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  • Core Data Relationships in pre-populated SQLite database

    - by Cardinal
    Hi All, I'm new to Core Data. Currently I have following tables on hand: tbl_teahcer tbl_student tbl_course tbl_student_course_map ----------- ----------- ---------- ---------------------- teacher_id student_id course_id student_id name name name course_id teahcer_id And I'm going to make the xcdatamodel as below: Course Teacher ------ ------- name name teacher <<----------> courses students <<---| | Student | ------- | name |----->> courses My questions are as follows: As I'd like to create TableView for Cource Entity, is it a must to create the Inverse Relationship from Teacher to Course, and Student to Course? What is the beneit for having the Inverse Relationship? I got some pre-defined data on hand, and I'd like to create a SQLite storage for pre-populated source. How can I set up the relationships (both directions) in SQLite? Thank you for your help! Regards, Cardinal

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  • ordering an acts_as_tree relationship

    - by timpone
    I have a Category class that is defined like this: class Catergoy < ActiveRecord::Base acts_as_tree :parent_id I'd like the ordering to be by the position value which is a float such that: category-1 category-2, parent_id=1, position=0.5 category-3, parent_id=2, category-4, parent_id=1, position=1 How would I specify this? I tried acts_as_tree :parent_id :order => :position acts_as_tree :parent_id, :order => :position but these are not working. Any ideas how to specify this relationship? Or if I'm missing something else? thx in advance

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  • Entity Framework 4 CTP 5 POCO - Many-to-many configuration, insertion, and update?

    - by Saxman
    I really need someone to help me to fully understand how to do many-to-many relationship with Entity Framework 4 CTP 5, POCO. I need to understand 3 concepts: How to config my model to indicates some tables are many-to-many. How to properly do insert. How to properly do update. Here are my current models: public class MusicSheet { [Key] public int ID { get; set; } public string Title { get; set; } public string Key { get; set; } public virtual ICollection<Author> Authors { get; set; } public virtual ICollection<Tag> Tags { get; set; } } public class Author { [Key] public int ID { get; set; } public string Name { get; set; } public string Bio { get; set; } public virtual ICollection<MusicSheet> MusicSheets { get; set; } } public class Tag { [Key] public int ID { get; set; } public string TagName { get; set; } public virtual ICollection<MusicSheet> MusicSheets { get; set; } } As you can see, the MusicSheet can have many Authors or Tags, and an Author or Tag can have multiple MusicSheets. Again, my questions are: What to do on the EntityTypeConfiguration to set the relationship between them as well as mapping to an table/object that associates with the many-to-many relationship. How to insert a new music sheets (where it might have multiple authors or multiple tags). How to update a music sheet. For example, I might set TagA, TagB to MusicSheet1, but later I need to change the tags to TagA and TagC. It seems like I need to first check to see if the tags already exists, if not, insert the new tag and then associate it with the music sheet (so that I doesn't re-insert TagA?). Or this is something already handled by the framework? Thank you very much. I really hope to fully understand it rather than just doing it without fully understand what's going on. Especially on #3.

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  • Query multiple models with one value

    - by swoei
    I have multiple models which all have a FK to the same model. All I know is the FK how can I determine which of the models has the FK attached? Below an example to clearify: class ModelA(models.Model): title = models.CharField("title", max_length=80) class ModelB(models.Model): fk = models.ForeignKey(ModelA) class ModelC(models.Model): fk = models.ForeignKey(ModelA) How can I figure out without using a try/except on each model whether B or C has the FK? (The FK can only be in one of them, for the record in this case I only added two models but in the real world app there are multiple possible x amount of models which have the FK to modelA)

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  • One to two relationship in Doctrine with YAML

