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• Updating join fields in an ORM command

  - by Jono

  I have a question about object relational updates on join fields. I am working on a project using codeigniter with datamapper dmz. But I think my problem is with general understanding of ORMs. So fell free to answer with any ORM you know. I have two tables, Goods and Tags. One good can have many tags. Everything is working, but I am looking for a way to merge tags. Meaning I decide I want to remove tag A and instead have everything that is tagged by it, now be tagged by tag B. I only have models for the goods and the tags. There is no separate model for the join relationship, as I believe these ORMs were designed to work. I know how to delete a tag. But I dont know how to reach into the join table to redirect the references since there is no model for the join table. I would rather use the ORM then issuing a raw SQL command.

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• Why do pure virtual base classes get direct access to static data members while derived instances do

  - by Shamster

  I've created a simple pair of classes. One is pure virtual with a static data member, and the other is derived from the base, as follows: #include <iostream> template <class T> class Base { public: Base (const T _member) { member = _member; } static T member; virtual void Print () const = 0; }; template <class T> T Base<T>::member; template <class T> void Base<T>::Print () const { std::cout << "Base: " << member << std::endl; } template <class T> class Derived : public Base<T> { public: Derived (const T _member) : Base<T>(_member) { } virtual void Print () const { std::cout << "Derived: " << this->member << std::endl; } }; I've found from this relationship that when I need access to the static data member in the base class, I can call it with direct access as if it were a regular, non-static class member. i.e. - the Base::Print() method does not require a this- modifier. However, the derived class does require the this-member indirect access syntax. I don't understand why this is. Both class methods are accessing the same static data, so why does the derived class need further specification? A simple call to test it is: int main () { Derived<double> dd (7.0); dd.Print(); return 0; } which prints the expected "Derived: 7"

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• SCD2 + Merge Statement + SQL Server

  - by Nev_Rahd

  I am trying work out with MERGE statment to Insert / Update Dimension Table of Type SCD2 My source is a Table var to Merge with Dimension table. My MERGE statement is throwing an error as: The target table 'DM.DATA_ERROR.ERROR_DIMENSION' of the INSERT statement cannot be on either side of a (primary key, foreign key) relationship when the FROM clause contains a nested INSERT, UPDATE, DELETE, or MERGE statement. Found reference constraint 'FK_ERROR_DIMENSION_to_AUDIT_CreatedBy'. My MERGE Statement: DECLARE @DATAERROROBJECT AS [ERROR_DIMENSION] INSERT INTO DM.DATA_ERROR.ERROR_DIMENSION SELECT ERROR_CODE, DATA_STREAM_ID, [ERROR_SEVERITY], DATA_QUALITY_RATING, ERROR_LONG_DESCRIPTION, ERROR_DESCRIPTION, VALIDATION_RULE, ERROR_TYPE, ERROR_CLASS, VALID_FROM, VALID_TO, CURR_FLAG, CREATED_BY_AUDIT_SK, UPDATED_BY_AUDIT_SK FROM (MERGE DM.DATA_ERROR.ERROR_DIMENSION ED USING @DATAERROROBJECT OBJ ON(ED.ERROR_CODE = OBJ.ERROR_CODE AND ED.DATA_STREAM_ID = OBJ.DATA_STREAM_ID) WHEN NOT MATCHED THEN INSERT VALUES( OBJ.ERROR_CODE ,OBJ.DATA_STREAM_ID ,OBJ.[ERROR_SEVERITY] ,OBJ.DATA_QUALITY_RATING ,OBJ.ERROR_LONG_DESCRIPTION ,OBJ.ERROR_DESCRIPTION ,OBJ.VALIDATION_RULE ,OBJ.ERROR_TYPE ,OBJ.ERROR_CLASS ,GETDATE() ,'9999-12-13' ,'Y' ,1 ,1 ) WHEN MATCHED AND ED.CURR_FLAG = 'Y' AND ( ED.[ERROR_SEVERITY] <> OBJ.[ERROR_SEVERITY] OR ED.[DATA_QUALITY_RATING] <> OBJ.[DATA_QUALITY_RATING] OR ED.[ERROR_LONG_DESCRIPTION] <> OBJ.[ERROR_LONG_DESCRIPTION] OR ED.[ERROR_DESCRIPTION] <> OBJ.[ERROR_DESCRIPTION] OR ED.[VALIDATION_RULE] <> OBJ.[VALIDATION_RULE] OR ED.[ERROR_TYPE] <> OBJ.[ERROR_TYPE] OR ED.[ERROR_CLASS] <> OBJ.[ERROR_CLASS] ) THEN UPDATE SET ED.CURR_FLAG = 'N', ED.VALID_TO = GETDATE() OUTPUT $ACTION ACTION_OUT, OBJ.ERROR_CODE ERROR_CODE, OBJ.DATA_STREAM_ID DATA_STREAM_ID, OBJ.[ERROR_SEVERITY] [ERROR_SEVERITY], OBJ.DATA_QUALITY_RATING DATA_QUALITY_RATING, OBJ.ERROR_LONG_DESCRIPTION ERROR_LONG_DESCRIPTION, OBJ.ERROR_DESCRIPTION ERROR_DESCRIPTION, OBJ.VALIDATION_RULE VALIDATION_RULE, OBJ.ERROR_TYPE ERROR_TYPE, OBJ.ERROR_CLASS ERROR_CLASS, GETDATE() VALID_FROM, '9999-12-31' VALID_TO, 'Y' CURR_FLAG, 555 CREATED_BY_AUDIT_SK, 555 UPDATED_BY_AUDIT_SK ) AS MERGE_OUT WHERE MERGE_OUT.ACTION_OUT = 'UPDATE'; What am I doing wrong ?

