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• Deleting orphans with JPA

  - by homaxto

  I have a one-to-one relation where I use CascadeType.PERSIST. This has over time build up a huge amount of child records that has not been deleted, to such an extend that it is reflected in the performance. Now I wish to add some code that cleans up the database removing all the child records that are not referenced by a parent. At the moment we are talking 400K+ records, at I need to run the code on all customer installations just to be sure they do not run into the same problem. I think the best solution would be to run a named query (because we support two databases) that deletes the necessary records, and this is where I get into problems, because how should I write it in JPQL? The result I want can be defined like the following sql statement, which unfortunaltely does not run on MySQL. DELETE FROM child c1 WHERE c1.pk NOT IN (SELECT DISTINCT p.pk FROM child c2 JOIN parent p ON p.child = c2.pk);

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• C++ Operator overloading - 'recreating the Vector'

  - by Wallter

  I am currently in a collage second level programing course... We are working on operator overloading... to do this we are to rebuild the vector class... I was building the class and found that most of it is based on the [] operator. When I was trying to implement the + operator I run into a weird error that my professor has not seen before (apparently since the class switched IDE's from MinGW to VS express...) (I am using Visual Studio Express 2008 C++ edition...) Vector.h #include <string> #include <iostream> using namespace std; #ifndef _VECTOR_H #define _VECTOR_H const int DEFAULT_VECTOR_SIZE = 5; class Vector { private: int * data; int size; int comp; public: inline Vector (int Comp = 5,int Size = 0) : comp(Comp), size(Size) { if (comp > 0) { data = new int [comp]; } else { data = new int [DEFAULT_VECTOR_SIZE]; comp = DEFAULT_VECTOR_SIZE; } } int size_ () const { return size; } int comp_ () const { return comp; } bool push_back (int); bool push_front (int); void expand (); void expand (int); void clear (); const string at (int); int operator[ ](int); Vector& operator+ (Vector&); Vector& operator- (const Vector&); bool operator== (const Vector&); bool operator!= (const Vector&); ~Vector() { delete [] data; } }; ostream& operator<< (ostream&, const Vector&); #endif Vector.cpp #include <iostream> #include <string> #include "Vector.h" using namespace std; const string Vector::at(int i) { this[i]; } void Vector::expand() { expand(size); } void Vector::expand(int n ) { int * newdata = new int [comp * 2]; if (*data != NULL) { for (int i = 0; i <= (comp); i++) { newdata[i] = data[i]; } newdata -= comp; comp += n; delete [] data; *data = *newdata; } else if ( *data == NULL || comp == 0) { data = new int [DEFAULT_VECTOR_SIZE]; comp = DEFAULT_VECTOR_SIZE; size = 0; } } bool Vector::push_back(int n) { if (comp = 0) { expand(); } for (int k = 0; k != 2; k++) { if ( size != comp ){ data[size] = n; size++; return true; } else { expand(); } } return false; } void Vector::clear() { delete [] data; comp = 0; size = 0; } int Vector::operator[] (int place) { return (data[place]); } Vector& Vector::operator+ (Vector& n) { int temp_int = 0; if (size > n.size_() || size == n.size_()) { temp_int = size; } else if (size < n.size_()) { temp_int = n.size_(); } Vector newone(temp_int); int temp_2_int = 0; for ( int j = 0; j <= temp_int && j <= n.size_() && j <= size; j++) { temp_2_int = n[j] + data[j]; newone[j] = temp_2_int; } //////////////////////////////////////////////////////////// return newone; //////////////////////////////////////////////////////////// } ostream& operator<< (ostream& out, const Vector& n) { for (int i = 0; i <= n.size_(); i++) { //////////////////////////////////////////////////////////// out << n[i] << " "; //////////////////////////////////////////////////////////// } return out; } Errors: out << n[i] << " "; error C2678: binary '[' : no operator found which takes a left-hand operand of type 'const Vector' (or there is no acceptable conversion) return newone; error C2106: '=' : left operand must be l-value As stated above, I am a student going into Computer Science as my selected major I would appreciate tips, pointers, and better ways to do stuff :D

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• Can someone describe some DI terms to me?

  - by SoBeNoFear

  I'm in the process of writing a DI framework for PHP 5, and I've been trying to find the 'official' definitions of some words in relation to dependency injection. Some of these words are 'context' and 'lifecycle'. And also, what would I call the object that gets created/injected? Finally, what is the difference between components and services, and which term (if either) should I call the objects that can be injected? I've read Martin Fowler's article and looked through other DI frameworks (Phemto, Spring, Google Guice, Xyster, etc.), but I want to know what you think. Thanks!