    - by Jeremy DeGroot
    I'm working on my first Symfony project with Doctrine, and I've run into a hitch. I'm trying to express a game with two players. The relationship I want to have is PlayerOne and PlayerTwo each being keyed to an ID in the Users table. This is part of what I've got so far: Game: actAs: { Timestampable:- } columns: id: { type: integer, notnull: true, unique: true } startDate: { type: timestamp, notnull: true } playerOne: { type: integer, notnull: true } playerTwo: { type: integer, notnull: true } winner: { type: integer, notnull:true, default:0 } relations: User: { onUpdate: cascade, local: playerOne, foreign: id} User: { onUpdate: cascade, local: playerTwo, foreign: id} That doesn't work. It builds fine, but the SQL it generates only includes a constraint for playerTwo. I've tried a few other things: User: { onUpdate: cascade, local: [playerOne, playerTwo], foreign: id} Also: User: [{ onUpdate: cascade, local: playerOne, foreign: id}, { onUpdate: cascade, local: playerTwo, foreign: id}] Those last two throw errors when I try to build. Is there anyone out there who understands what I'm trying to do and can help me achieve it?

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  • What is the relationship between IRimTable and PersistenceStore?

    - by Martin
    The BlackBerry Desktop API has the interface IRimTable which apparently maps an "application database" on a BlackBerry device to a virtual structure (i.e, IRimTable has IRimRecords, each of which has IRimField) that developer can browse the handheld device data when it is connected to a desktop computer. Meanwhile, applications in the handheld device can store its data in PersistenceStore databases. The point where I'm stuck is the PersistenceStore API doesn't define any Table or Records or Fields. Does anybody knows what is the relationship between these two classes? And how does the mapping work (if at all) ?

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  • Ruby on Rails - Create Entity with Relationship

    - by SooDesuNe
    I'm new to rails, so be nice. I'm building a "rolodex" type application, and this question is about the best way to handle creating an entity along with several relationship entities at the same time. For (a contrived) example: My application will have a Person model, which has_one Contact_Info model. On the create.html.erb page for Person it makes sense for the user of my appliction to create the person, and the contact_info at the same time. It doesn't seem right to include details for creating a contact directly in the create view/controller for person. What's the rails way to handle this?

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  • One to One relationship in MySQL

    - by Botto
    I'm trying to make a one to one relationship in a MySQL DB. I'm using the InnoDB engine and the basic table looks like this: CREATE TABLE `foo` ( `fooID` INT(11) NOT NULL PRIMARY KEY AUTO_INCREMENT, `name` TEXT NOT NULL ) CREATE TABLE `bar` ( `barName` VARCHAR(100) NOT NULL, `fooID` INT(11) NOT NULL PRIMARY KEY, CONSTRAINT `contact` FOREIGN KEY (`fooID`) REFERENCES `foo`(`fooID`) ) Now once I have set up these I alter the foo table so that the fooID also becomes a foreign key to the fooID in bar. The only issue I am facing with this is that there will be a integrity issue when I try to insert into either. I would like some help, thanks.

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  • Linq2Entities: Update relationship?

    - by Poku
    Hey, How do i create a new row in a table which have a relationship with another table? I have an Employees table and a EmployeeProjects table. One Employee can have 1-* EmployeeProjects. Now i want to create a new EmployeeProject which relates to an Employee. How do i do this? Here is want i have tried so far: var ep = new EmployeeProjects(); ep.JobNo = jobNo; employee.EmployeeProjects.Add(ep); var originalEmployee = GetEmployee(employee.Id); _entities.ApplyPropertyChanges(originalEmployee.EntityKey.EntitySetName, employee); _entities.SaveChanges();

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  • Select in a many-to-many relationship in MySQL

    - by Joff Williams
    I have two tables in a MySQL database, Locations and Tags, and a third table LocationsTagsAssoc which associates the two tables and treats them as a many-to-many relationship. Table structure is as follows: Locations --------- ID int (Primary Key) Name varchar(128) LocationsTagsAssoc ------------------ ID int (Primary Key) LocationID int (Foreign Key) TagID int (Foreign Key) Tags ---- ID int (Primary Key) Name varchar(128) So each location can be tagged with multiple tagwords, and each tagword can be tagged to multiple locations. What I want to do is select only Locations which are tagged with all of the tag names supplied. For example: I want all locations which are tagged with both "trees" and "swings". Location "Park" should be selected, but location "Forest" should not. Any insight would be appreciated. Thanks!