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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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• Is the RESTORE process dependent on schema?

  - by Martin Aatmaa

  Let's say I have two database instances: InstanceA - Production server InstanceB - Test server My workflow is to deploy new schema changes to InstanceB first, test them, and then deploy them to InstanceA. So, at any one time, the instance schema relationship looks like this: InstanceA - Schema Version 1.5 InstanceB - Schema Version 1.6 (new version being tested) An additional part of my workflow is to keep the data in InstanceB as fresh as possible. To fulfill this, I am taking the database backups of InstanceA and applying them (restoring them) to InstanceB. My question is, how does schema version affect the restoral process? I know I can do this: Backup InstanceA - Schema Version 1.5 Restore to InstanceB - Schema Version 1.5 But can I do this? Backup InstanceA - Schema Version 1.5 Restore to InstanceB - Schema Version 1.6 (new version being tested) If no, what would the failure look like? If yes, would the type of schema change matter? For example, if Schema Version 1.6 differed from Schema Version 1.5 by just having an altered storec proc, I imagine that this type of schema change should't affect the restoral process. On the other hand, if Schema Version 1.6 differed from Schema Version 1.5 by having a different table definition (say, an additional column), I image this would affect the restoral process. I hope I've made this clear enough. Thanks in advance for any input!

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• When are SQL views appropriate in ASP.net MVC?

  - by sslepian

  I've got a table called Protocol, a table called Eligibility, and a Protocol_Eligibilty table that maps the two together (a many to many relationship). If I wanted to make a perfect copy of an entry in the Protocol table, and create all the needed mappings in the Protocol_Eligibility table, would using an SQL view be helpful, from a performance standpoint? Protocol will have around 1000 rows, Eligibility will have about 200, and I expect each Protocol to map to about 10 Eligibility rows and each Eligibility to map to over 100 rows in Protocol. Here's how I'm doing this with the view: var pel_original = (from pel in _documentDataModel.Protocol_Eligibility_View where pel.pid == id select pel); Protocol_Eligibility newEligibility; foreach (var pel_item in pel_original) { newEligibility = new Protocol_Eligibility(); newEligibility.Eligibility = (from pel in _documentDataModel.Eligibility where pel.ID == pel_item.eid select pel).First(); newEligibility.Protocol = newProtocol; newEligibility.ordering = pel_item.ordering; _documentDataModel.AddToProtocol_Eligibility(newEligibility); } And this is without the view: var pel_original = (from pel in _documentDataModel.Protocol_Eligibility where pel.Protocol.ID == id select pel); Protocol_Eligibility newEligibility; foreach (var pel_item in pel_original) { pel_item.EligibilityReference.Load(); newEligibility = new Protocol_Eligibility(); newEligibility.Eligibility = pel_item.Eligibility; newEligibility.Protocol = newProtocol; newEligibility.ordering = pel_item.ordering; _documentDataModel.AddToProtocol_Eligibility(newEligibility); }

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• What do you need to implement to provide a Content Set for an NSArrayController?

