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• How Can I Reference Multiple Primary Keys For A Vector Type Primary Key

  - by AndreiC

  Hi, I have the following scenario: a table of projects and a table of persons, working on one or serveral projects. Also, I have a project id column (of type int), in the first table, which is a primary key there and I have a vector of project ids, as a column of type int, in my second table (persons), that references primary keys from the first table. What is the correct syntax for referencing multiple primary keys, from a vector foreign key. This is the way I am trying to create the table, but I am not sure what to place at the indicated line: CREATE TABLE Persons( Person_Id int, ..., ProjectsList int[], FOREIGN KEY (ProjectsList) REFERENCES Projects(Project_id) -- not sure what how to define the link here ); I hope my explanations are not over-complicated. Thank you in advance for helping!

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• git global config issue

  - by Andrew Bullock

  Somehow, my global git (msysgit) settings for user.name and user.email (and god knows what else) are set to a recent ex-colleague's details. When I try and change them i get could not commit to u://.gitconfig If I try and create u://.gitconfig through git bash then i get permission denied. C:\Users\<My Username>\ contains no references to git. I've tried uninstalling, searching the registry and my file system for all references to git and I can't find any (windows file search is crap though). What the hell is going on? Why even after reinstalling are this guys details still the global settings??? Thanks

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• JPA One to Many using JoinTable Error

  - by user553015

  I am trying to model 1:N (Person & Address) relationship using a junction table (Person_Address). 1.Person (personId PK) 2.Address (addressId PK) 3.PersonAddress ( personId, addressId composite PK, personId FK references Person, addressid FK references Address ) @Entity public class Person { @OneToMany @JoinTable( name="PersonAddress", joinColumns = @JoinColumn( name="personId"), inverseJoinColumns = @JoinColumn( name="addressId") ) public Set<Address> getAddresses() {...} ... } I encounter following error. Not able to find any solution. Caused by: org.hibernate.MappingException: Could not determine type for: com.realestate.details.Address, at table: Person, for columns: [org.hibernate.mapping.Column(address)] at org.hibernate.mapping.SimpleValue.getType(SimpleValue.java:269) at org.hibernate.mapping.SimpleValue.isValid(SimpleValue.java:253) at org.hibernate.mapping.Property.isValid(Property.java:185) at org.hibernate.mapping.PersistentClass.validate(PersistentClass.java:440) at org.hibernate.mapping.RootClass.validate(RootClass.java:192) at org.hibernate.cfg.Configuration.validate(Configuration.java:1108) at org.hibernate.cfg.Configuration.buildSessionFactory(Configuration.java:1293)

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• How to dynamically modify NHibernate load queries at runtime? EventListeners? Interceptors?

  - by snicker

  I need to modify the query used to load many-to-one references in my model. Specifically, I need to be able to further filter this data. Unfortunately, NH will not allow me to filter many-to-one relationships using the built in filtering system (?). I could just be doing something incorrect. Is there a hook where I can manually and dynamically modify the query used to load the data? Or an alternative to filters that will allow me to specify parameters? Background: I am working with a database that is using a form of revision control, with each entity having a natural ID PK, an EntityId, a RevisionValidTo and RevisionValidFrom field. There may be many rows using the same EntityId, which is the reference for other tables to join on, but the Revision ranges are mutually exclusive. Thus, the relationship is only many-to-one IIF the filter is applied. However, NH offers no way to specify a filter on many-to-one references (they do for collections...)

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• foreign key constraints on primary key columns - issues ?

  - by zzzeek

  What are the pros/cons from a performance/indexing/data management perspective of creating a one-to-one relationship between tables using the primary key on the child as foreign key, versus a pure surrogate primary key on the child? The first approach seems to reduce redundancy and nicely constrains the one-to-one implicitly, while the second approach seems to be favored by DBAs, even though it creates a second index: create table parent ( id integer primary key, data varchar(50) ) create table child ( id integer primary key references parent(id), data varchar(50) ) pure surrogate key: create table parent ( id integer primary key, data varchar(50) ) create table child ( id integer primary key, parent_id integer unique references parent(id), data varchar(50) ) the platforms of interest here are Postgresql, Microsoft SQL Server.

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• Creating a foreign key in MySQL produces error:

  - by SnOrfus

  I'm trying to create a foreign key on a table in MySQL and I'm getting a strange error that there seems to be little info about in any of my searches. I'm creating the key with this (emitted from mysql workbench 5.2): ALTER TABLE `db`.`appointment` ADD CONSTRAINT `FK_appointment_CancellationID` FOREIGN KEY (`CancellationID` ) REFERENCES `db`.`appointment_cancellation` (`ID` ) ON DELETE NO ACTION ON UPDATE NO ACTION , ADD INDEX `FK_appointment_CancellationID` (`CancellationID` ASC) ; at which point I get the error: ERROR 1452: Cannot add or update a child row: a foreign key constraint fails (alarmtekcore., CONSTRAINT FK_lead_appointment_CancellationID FOREIGN KEY (CancellationID) REFERENCES lead_appointment_cancellation (`) I've checked here but there's no data in the table.