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  • Custom OData operation / customize EF model to hide join table in many-to-many relationship

    - by AC
    I've got a data model that has two tables with a join table for a many to many relationship & creating an OData service to expose the data for CRUD ops in a Silverlight app. What I'd like to do is abstract the join table from the service. I'm not sure if the best way to do this would be in the model (using EF in .NET3.5SP1) or if I should do it with a custom service operation. If I do it in the EF model (not sure how I'd do this), then the OOTB WCF Data Service stuff would make it easy to say [..]/Courses(1)/Modules ... otherwise I'd have to create a custom operation to do this. Is it possible to do this in the EF model and if so, how does that work?

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  • ruby on rails has_many through relationship

    - by BennyB
    Hi i'm having a little trouble with a has_many through relationship for my app and was hoping to find some help. So i've got Users & Lectures. Lectures are created by one user but then other users can then "join" the Lectures that have been created. Users have their own profile feed of the Lectures they have created & also have a feed of Lectures friends have created. This question however is not about creating a lecture but rather "Joining" a lecture that has been created already. I've created a "lecturerelationships" model & controller to handle this relationship between Lectures & the Users who have Joined (which i call "actives"). Users also then MUST "Exit" the Lecture (either by clicking "Exit" or navigating to one of the header navigation links). I'm grateful if anyone can work through some of this with me... I've got: Users.rb model Lectures.rb model Users_controller Lectures_controller then the following model lecturerelationship.rb class lecturerelationship < ActiveRecord::Base attr_accessible :active_id, :joinedlecture_id belongs_to :active, :class_name => "User" belongs_to :joinedlecture, :class_name => "Lecture" validates :active_id, :presence => true validates :joinedlecture_id, :presence => true end lecturerelationships_controller.rb class LecturerelationshipsController < ApplicationController before_filter :signed_in_user def create @lecture = Lecture.find(params[:lecturerelationship][:joinedlecture_id]) current_user.join!(@lecture) redirect_to @lecture end def destroy @lecture = Lecturerelationship.find(params[:id]).joinedlecture current_user.exit!(@user) redirect_to @user end end Lectures that have been created (by friends) show up on a users feed in the following file _activity_item.html.erb <li id="<%= activity_item.id %>"> <%= link_to gravatar_for(activity_item.user, :size => 200), activity_item.user %><br clear="all"> <%= render :partial => 'shared/join', :locals => {:activity_item => activity_item} %> <span class="title"><%= link_to activity_item.title, lecture_url(activity_item) %></span><br clear="all"> <span class="user"> Joined by <%= link_to activity_item.user.name, activity_item.user %> </span><br clear="all"> <span class="timestamp"> <%= time_ago_in_words(activity_item.created_at) %> ago. </span> <% if current_user?(activity_item.user) %> <%= link_to "delete", activity_item, :method => :delete, :confirm => "Are you sure?", :title => activity_item.content %> <% end %> </li> Then you see I link to the the 'shared/join' partial above which can be seen in the file below _join.html.erb <%= form_for(current_user.lecturerelationships.build(:joinedlecture_id => activity_item.id)) do |f| %> <div> <%= f.hidden_field :joinedlecture_id %> </div> <%= f.submit "Join", :class => "btn btn-large btn-info" %> <% end %> Some more files that might be needed: config/routes.rb SampleApp::Application.routes.draw do resources :users do member do get :following, :followers, :joined_lectures end end resources :sessions, :only => [:new, :create, :destroy] resources :lectures, :only => [:create, :destroy, :show] resources :relationships, :only => [:create, :destroy] #for users following each other resources :lecturerelationships, :only => [:create, :destroy] #users joining existing lectures So what happens is the lecture comes in my activity_feed with a Join button option at the bottom...which should create a lecturerelationship of an "active" & "joinedlecture" (which obviously are supposed to be coming from the user & lecture classes. But the error i get when i click the join button is as follows: ActiveRecord::StatementInvalid in LecturerelationshipsController#create SQLite3::ConstraintException: constraint failed: INSERT INTO "lecturerelationships" ("active_id", "created_at", "joinedlecture_id", "updated_at") VALUES (?, ?, ?, ?) Also i've included my user model (seems the error is referring to it) user.rb class User < ActiveRecord::Base attr_accessible :email, :name, :password, :password_confirmation has_secure_password has_many :lectures, :dependent => :destroy has_many :lecturerelationships, :foreign_key => "active_id", :dependent => :destroy has_many :joined_lectures, :through => :lecturerelationships, :source => :joinedlecture before_save { |user| user.email = email.downcase } before_save :create_remember_token validates :name, :presence => true, :length => { :maximum => 50 } VALID_EMAIL_REGEX = /\A[\w+\-.]+@[a-z\d\-.]+\.[a-z]+\z/i validates :email, :presence => true, :format => { :with => VALID_EMAIL_REGEX }, :uniqueness => { :case_sensitive => false } validates :password, :presence => true, :length => { :minimum => 6 } validates :password_confirmation, :presence => true def activity # This feed is for "My Activity" - basically lectures i've started Lecture.where("user_id = ?", id) end def friendactivity Lecture.from_users_followed_by(self) end # lECTURE TO USER (JOINING) RELATIONSHIPS def joined?(selected_lecture) lecturerelationships.find_by_joinedlecture_id(selected_lecture.id) end def join!(selected_lecture) lecturerelationships.create!(:joinedlecture_id => selected_lecture.id) end def exit!(selected_lecture) lecturerelationships.find_by_joinedlecture_id(selected_lecture.id).destroy end end Thanks for any and all help - i'll be on here for a while so as mentioned i'd GREATLY appreciate someone who may have the time to work through my issues with me...