  - by whuuh

  Heys, I am writing something in Xcode. I use Core Data for persistency and link the view and the model together with Cocoa Bindings; pretty much your ordinary Core Data application. I have an array controller (NSArrayController) in my Xib. This has its managedObjectContext bound to the AppDelegate, as is convention, and tracks an entity. So far so good. Now, the "Content Set" biding of this NSArrayController limits its content set (as you'd expect), by a keyPath from the selection in another NSArrayController (otherAc.selection.detailsOfMaster). This is the usual way to implement a Master-Detail relationship. I want to variably change the key path at runtime, using other controls. This way, I sould return a content set that includes several other content sets, which is all advanced and beyond Interface Builder. To achieve this, I think I should bind the Content Set to my AppDelegate instead. I have tried to do this, but don't know what methods to implement. If I just create the KVC methods (objectSet, setObjectSet), then I can provide a Content Set for the Array Controller in the contentSet method. However, I don't think I'm binding this properly, because it doesn't "refresh". I'm new to binding; what do I need to implement to properly update the Content Set when other things, like the selection in the master NSArrayController, changes?

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• Creating self-referential tables with polymorphism in SQLALchemy

  - by Jace

  I'm trying to create a db structure in which I have many types of content entities, of which one, a Comment, can be attached to any other. Consider the following: from datetime import datetime from sqlalchemy import create_engine from sqlalchemy import Column, ForeignKey from sqlalchemy import Unicode, Integer, DateTime from sqlalchemy.orm import relation, backref from sqlalchemy.ext.declarative import declarative_base Base = declarative_base() class Entity(Base): __tablename__ = 'entities' id = Column(Integer, primary_key=True) created_at = Column(DateTime, default=datetime.utcnow, nullable=False) edited_at = Column(DateTime, default=datetime.utcnow, onupdate=datetime.utcnow, nullable=False) type = Column(Unicode(20), nullable=False) __mapper_args__ = {'polymorphic_on': type} # <...insert some models based on Entity...> class Comment(Entity): __tablename__ = 'comments' __mapper_args__ = {'polymorphic_identity': u'comment'} id = Column(None, ForeignKey('entities.id'), primary_key=True) _idref = relation(Entity, foreign_keys=id, primaryjoin=id == Entity.id) attached_to_id = Column(Integer, ForeignKey('entities.id'), nullable=False) #attached_to = relation(Entity, remote_side=[Entity.id]) attached_to = relation(Entity, foreign_keys=attached_to_id, primaryjoin=attached_to_id == Entity.id, backref=backref('comments', cascade="all, delete-orphan")) text = Column(Unicode(255), nullable=False) engine = create_engine('sqlite://', echo=True) Base.metadata.bind = engine Base.metadata.create_all(engine) This seems about right, except SQLAlchemy doesn't like having two foreign keys pointing to the same parent. It says ArgumentError: Can't determine join between 'entities' and 'comments'; tables have more than one foreign key constraint relationship between them. Please specify the 'onclause' of this join explicitly. How do I specify onclause?

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• How do I left join tables in unidirectional many-to-one in Hibernate?

  - by jbarz

  I'm piggy-backing off of http://stackoverflow.com/questions/2368195/how-to-join-tables-in-unidirectional-many-to-one-condition. If you have two classes: class A { @Id public Long id; } class B { @Id public Long id; @ManyToOne @JoinColumn(name = "parent_id", referencedColumnName = "id") public A parent; } B - A is a many to one relationship. I understand that I could add a Collection of Bs to A however I do not want that association. So my actual question is, Is there an HQL or Criteria way of creating the SQL query: select * from A left join B on (b.parent_id = a.id) This will retrieve all A records with a Cartesian product of each B record that references A and will include A records that have no B referencing them. If you use: from A a, B b where b.a = a then it is an inner join and you do not receive the A records that do not have a B referencing them. I have not found a good way of doing this without two queries so anything less than that would be great. Thanks.