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• How does Hibernate detect dirty state of an entity object?

  - by ???'Lenik

  Is it using some kind of byte codes modification to the original classes? Or, maybe Hibernate get the dirty state by compare the given object with previously persisted version? I'm having a problem with hashCode() and equals() methods for complicated objects. I feel it would be very slow to compute hash code if the object has collection members, and cyclic references are also a problem. If Hibernate won't use hashCode()/equals() to check the dirty state, I guess I should not use equals()/hashCode() for the entity object (not value object), but I'm also afraid if the same operator (==) is not enough. So, the questions are: How does Hibernate know if a property of an object is changed? Do you suggest to override the hashCode()/equals() methods for complicated objects? What if they contains cyclic references? And, also, Would hashCode()/equals() with only the id field be enough?

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• Vb6 project files and source safe

  - by Andrew

  A part of the application that I am working on is a legacy Vb6 Windows forms application. All the files in the project are under source control (VSS) except the Vb6 project file. From what I can establish from the other developers working on the project the reason for this is that the com components used in the projects have different references on each developers machine. I want to move the project files into VSS so that when files are added to the project these can be updated in the project files and other developers (and more importantly an automated build script) can get the latest project files from source safe. Does anyone know if/how I can achieve this in such a way as to not corrupt the references to other com components on different development machines?

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• Garbage Collection Java

  - by simion

  On the slides i am revising from it says the following; Live objects can be identified either by maintaining a count of the number of references to each object, or by tracing chains of references from the roots. Reference counting is expensive – it needs action every time a reference changes and it doesn’t spot cyclical structures, but it can reclaim space incrementally. Tracing involves identifying live objects only when you need to reclaim space – moving the cost from general access to the time at which the GC runs, typically only when you are out of memory. I understand the principles of why reference counting is expensive but do not understand what "doesn’t spot cyclical structures, but it can reclaim space incrementally." means. Could anyone help me out a little bit please? Thanks

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• Problem with assembly loading in .NET

  - by Jamie

  Hi guys, I have got two projects in my solution: Silverlight and standard one. The standard one references System.Xml assembly (version 4.0.0.0), however the Silverlight one references System.Xml assembly (v. 2.0.5.0). I want to make an instance of XmlWriter in my Silverlight project. Here comes the problem - the exception is thrown (file not found for System.Xml assembly). I believe it is a matter of different assembly versions. Do you have any idea how to resolve this issue? Ive read something about the binding redirection - is it the key to the solution? If so, how to do this? Thank you in advance for the reply! Cheers.

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• Specializating a template function that takes a universal reference parameter

  - by David Stone

  How do I specialize a template function that takes a universal reference parameter? foo.hpp: template<typename T> void foo(T && t) // universal reference parameter foo.cpp template<> void foo<Class>(Class && class) { // do something complicated } Here, Class is no longer a deduced type and thus is Class exactly; it cannot possibly be Class &, so reference collapsing rules will not help me here. I could perhaps create another specialization that takes a Class & parameter (I'm not sure), but that implies duplicating all of the code contained within foo for every possible combination of rvalue / lvalue references for all parameters, which is what universal references are supposed to avoid. Is there some way to accomplish this? To be more specific about my problem in case there is a better way to solve it: I have a program that can connect to multiple game servers, and each server, for the most part, calls everything by the same name. However, they have slightly different versions for a few things. There are a few different categories that these things can be: a move, an item, etc. I have written a generic sort of "move string to move enum" set of functions for internal code to call, and my server interface code has similar functions. However, some servers have their own internal ID that they communicate with, some use strings, and some use both in different situations. Now what I want to do is make this a little more generic. I want to be able to call something like ServerNamespace::server_cast<Destination>(source). This would allow me to cast from a Move to a std::string or ServerMoveID. Internally, I may need to make a copy (or move from) because some servers require that I keep a history of messages sent. Universal references seem to be the obvious solution to this problem. The header file I'm thinking of right now would expose simply this: namespace ServerNamespace { template<typename Destination, typename Source> Destination server_cast(Source && source); } And the implementation file would define all legal conversions as template specializations.