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  • How do I specify a null relation in SQLAlchemy?

    - by Jesse
    Not sure what the correct title for this question should be. I have the following schema: Matters have a one-many relationship to WorkItems. WorkItems have a one-one (or one-zero) relationship to LineItems. I am trying to create the following relation between Matters and WorkItems Matter.unbilled_work_items = orm.relation(WorkItem, primaryjoin = (Matter.id == WorkItem.matter_id) and (WorkItem.line_item_id == None), foreign_keys = [WorkItem.matter_id, WorkItem.line_item_id], viewonly=True ) This throws: AttributeError: '_Null' object has no attribute 'table' That seems to be saying that the second clause in the primaryjoin returns an object of type _Null, but it seems to be expecting something with a "table" attribute. This seems like it should be pretty straightforward to me, am I missing something obvious?

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  • Representing parent-child relationships in SharePoint lists

    - by Chris Farmer
    I need to create some functionality in our SharePoint app that populates a list or lists with some simple hierarchical data. Each parent record will represent a "submission" and each child record will be a "submission item." There's a 1-to-n relationship between submissions and submission items. Is this practical to do in SharePoint? The only types of list relationships I've done so far are lookup columns, but this seems a bit different. Also, once such a list relationship is established, then what's the best way to create views on this kind of data. I'm almost convinced that it'd be easier just to write this stuff to an external database, but I'd like to give SharePoint a shot in order to take advantage of the automated search capabilities.