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• Asp.Net Login Control very slow initial connection to Non-Trusted AD Domain

  - by Eric Brown - Cal

  ASP.NET Login control is very slow making the initial connection to AD when authenticating to a different domain than the domain the web server is a member of. Problem occurs for the IIS server and when using with the Visual Studio's built in web server. It takes about 30 seconds the first time when attempting to use the control to connect against another domain. There is no trust relationship bewteen the web server's domain and the other domains (attempted connecting to several different domains). Subsequent connections execute quickly until the connection times out. Using Systernals Process Monitor to troubleshoot, there are two OpenQuery operations right before the delay to "C:\WINDOWS\asembly\GAC_MSIL\System.DirectoryServices\2.0.0.0_b03f5f7f11d50a3a\Netapi32.dll with a result NAME NOT FOUND" and right after the 30 second delay the TCP Send and TCP Recieves indicate communication begins with the AD server. Things we have tried: Impersonating an administrator on the web server in the web.config; Granting permissions to the CryptoKeys to the NetworkService and ASPNET; Specifying by IP instead of DNS name; Multiple variations of specifying the name and ldap server with domains and OU's; Local host entries; Looked for ports being blocked (SYN_SENT) with netstat -an. Nslookup resolves all the domains and systems involved correectly. TraceRt shows the Correct routes Any Idea or hints are greately appreicated.

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• Wpf binding with nested properties

  - by byte

  ViewModel I have a property of type Member called KeyMember. The 'Member' type has an ObservableCollection called Addresses. The Address is composed of two strings - street and postcode . View I have a ListBox whose item source need to be set to ViewModels's KeyMember property and it should display the Street of all the Past Addresses in the collection. Question My ViewModel and View relationship is established properly. I am able to write a data template for the above simple case as below <ListBox ItemsSource="{Binding KeyMember.Addresses}"> <ListBox.ItemTemplate> <DataTemplate DataType="Address"> <TextBlock Text="{Binding Street}"/> </DataTemplate> </ListBox.ItemTemplate> </ListBox> How would I write the DataTemplate if I change KeyMember from type Member to ObservableCollection< Member assuming that the collection has only one element. PS: I know that for multiple elements in collection, I will have to implement the Master-Detail pattern/scenario.

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• entity framework - getting null exception using foreign key

  - by Nick

  Having some trouble with what should be a very simple scenario. For example purposes, I have two tables: -Users -Comments There is a one-to-many relationship set up for this; there is a foreign key from Comments.CommentorID to Users.UserID. When I do the LINQ query and try to bind to a DataList, I get a null exception. Here is the code: FKMModel.FKMEntities ctx = new FKMModel.FKMEntities(); IQueryable<Comment> CommentQuery = from x in ctx.Comment where x.SiteID == 101 select x; List<Comment> Comments = CommentQuery.ToList(); dl_MajorComments.DataSource = Comments; dl_MajorComments.DataBind(); In the ASPX page, I have the following as an ItemTemplate (I simplified it and took out the styling, etc, for purposes of posting here since it's irrelevant): <div> <%# ((FKMModel.Comment)Container.DataItem).FKMUser.Username %> <%# ((FKMModel.Comment)Container.DataItem).CommentDate.Value.ToShortDateString() %> <%# ((FKMModel.Comment)Container.DataItem).CommentTime %> </div> The exception occurs on the first binding (FKMUser.Username). Since the foreign key is set up, I should have no problem accessing any properties from the Users table. Intellisense set up the FKMUser navigation property and it knows the properties of that foreign table. What is going on here??? Thanks, Nick

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• Cakephp how to use Set Class to make an assoc array?

