to auto-adapt herself, to our dbs schema changes and serialize the data to the devices. Nice puzzle, don't think so? : ) Our current candidates: Rady: The fast Lets create some views in Prony that make the data transformation from Oddy. then use DynamicData (or some RAD tool) to create/update a simple web interface for Prony (so he can even consult the transformated data from coming from Prony : ). About Tracy, she will need to be recompiled to update her DB schema (Entity framework should work) and use Reflection to explore recursively the schema and serialize data. Cons: We would have to recompile Tracy and the Prony's web interface. What do you think of the candidate(s)? What would you do?

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  • Django Threaded Commenting System

    - by Yasin Ozel
    (and sorry for my english) I am learning Python and Django. Now, my challange is developing threaded generic comment system. There is two models, Post and Comment. -Post can be commented. -Comment can be commented. (endless/threaded) -Should not be a n+1 query problem in system. (No matter how many comments, should not increase the number of queries) My current models are like this: class Post(models.Model): title = models.CharField(max_length=100) content = models.TextField() child = generic.GenericRelation( 'Comment', content_type_field='parent_content_type', object_id_field='parent_object_id' ) class Comment(models.Model): content = models.TextField() child = generic.GenericRelation( 'self', content_type_field='parent_content_type', object_id_field='parent_object_id' ) parent_content_type = models.ForeignKey(ContentType) parent_object_id = models.PositiveIntegerField() parent = generic.GenericForeignKey( "parent_content_type", "parent_object_id") Are my models right? And how can i get all comment (with hierarchy) of post, without n+1 query problem? Note: I know mttp and other modules but I want to learn this system. Edit: I run "Post.objects.all().prefetch_related("child").get(pk=1)" command and this gave me post and its child comment. But when I wanna get child command of child command a new query is running. I can change command to ...prefetch_related("child__child__child...")... then still a new query running for every depth of child-parent relationship. Is there anyone who has idea about resolve this problem?

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  • Modelling problem - Networked devices with commands

    - by Schneider
    I encountered a head scratching modelling problem today: We are modelling a physical control system composed of Devices and NetworkDevices. Any example of a Device is a TV. An example of a NetworkDevice is an IR transceiver with Ethernet connection. As you can see, to be able to control the TV over the internet we must connect the Device to the NetworkDevice. There is a one to many relationship between Device and NetworkDevice i.e. TV only has one NetworkDevice (the IR transceiver), but the IR transceiver may control many Devices (e.g. many TVs). So far no problem. The complicated bit is that every Device has a collection of Commands. The type of the Command (e.g IrCommand, SerialCommand - N.B. not currently modelled) depends on the type of NetworkDevice that the Device is connected to. In the current legacy system the Device has a collection of generic Commands (no typing) where fields are "interpreted" depending on the NetworkDevice type. How do I go about modelling this in OOP such that: You can only ever add a Command of the appropriate type, given the NetworkDevice the Device is attached to? If I change the NetworkDevice the Commands collection changes to the appropriate type Make it so the API is simple/elegant/intuitive to use

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  • Merging datasets with 2 different time variables in SAS

    - by John
    Hye Guys, for those regularly browsing this site sorry for already another question (however I did solve my last question myself!) I have another problem with merging datasets, it seems that accounting for time in datasets is a real pain in the ass. I succesfully managed to merge on months in my previous datasets, however it seems I have a final dataset which only has quarter as a time count variable. So where all my normal databases have month 1- xxx as an indicator of time, this database had quarter as an indicator of time. I still want to add the variables of this last database, let's call it TVOL, into my WORK database. Quick summary QUARTER: Quarter 0 = JAN1996-MAR1996 Month: Month 0 = JAN1996 Example: TVOL TVOL _ Ticker ____ Quarter 1500 _ AA ________ -1 52546 _ BB ________ 15 Example: WORK BETA _ Ticker ____ Month 1.52 _ AA ________ 2 1.54__ BB _______ 3 Example: Merged: BETA ______ TVOL __ Ticker ____ Month 1.52 _______ 500 ___ AA _______ 2 I now want to merge this 2 tables using following relationship if the month is in quarter 1, the data of quarter 0 has to be used, so if i have an observation i nWORK with date 2FEB1996 the TVOL of quarter -1 has to be put behind this observation. Something like IF month = quarter i use data quarter i-1. Also, as TVOL is measured quarterly and I have to put in monthly I have to take the average, so (TVOL/3) should be added as a variable. Thanks!