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  • Selecting one object from a one-to-many relationship in Hibernate

    - by Nick Thomson
    I have two tables: Job job_id, <other data> Job_Link job_link_id, job_id, start_timestamp, end_timestamp, <other data> There may be multiple records in Job_Link specifying the same job_id with the start_timestamp and end_timestamps to indicate when those records are considered "current", it is guaranteed that start_timestamp and end_timestamp will not overlap. We have entities for both the Job and Job_Link tables and defining a one-to-many relationship to load all the job_links wouldn't be a problem. However we'd like to avoid that and have a single job_link item in the Job entity that will contain only the "current" Job_Link object. Is there any way to achive that?

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  • Cakephp: Designpattern for creation of models in hasMany relationship

    - by Chris
    I have two Models: Car and Passenger. Car hasMany Passenger Passenger belongsTo Car I managed to create add functionailty for each model and managed to resolve the hasMany relationship between them. Now I'm trying to create a addCar function and view that allows the user to create a new car and automatically generate Passengers. I thought of something like this The view asks the user enter the car information The view has some field that allows to temporarly add new passengers and remove remove them When the user saves the new car, the entities for the passengers are created, the entity for the car is created and the passengers are linked to the car. If the user decides to cacnel everything, the DB remains unchanged. Now my question is: What is the best way to do this? Is there a pattern / tutorial to follow for such a entity and associated subentity creation? To clarify: The passengers associated with each car do not exist prior to the existence of the car.

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  • Table per subclass inheritance relationship: How to query against the Parent class without loading a

    - by Arthur Ronald F D Garcia
    Suppose a Table per subclass inheritance relationship which can be described bellow (From wikibooks.org - see here) Notice Parent class is not abstract @Entity @Inheritance(strategy=InheritanceType.JOINED) public class Project { @Id private long id; // Other properties } @Entity @Table(name="LARGEPROJECT") public class LargeProject extends Project { private BigDecimal budget; } @Entity @Table(name="SMALLPROJECT") public class SmallProject extends Project { } I have a scenario where i just need to retrieve the Parent class. Because of performance issues, What should i do to run a HQL query in order to retrieve the Parent class and just the Parent class without loading any subclass ???

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  • Many-to-one relationship in SQLAlchemy

    - by Arrieta
    This is a beginner-level question. I have a catalog of mtypes: mtype_id name 1 'mtype1' 2 'mtype2' [etc] and a catalog of Objects, which must have an associated mtype: obj_id mtype_id name 1 1 'obj1' 2 1 'obj2' 3 2 'obj3' [etc] I am trying to do this in SQLAlchemy by creating the following schemas: mtypes_table = Table('mtypes', metadata, Column('mtype_id', Integer, primary_key=True), Column('name', String(50), nullable=False, unique=True), ) objs_table = Table('objects', metadata, Column('obj_id', Integer, primary_key=True), Column('mtype_id', None, ForeignKey('mtypes.mtype_id')), Column('name', String(50), nullable=False, unique=True), ) mapper(MType, mtypes_table) mapper(MyObject, objs_table, properties={'mtype':Relationship(MType, backref='objs', cascade="all, delete-orphan")} ) When I try to add a simple element like: mtype1 = MType('mtype1') obj1 = MyObject('obj1') obj1.mtype=mtype1 session.add(obj1) I get the error: AttributeError: 'NoneType' object has no attribute 'cascade_iterator' Any ideas?

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  • Making a many-to-many relationship using DataRelations object

    - by dotnetdev
    Hi, I have about 200 tables which need to relate to another table in a many-to-many fashion. I have the tables (including the intersection table) ready IN SQL Server. How can I write code using the data relation object to make the relationship? The tables are: PartStatPartName PartsMaterialsIntersection << Materials The materials table needs to have a foreign key from the PartStatPartName table. I tried various approaches using the DataRelation class but the change did not sync to SQL Server, despite being connected and adding the relation, and then calling AcceptChanges() on the dataset. Any guidance much appreciated. I have seen some threads covering the same problem but need an example in code so I can follow the right method. Thanks

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  • One-to-many relationship related to many tables