  - by michael

  I have the output array from a $Model-find() query which also pulls data from a hasMany relationship: Array( [Parent] => Array ( [id] => 1 ) [Child] => Array ( [0] => Array ( [id] => aaa [score] => 3 [src] => stage6/tn~4bbb38cc-0018-49bf-96a9-11a0f67883f5.jpg [parent_id] => 1 ) [1] => Array ( [id] => bbb [score] => 5 [src] => stage0/tn~4bbb38cc-00ac-4b25-b074-11a0f67883f5.jpg [parent_id] => 1 ) [2] => Array ( [id] => ccc [score] => 2 [src] => stage4/tn~4bbb38cc-01c8-44bd-b71d-11a0f67883f5.jpg [parent_id] => 1 ) ) ) I'd like to transform this output into something like this, where the child id is the key to additional child attributes: Array( [aaa] => Array ( [score] => 3 [src] => stage6/tn~4bbb38cc-0018-49bf-96a9-11a0f67883f5.jpg ) [bbb] => Array ( [score] => 5 [src] => stage0/tn~4bbb38cc-00ac-4b25-b074-11a0f67883f5.jpg ) [ccc] => Array ( [score] => 2 [src] => stage4/tn~4bbb38cc-01c8-44bd-b71d-11a0f67883f5.jpg ) } Is there an easy way to use Set::extract, Set::combine, Set::insert, etc. to do this efficiently? I cannot figure it out.

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• Can can I reference extended methods/params without having to cast from the base class object return

  - by Greg

  Hi, Is there away to not have a "cast" the top.First().Value() return to "Node", but rather have it automatically assume this (as opposed to NodeBase), so I then see extended attributes for the class I define in Node? That is is there a way to say: top.Nodes.First().Value.Path; as opposed to now having to go: ((Node)top.Nodes.First().Value).Path) thanks [TestMethod()] public void CreateNoteTest() { var top = new Topology(); Node node = top.CreateNode("a"); node.Path = "testpath"; Assert.AreEqual("testpath", ((Node)top.Nodes.First().Value).Path); // *** HERE *** } class Topology : TopologyBase<string, Node, Relationship> { } class Node : NodeBase<string> { public string Path { get; set; } } public class NodeBase<T> { public T Key { get; set; } public NodeBase() { } public NodeBase(T key) { Key = key; } } public class TopologyBase<TKey, TNode, TRelationship> where TNode : NodeBase<TKey>, new() where TRelationship : RelationshipBase<TKey>, new() { // Properties public Dictionary<TKey, NodeBase<TKey>> Nodes { get; private set; } public List<RelationshipBase<TKey>> Relationships { get; private set; } }

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• Combining multiple rows into one row, Oracle

  - by Torbjørn

  Hi. I'm working with a database which is created in Oracle and used in a GIS-software through SDE. One of my colleuges is going to make some statistics out of this database and I'm not capable of finding a reasonable SQL-query for getting the data. I have two tables, one with registrations and one with registrationdetails. It's a one to many relationship, so the registration can have one or more details connected to it (no maximum number). table: Registration RegistrationID Date TotLenght 1 01.01.2010 5 2 01.02.2010 15 3 05.02.2009 10 2.table: RegistrationDetail DetailID RegistrationID Owner Type Distance 1 1 TD UB 1,5 2 1 AB US 2 3 1 TD UQ 4 4 2 AB UQ 13 5 2 AB UR 13,1 6 3 TD US 5 I want the resulting selection to be something like this: RegistrationID Date TotLenght DetailID RegistrationID Owner Type Distance DetailID RegistrationID Owner Type Distance DetailID RegistrationID Owner Type Distance 1 01.01.2010 5 1 1 TD UB 1,5 2 1 AB US 2 3 1 TD UQ 4 2 01.02.2010 15 4 2 AB UQ 13 5 2 AB UR 13,1 3 05.02.2009 10 6 3 TD US 5 With a normal join I get one row per each registration and detail. Can anyone help me with this? I don't have administrator-rights for the database, so I can't create any tables or variables. If it's possible, I could copy the tables into Access.