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  • Model login constraints based on time

    - by DaDaDom
    Good morning, for an existing web application I need to implement "time based login constraints". It means that for each user, later maybe each group, I can define timeslots when they are (not) allowed to log in into the system. As all data for the application is stored in database tables, I need to somehow create a way to model this idea in that way. My first approach, I will try to explain it here: Create a tree of login constraints (called "timeslots") with the main "categories", like "workday", "weekend", "public holiday", etc. on the top level, which are in a "sorted" order (meaning "public holiday" has a higher priority than "weekday") for each top level node create subnodes, which have a finer timespan, like "monday", "tuesday", ... below that, create an "hour" level: 0, 1, 2, ..., 23. No further details are necessary. set every member to "allowed" by default For every member of the system create a 1:n relationship member:timeslots which defines constraints, e.g. a member A may have A:monday-forbidden and A:tuesday-forbidden Do a depth-first search at every login and check if the member has a constraint. Why a depth first search? Well, I thought that it may be that a member has the rules: A:monday->forbidden, A:monday-10->allowed, A:mondey-11->allowed So a login on monday at 12:30 would fail, but one at 10:30 succeed. For performance reasons I could break the relational database paradigm and set a flag for every entry in the member-to-timeslots-table which is set to true if the member has information set for "finer" timeslots, but that's a second step. Is this model in principle a good idea? Are there existing models? Thanks.

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  • Is "Server not found" error related to Activclient?

    - by Kent
    Users are getting sporadic "Server not found" errors after idling in the browser. We have a HTTPS web application (Apache/Tomcat) using NSS for authentication on the server. The error occurs when a user opens the application and later lets it sit idle/untouched for 15 minutes. When they try to access the application they can get a "Server not found" error. Users use CAC cards with ActivClient software and our web application uses the certificates for authentication and authorization. We have been able to recreate the problem but have been unable to diagnose it. In recreating the problem the server is getting a series of "Unable to find the certificate or key necessary for authentication" errors in the NSS log associated with the browser error. These erros don't occur until the user tries to access the idle application. When the application is idle for 15 minutes the PIN is not requested yet the PIN Cache timeout in ActivClient is set at 15 minutes. All our server side timeout parameters are set to hours not minutes. IE 6 is our browser and NSS is using TLS. We have tried modifying "SetEnvIf User-Agent ".MSIE." ssl-unclean-shutdown" with no improvement. I understand that the PIN cache timeout and SSL session don't have a 1:1 relationship but the timing is suspicious. Can't find anything in the windows error logs that indicates a problem (security logs are not accessible to us). Any suggestions as to how to identify the cause of the problem would be appreciated.

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  • how to join tables sql server

    - by Rick
    Im having some trouble with joining two tables. This is what my two tables look like: Table 1 Customer_ID CustomerName Add. 1000 John Smith 1001 Mike Coles 1002 Sam Carter Table 2 Sensor_ID Location Temp CustIDFK 1000 NY 70 1002 NY 70 1000 ... ... 1001 1001 1002 Desired: Sensor_ID Location Temp CustIDFK 1000 NY 70 John Smith 1002 NY 70 Sam Carter 1000 ... ... John Smith 1001 Mike Coles 1001 1002 I have made Customer_ID from table 1 my primary key, created custIDFK in table 2 and set that as my foreign key. I am really new to sql server so I am still having trouble with the whole relationship piece of it. My goal is to match one customer_ID with one Sensor_ID. The problem is that the table 2 does not have "unique IDs" since they repeat so I cant set that to my foreign key. I know I will have to do either an inner join or outer join, I just dont know how to link the sensor id with customer one. I was thinking of giving my sensor_ID a unique ID but the data that is being inserted into table 2 is coming from another program. Any suggestions?

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  • Jekyll - How to approach asset processing (minification, spriting...)

    - by Gromix
    I recently switched to Jekyll and I find the conversion pipeline works really well. However I'm stuck on which approach to take when the process is many inputs to one output (ex: concatenating CSS files, creating image sprites...) I know several tools that can do it, that can be called either from the command line or in Ruby code directly. For ex: Jammit css sprites Compass sprites My current solution is a few Jekyll plugins that call these tools. However, it has the following problems: 1. SASS files should be processed, then concatenated/minified SASS-CSS is a Converter, and the concatenation is a Generator run on the output. Unfortunately generators are run first, which means the concatenation is always a step behind (I have to run the build twice) 2. Jekyll does not know about the source/output relationship With converters, when I run Jekyll in server mode, if I change a SASS file it automatically runs the conversion to CSS. When dealing with concatenation/spriting, I haven't found a way to do the same. I end up having to run a "normal" Jekyll build (not server auto) to update the concatenated files and sprites. Thanks for any ideas!

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