    - by Andrey
    I have a scenario where: there are two (or more) tables that represent independent items. lets say Users and Companies Both of these tables need addresses stored. Each one can have one or more address In a normal 1 to many scenario Addresses table woudl just have a UserId or a CompanyId creating a normal 1 to many relationship. In this case i have a few approaches i can think of the Addresses table could have both a UserId and a CompanyId and only one would be used for each record. 2 keys could be used ObjectId and ObjectType So Object id would have a UserId or a CompanyId, and ObjectType woudl be User or Company Create an ObjectTable and add ObjectId to Users and Companies. Addresses would then have an OjbectId I do not really like any of these solutions. i am wondering what is the best approach here. On another note i will most likely user linqtosql for my data access layer.

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  • How can I traverse a reverse generic relation in a Django template?

    - by user569139
    I have the following class that I am using to bookmark items: class BookmarkedItem(models.Model): is_bookmarked = models.BooleanField(default=False) user = models.ForeignKey(User) content_type = models.ForeignKey(ContentType) object_id = models.PositiveIntegerField() content_object = generic.GenericForeignKey() And I am defining a reverse generic relationship as follows: class Link(models.Model): url = models.URLField() bookmarks = generic.GenericRelation(BookmarkedItem) In one of my views I generate a queryset of all links and add this to a context: links = Link.objects.all() context = { 'links': links } return render_to_response('links.html', context) The problem I am having is how to traverse the generic relationship in my template. For each link I want to be able to check the is_bookmarked attribute and change the add/remove bookmark button according to whether the user already has it bookmarked or not. Is this possible to do in the template? Or do I have to do some additional filtering in the view and pass another queryset?

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  • Many-to-many relationship in oop

    - by Manu
    what is best way to model many-to-many relationship? lets say we have a two classes , Team and Player any given Player can be in multiple Team s any Team can have as many Player s as they like I like to call methods like playerX.getTeamList() to get the list of all the Team s he/she is in teamY.getPlayerList() to get the list of all the Player s in the team (or have some other way to do this effectively) I can think of two ways of doing this , but they just don't feels like good oop pattens. can you think of any good ways , perhaps a design patten ?

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  • Drupal Views: Render Null Result for Relationship as 0

    - by Kyle S
    I have a View configured in Drupal to return nodes, sorting them by their average vote in descending order. For the purpose of the View, the value of the average votes is a Relationship. I noticed that nodes with no votes are displayed after nodes with a negative average. Nodes with no votes should have an average of 0, but I believe the MySQL JOIN is causing NULL values to be returned (as there are no matching rows in the joined table, since a row is created after the first vote is cast for that item). I discovered that with MySQL it is possible to output all values that are NULL in a column as another value with IFNULL(column_name,'other value'). I feel like I would need to modify the Views module in order to obtain this functionality, but I'm hoping that there is some sort of option that returns NULL values in a relation (a relation doesn't exist for the item) as 0 instead of NULL, so that I can properly sort the nodes. The modules I am using include Views, Voting API, Vote Up/Down, and CTools. Thanks.

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  • Using iPhone Core Data to many Relationship

    - by BLeB
    When I define a to many relationship between entities in Xcode and then generate the data class from the entity I get a header with the following methods defined: @interface PriceList (CoreDataGeneratedAccessors) - (void)addItemsObject:(PriceListItem *)value; - (void)removeItemsObject:(PriceListItem *)value; - (void)addItems:(NSSet *)value; - (void)removeItems:(NSSet *)value; @end When I attempt to call addItemsObject with the following code a doesNotRecognizeSelector exception is thrown. PriceListItem *item = [NSEntityDescription insertNewObjectForEntityForName:@"PriceListItem" inManagedObjectContext:managedObjectContext]; item.cat = [attributeDict valueForKey:@"c"]; item.sel = [attributeDict valueForKey:@"s"]; [self addItemsObject:item]; From what I have read I do not have to implement these methods and that they are generated at runtime. Any ideas?

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