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• T-SQL Unique constraint locked the SQL server

  - by PaN1C_Showt1Me

  HI ! This is my table: CREATE TABLE [ORG].[MyTable]( .. [my_column2] UNIQUEIDENTIFIER NOT NULL CONSTRAINT FK_C1 REFERENCES ORG.MyTable2 (my_column2), [my_column3] INT NOT NULL CONSTRAINT FK_C2 REFERENCES ORG.MyTable3 (my_column3) .. ) I've written this constraint to assure that combination my_column2 and my_column3 is always unique. ALTER TABLE [ORG].[MyTable] ADD CONSTRAINT UQ_MyConstraint UNIQUE NONCLUSTERED ( my_column2, my_column3 ) But then suddenly.. The DB stopped responding.. there is a lock or something.. Do you have any idea why? What is bad with the constraint?

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• Calling member method on unmanaged C++ pointer from C# (I think)

  - by Jacob G

  I apologize in advance if this is a trivial question... I'm pretty C++ / unmanaged dumb. Here's a simplified analog to my setup: --In myUnmanagedObject.h in DLL: class myUnmanagedObject { public: virtual void myMethod(){} } --In MyControl.h in Assembly #1: #pragma make_public(myUnmanagedObject) [event_source(managed)] public ref class MyControl : public System::Windows::Forms::UserControl { public: myUnmanagedObject* GetMyUnmanagedObject(); } --in C# in Assembly #2: unsafe { MyControl temp = new MyControl(); myUnmanagedObject* obj = temp.GetMyUnmanagedObject(); obj-myMethod(); } I get a compile error saying that myUnmanagedObject does not contain a definition for myMethod. Assembly #2 references Assembly #1. Assembly #1 references DLL. If I compile the DLL with /clr and reference it directly from Assembly #2, it makes no difference. How, from C#, do I execute myMethod ?

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• MySQL Removing Some Foreign keys

  - by Drew

  I have a table whose primary key is used in several other tables and has several foreign keys to other tables. CREATE TABLE location ( locationID INT NOT NULL AUTO_INCREMENT PRIMARY KEY ... ) ENGINE = InnoDB; CREATE TABLE assignment ( assignmentID INT NOT NULL AUTO_INCREMENT PRIMARY KEY, locationID INT NOT NULL, FOREIGN KEY locationIDX (locationID) REFERENCES location (locationID) ... ) ENGINE = InnoDB; CREATE TABLE assignmentStuff ( ... assignmentID INT NOT NULL, FOREIGN KEY assignmentIDX (assignmentID) REFERENCES assignment (assignmentID) ) ENGINE = InnoDB; The problem is that when I'm trying to drop one of the foreign key columns (ie locationIDX) it gives me an "ERROR 1025 (HY000): Error on rename" error. How can I drop the column in the assignment table above without getting this error?

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• Garbage Collection in Java

  - by simion

  On the slides I am revising from it says the following: Live objects can be identified either by maintaining a count of the number of references to each object, or by tracing chains of references from the roots. Reference counting is expensive – it needs action every time a reference changes and it doesn’t spot cyclical structures, but it can reclaim space incrementally. Tracing involves identifying live objects only when you need to reclaim space – moving the cost from general access to the time at which the GC runs, typically only when you are out of memory. I understand the principles of why reference counting is expensive but do not understand what "doesn’t spot cyclical structures, but it can reclaim space incrementally." means. Could anyone help me out a little bit please? Thanks

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• How to run SpecFlow tests in Visual Studio 2010?

  - by testerboy

  Trying to get SpecFlow running with a fresh VS2010 Professional install. Created a new console application and added references to NUnit and SpecFlow. Created a SpecFlow feature. The .feature with the default template code is created. Now I try to run this test, but I don't understand how. When I right-click the project (at the top-level), there is no "Run test(s)" option in the mouse drop down menu. Didn't the SpecFlow install correctly, am I missing some references or some other tool I need to install?

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• C++: Cannot convert from foo& to foo*

  - by Rosarch

  I have a method: odp(foo& bar); I'm trying to call it: foo baz; odp(&baz); I get a compiler error: error C2664: "odp" cannot convert parameter 1 from 'foo *' to 'foo &' What am I doing wrong? Aren't I passing in a reference to baz? UPDATE: Perhaps I have a misconception about the relationship between pointers and references. I thought that they were the same, except references couldn't be null. Is that incorrect?

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• Rails 3 Join Question for Votes Table

  - by Dex

  I have a table posts and a polymorphic table votes. The votes table looks like this: create_table :votes do |t| t.references :user # user_id t.vote # the vote value t.references :votable # votable_type and votable_id end I want to list all posts that the user has not yet voted on. Right now I'm basically taking all the posts they've already voted on and subtracting that from the entire set of posts. It works but it's not very convenient as I currently have it. def self.where_not_voted_on_by(user) sql = "SELECT P.* FROM posts P LEFT OUTER JOIN (" sql << where_voted_on_by(user).to_sql sql << ") ALREADY_VOTED_FOR ON P.id = ALREADY_VOTED_FOR.id WHERE (user_id is null)" puts sql resultset = connection.select_all(sql) results = [] resultset.each do |r| results << Post.new(r) end results end def self.where_voted_on_by(user) joins(:votes.outer).where("user_id = #{user.id}").select("posts.*, votes.user_id") end

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• Does lookaround affect which languages can be matched by regular expressions?