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• Why doesn't is operator take in consideration if the explicit operator is overriden when checking ty

  - by Galilyou

  Hey Guys, Consider this code sample: public class Human { public string Value { get; set;} } public class Car { public static explicit operator Human (Car c) { Human h = new Human(); h.Value = "Value from Car"; return h; } } public class Program { public static void Mani() { Car c = new Car(); Human h = (Human)c; Console.WriteLine("h.Value = {0}", h.Value); Console.WriteLine(c is Human); } } Up I provide a possibility of an explicit cast from Car to Human, though Car and Human hierarchically are not related! The above code simply means that "Car is convertible to human" However, if you run the snippet you will find the expression c is Human evaluates to false! I used to believe that the is operator is kinda expensive cause it attempts to do an actual cast that might result in an InvalidCastException. If the operator is trying to cast, then the cast should succeed as there's an operator logic that should perform the cast! What does "is" test? Does test a hierarchical "is-a" relationship? Does test whether a variable type is convertible to a type?

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• Need a SQL statement focus on combination of tables but entries always with uinque ID

  - by Registered User KC

  Hi All, I need SQL code to solve the tables combination problem, described on below: Table old data: name version status lastupdate ID A 0.1 on 6/8/2010 1 B 0.1 on 6/8/2010 2 C 0.1 on 6/8/2010 3 D 0.1 on 6/8/2010 4 E 0.1 on 6/8/2010 5 F 0.1 on 6/8/2010 6 G 0.1 on 6/8/2010 7 Table new data: name version status lastupdate ID A 0.1 on 6/18/2010 #B entry deleted C 0.3 on 6/18/2010 #version_updated C1 0.1 on 6/18/2010 D 0.1 on 6/18/2010 E 0.1 off 6/18/2010 #status_updated F 0.1 on 6/18/2010 G 0.1 on 6/18/2010 H 0.1 on 6/18/2010 #new_added H1 0.1 on 6/18/2010 #new_added the difference of new data and old date: B entry deleted C entry version updated E entry status updated C1/H/H1 entry new added What I want is always keeping the ID - name mapping relationship in old data table no matter how data changed later, a.k.a the name always has a unique ID number bind with it. If entry has update, then update the data, if entry is new added, insert to the table then give a new assigned unique ID. However, I can only use SQL with simple select or update statement then it may too hard for me to write such code, then I hope someone with expertise can give direction, no details needed on the different of SQL variant, a standard sql code as sample is enough. Thanks in advance! Rgs KC

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• What are the options for overriding Django's cascading delete behaviour?

  - by Tom

  Django models generally handle the ON DELETE CASCADE behaviour quite adequately (in a way that works on databases that don't support it natively.) However, I'm struggling to discover what is the best way to override this behaviour where it is not appropriate, in the following scenarios for example: ON DELETE RESTRICT (i.e. prevent deleting an object if it has child records) ON DELETE SET NULL (i.e. don't delete a child record, but set it's parent key to NULL instead to break the relationship) Update other related data when a record is deleted (e.g. deleting an uploaded image file) The following are the potential ways to achieve these that I am aware of: Override the model's delete() method. While this sort of works, it is sidestepped when the records are deleted via a QuerySet. Also, every model's delete() must be overridden to make sure Django's code is never called and super() can't be called as it may use a QuerySet to delete child objects. Use signals. This seems to be ideal as they are called when directly deleting the model or deleting via a QuerySet. However, there is no possibility to prevent a child object from being deleted so it is not usable to implement ON CASCADE RESTRICT or SET NULL. Use a database engine that handles this properly (what does Django do in this case?) Wait until Django supports it (and live with bugs until then...) It seems like the first option is the only viable one, but it's ugly, throws the baby out with the bath water, and risks missing something when a new model/relation is added. Am I missing something? Any recommendations?

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• Objective-C Getter Memory Management

  - by Marian André

  I'm fairly new to Objective-C and am not sure how to correctly deal with memory management in the following scenario: I have a Core Data Entity with a to-many relationship for the key "children". In order to access the children as an array, sorted by the column "position", I wrote the model class this way: @interface AbstractItem : NSManagedObject { NSArray * arrangedChildren; } @property (nonatomic, retain) NSSet * children; @property (nonatomic, retain) NSNumber * position; @property (nonatomic, retain) NSArray * arrangedChildren; @end @implementation AbstractItem @dynamic children; @dynamic position; @synthesize arrangedChildren; - (NSArray*)arrangedChildren { NSArray* unarrangedChildren = [[self.children allObjects] retain]; NSSortDescriptor* sortDescriptor = [[NSSortDescriptor alloc] initWithKey:@"position" ascending:YES]; [arrangedChildren release]; arrangedChildren = [unarrangedChildren sortedArrayUsingDescriptors:[NSArray arrayWithObject:sortDescriptor]]; [sortDescriptor release]; [unarrangedChildren release]; return [arrangedChildren retain]; } @end I'm not sure whether or not to retain unarrangedChildren and the returned arrangedChildren (first and last line of the arrangedChildren getter). Does the NSSet allObjects method already return a retained array? It's probably too late and I have a coffee overdose. I'd be really thankful if someone could point me in the right direction. I guess I'm missing vital parts of memory management knowledge and I will definitely look into it thoroughly.

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• Displaying tree path of record in SQL Server 2005

  - by jskiles1

  An example of my tree table is: ([id] is an identity) [id], [parent_id], [path] 1, NULL, 1 2, 1, 1-2 3, 1, 1-3 4, 3, 1-3-4 My goal is to query quickly for multiple rows of this table and view the full path of the node from its root, through its superiors, down to itself. The ultimate question is, should I generate this path on inserts and maintain it in its own column or generate this path on query to save disk space? I guess it depends if this table is write heavy or read heavy. I've been contemplating several approaches to using the "path" characteristic of this parent/child relationship and I just can't seem to settle on one. This "path" is simply for display purposes and serves absolutely no purpose other than that. Here is what I have done to implement this "path." AFTER INSERT TRIGGER - requires passing a NULL path to the insert and updating the path for the record at the inserted rows identity INSTEAD OF INSERT TRIGGER - does not require insert to have NULL path passed, but does require the trigger to insert with a NULL path and updating the path for the record at SCOPE_IDENTITY() STORED PROCEDURE - requiring all inserts into this table to be done through the stored procedure implementing the trigger logic VIEW - requires building the path in the view 1 and 2 seem annoying if massive amounts of data are entered at once. 3 seems annoying because all inserts must go through the procedure in order to have a valid path populated. 1, 2, and 3 require maintaining a path column on the table. 4 removes all the limitations of the above but require the view to perform the path logic and requires use of the view if a path is to be displayed. I have successfully implemented all of the above approaches and I'm mainly looking for some advice. Am I way off the mark here or are any of the above acceptable? Each has it's advantages and disadvantages.

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• Discriminator based on joined property

  - by Andrew

  Suppose I have this relationship: abstract class Base { int Id; int JoinedId; ... } class Joined { int Id; int Discriminator; ... } class Sub1 : Base { ... } class Sub2 : Base { ... } for the following tables: table Base ( Id int, JoinedId int, ... ) table Joined ( Id int, Discriminator int, ... ) I would like to set up a table-per-hierarchy inheritance mapping for the Base, Sub1, Sub2 relationships, but using the Disciminator property from the Joined class as the discriminator. Here's the general idea for the mapping file: <class name="Base" table="Base"> <id name="Id"><generator class="identity"/></id> <discriminator /> <!-- ??? or <join> or <many-to-one>? --> <subclass name="Sub1" discriminator-value="1">...</subclass> <subclass name="Sub2" discriminator-value="2">...</subclass> </class> Is there any way of accomplishing something like this with the <discriminator>, <join>, or <many-to-one>? NHiberante seems to assume the discriminator is a column on the given table (which makes sense to me.. I know this is unorthodox). Thanks.