  - by sepp2k

  There are some features in modern regex engines which allow you to match languages that couldn't be matched without that feature. For example the following regex using back references matches the language of all strings that consist of a word that repeats itself: (.+)\1. This language is not regular and can't be matched by a regex, which does not use back references. My question: Does lookaround also affect which languages can be matched by a regular expression? I.e. are there any languages that can be matched using lookaround, which couldn't be matched otherwise? If so, is this true for all flavors of lookaround (negative or positive lookahead or lookbehind) or just for some of them?

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• C++ IDE for Linux with smart reference searching

  - by Dmitry Yudakov

  Is there an IDE supporting C++ with REALLY smart searching of references? By 'reference' I mean usage of a class (or its member), variable, function in the whole Project or Workspace. There's lots of IDE providing it. Some of them seem just to search for the text with same name giving lots of stuff, others are smarter and check the context (like class boundaries, namespace) but aren't accurate enough. The best I've tried so far was Visual SlickEdit, but still there's more to wish. class C1 { int foo; }; class C2 { int foo; }; For example in this situation when searching for C1::foo references I don't want C2::foo to be shown too. So, is there an IDE that would be so smart?

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• Conditional Logistic Regression - detailed examples

  - by op

  Hi, anyone has online resources / book references that has detailed tutorials/examples on setting up Conditional Logistic Regression ? (Preferably in R, Matlab or Python)

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• Using the same modules in multiple projects

  - by Andreas Vinther

  I'm using Visual Studio 2010 and coding in VB.NET. My problem is that I've collected all the modules I've written and intend to reuse and placed them in a separate folder. When I want to add a module from the above folder to any given project, it takes a copy of the module and places in the project's source code folder, instead of referencing the module in the folder containing all the other modules. Is it possible to include a module in my project and leave it in the folder with all the other modules, so that when I improve upon a module, it'll affect all the projects that uses/references that module. Instead of me having to manually copy the new module to all the projects that uses/references the module. Right now I have multiple instances of the exact same module that i need to update manually when I improve code or add functionality?

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• SQL HAVING COUNT and JOIN

  - by user1833274

  I have tried to this query: What are the doctors that work on less than 2 Hospitals. I have these tables: CREATE TABLE Hospital ( hid INT PRIMARY KEY, name VARCHAR(127) UNIQUE, country VARCHAR(127), area INT ); CREATE TABLE Doctor ( ic INT PRIMARY KEY, name VARCHAR(127), date_of_birth INT, ); CREATE TABLE Work ( hid INT, ic INT, since INT, FOREIGN KEY (hid) REFERENCES Hospital (hid), FOREIGN KEY (ic) REFERENCES Doctor (ic), PRIMARY KEY (hid,ic) ); I tried with this: SELECT DISTINCT D.ic FROM Doctor D, Work W JOIN Hospital H ON (H.hid = W.hid) WHERE D.bi = W.bi GROUP BY (D.ic) HAVING COUNT(H.hid) < 2 ;

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• Stop invalid data in a attribute with foreign key constraint using triggers?

  - by Eternal Learner

  How to specify a trigger which checks if the data inserted into a tables foreign key attribute, actually exists in the references table. If it exist no action should be performed , else the trigger should delete the inserted tuple. Eg: Consider have 2 tables R(A int Primary Key) and S(B int Primary Key , A int Foreign Key References R(A) ) . I have written a trigger like this : Create Trigger DelS BEFORE INSERT ON S FOR EACH ROW BEGIN Delete FROM S where New.A <> ( Select * from R;) ); End; I am sure I am making a mistake while specifying the inner sub query within the Begin and end Blocks of the trigger. My question is how do I make such a trigger ?

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• Visaul Studio 2010, TlbImp generates .net 4.0 interops in 2.0 projects

  - by DJScrib

  In a C# project we add a reference to a COM object via the Add References setup pointing to a COM object which results in the IDE auto-generating the interop assembly. So this is fine and good, but we are building based on .net 3.5 SP1 aka CLR 2.0, and the generated interops are using the 4.0 CLR making them incompatiable. Is there a way to prevent this? I assume the other option is in our build script to try using tlbimp.exe with the /references parameter? to point to mscorlib v2.0? Anyhow, I'm hoping there's a flag somewhere to allow this.

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