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• Speeding up inner-joins and subqueries while restricting row size and table membership

  - by hiffy

  I'm developing an rss feed reader that uses a bayesian filter to filter out boring blog posts. The Stream table is meant to act as a FIFO buffer from which the webapp will consume 'entries'. I use it to store the temporary relationship between entries, users and bayesian filter classifications. After a user marks an entry as read, it will be added to the metadata table (so that a user isn't presented with material they have already read), and deleted from the stream table. Every three minutes, a background process will repopulate the Stream table with new entries (i.e. whenever the daemon adds new entries after the checks the rss feeds for updates). Problem: The query I came up with is hella slow. More importantly, the Stream table only needs to hold one hundred unread entries at a time; it'll reduce duplication, make processing faster and give me some flexibility with how I display the entries. The query (takes about 9 seconds on 3600 items with no indexes): insert into stream(entry_id, user_id) select entries.id, subscriptions_users.user_id from entries inner join subscriptions_users on subscriptions_users.subscription_id = entries.subscription_id where subscriptions_users.user_id = 1 and entries.id not in (select entry_id from metadata where metadata.user_id = 1) and entries.id not in (select entry_id from stream where user_id = 1); The query explained: insert into stream all of the entries from a user's subscription list (subscriptions_users) that the user has not read (i.e. do not exist in metadata) and which do not already exist in the stream. Attempted solution: adding limit 100 to the end speeds up the query considerably, but upon repeated executions will keep on adding a different set of 100 entries that do not already exist in the table (with each successful query taking longer and longer). This is close but not quite what I wanted to do. Does anyone have any advice (nosql?) or know a more efficient way of composing the query?

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• Select multiple records from sql database table in a master-detail scenario

  - by Trex

  Hello, I have two tables in a master-detail relationship. The structure is more or less as follows: Master table: MasterID, DetailID, date, ... masterID1, detailID1, 2010/5/1, .... masterID2, detailID1, 2008/6/14, ... masterID3, detailID1, 2009/5/25, ... masterID4, detailID2, 2008/7/24, ... masterID5, detailID2, 2010/4/1, ... masterID6, detailID4, 2008/9/16, ... Details table: DetailID, ... detailID1, ... detailID2, ... detailID3, ... detailID4, ... I need to get all the records from the details table plus the LAST record from the master table (last by the date in the master table). Like this: detailID1, masterID1, 2010/5/1, .... detailID2, masterID5, 2010/4/1, ... detailID3, null, null, ... detailID4, masterID6, 2008/9/16, ... I have no idea how to do this. Can anybody help me? Thanks a lot. Jan

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• EF 6 Code First Many to many With Payload and self referencing many to many

  - by lesley86

  I Have the problem where i have a many to many relationship and on one of the tables there will be a self referencing many to many. So basically a school have zero or many groups and many groups can have 0 or many schools. The groups table will contain a parent child many to many with itself because a group can be a child of another group or it can have no children and that child can have a child, one child can also have many parents or a entity can have no parents. I created a mapping table with Payload to solvethe first many to many problem. code snippet public class School { public virtual ICollection<SchoolGroupMap> SchoolGroupMaps } public class SchoolGroup { public virtual ICollection<SchoolGroupMap> SchoolGroupMaps } public class SchoolGroupMap { public virtual School School public virtual SchoolGroup SchoolGroup } i Then tried modifying the code the following way for the the self referencing many to many public class SchoolGroup { public virtual ICollection<SchoolGroupMap> SchoolGroupMaps public virtual ICollection<SchoolGroup> Parents public virtual ICollection<SchoolGroup> Children } I changed the context with has many and an auto mapping table (forgive me i have been trying so many things today i do not have the exact code). I received an error the properties on the classes must match. Can anyone help please. I want to do create navigation properties on the self referencing many to many. Also a seed example would be appreciated regards

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• Reducing the opacity on a div without reducing the opacity of the contents

  - by user352744

  Want to reduce the opacity of page contents container background without reducing the opacity of the contents. <div id="container"> <div id="page contents"> page contents goes here, like amazing articles and all that. </div> </div> Needs to be able to expand with the content, thus can't have a fixed height. Absolute positioning it underneath the content will mean there will be no relationship between the two divs and it wont expand with the contents, so I think this is a dead end, feel free to say otherwise. Can't use Jquery as could be too laggy and not instant. Other options preferred please. May have to use 'png' background images but were hoping not to as it is a template and needs to be able to change colour based on colour schemes. Could generate images on demand but not ideal. Oh and to top it off cant use CSS3 as wont work in IE! of course! Any suggestions?

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