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• SQL join to grab data from same table via intermediate table

  - by Sergio

  Hi Could someone help me with building the following query. I have a table called Sites, and one called Site_H. The two are joined by a foreign key relationship on page_id. So the Sites table contains pages, and the Site_H table shows which pages any given page is a child of by having another foreign key relation back to the site table with a column called ParentOf. So, a page can be have another page as a parent. Other data is stored in the Site_H table such as position etc, hence why it is separated out. I would like a query that returns the details of a page along with the details of its parent page. I just cant quite think about how to structure the SQL. Thanks

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• Same table NHibernate mapping

  - by mircea .

  How can i go about defining a same table relation mapping (mappingbycode) using Nhibernate for instance let's say I have a class: public class Structure{ public int structureId; public string structureName; public Structure rootStructure; } that references the same class as rootStructure. mapper.Class<Structure>(m => { m.Lazy(true); m.Id(u => u.structureId, map => { map.Generator(Generators.Identity); }); m.Property(c => c.structureName); m.? // Same table mapping } ; Thanks

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• Filtering foreign keys with AJAX in Django admin

  - by cnobile

  I have most of this figured out already. I have AJAX returning the region/state/province when a country is selected. The correct foreign key is saved to the database, however, when the record is viewed afterwards the selected state is not shown in the select nor are any states for the selected country. I understand why this is happening as, the admin view is not aware of the relation between the state and the country. So here is the question. Is there a hook in the admin view that will allow me to load the correct states for the country and set the selected attribute on the option in the select tag? Or how can I override the admin view for any forms that require the country and region/state/province set? I am using jQuery and Djando-1.1. Thanks

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• Help me refactoring this nasty Ruby if/else statement

  - by Suborx

  Hello, so I have this big method in my application for newsletter distribution. Method is for updating rayons and i need to assigned user to rayon. I have relation n:n through table colporteur_in_rayons witch have attributes since_date and _until_date. I am junior programmer and i know this code is pretty dummy :) I appreciated every suggestion. def update rayon = Rayon.find(params[:id]) if rayon.update_attributes(params[:rayon]) if params[:user_id] != "" unless rayon.users.empty? unless rayon.users.last.id.eql?(params[:user_id]) rayon.colporteur_in_rayons.last.update_attributes(:until_date = Time.now) Rayon.assign_user(rayon.id,params[:user_id]) flash[:success] = "Rayon #{rayon.name} has been succesuly assigned to #{rayon.actual_user.name}." return redirect_to rayons_path end else Rayon.assign_user(rayon.id,params[:user_id]) flash[:success] = "Rayon #{rayon.name} has been successfully assigned to #{rayon.actual_user.name}." return redirect_to rayons_path end end flash[:success] = "Rayon has been successfully updated." return redirect_to rayons_path else flash[:error] = "Rayon has not been updated." return redirect_to :back end end

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• Seaching for an element in a circular sorted array

  - by guirgis

  I wanted to share this with you, i had this problem in a google interview. we want to search for a given element in a circular sorted array in complexity not greater than O(Log n). ex: search for 13 in {5,9,13,1,3}. My idea was to convert the circular array into a regular sorted array then do a binary search on the resulting array, but my problem was the algorithm i came up was stupid that it takes O(n) in the worst case: for(i = 1; i < a.length; i++){ if (a[i] < a[i-1]){ minIndex = i; break; } } then the corresponding index of ith element will be determined from the following relation: (i + minInex - 1) % a.length it is clear that my conversion (from circular to regular) algorithm may take O(n), so we need a better one, any suggestions?

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• Symfony2 : How to make the php_intl extension available for Symfony2?

  - by Miles M.

  I'm trying to follow this documentation on Symfony : http://symfony.com/doc/current/book/forms.html ok so here is my thing, I've externalised my form and created a specific form class for handling the process and being able to reuse it. So what happen when I submit the form, whatever the info are okay or not for my class, I get this fatal Error : Fatal error: Call to a member function setAttribute() on a non-object in C:\Program Files (x86)\wamp\www\QNetworks\vendor\symfony\src\Symfony\Component\Form\Extension\Core\DataTransformer\NumberToLocalizedStringTransformer.php on line 130 Call Stack I'm running with php 5.3.9 and my intl extension is installed and activated BUT when I run the app/check.php command I see : [[WARNING]] Checking that the intl extension is available: FAILED * Install and enable the intl extension (used for validators) * So I don't understand what the problem with this extension. Should I reinstall it ? When I go here : http://php.net/manual/en/intl.requirements.php I see tht i can install the PECL or the ICU library, but i don't know if I should and if there is any relation with my problem .. Thank for your help !!

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• Updating records in Postgres using FROM clause

  - by Summer

  Hi, I'm changing my db schema, and moving column 'seat' from old_table to new_table. First I added a 'seat' column to new_table. Now I'm trying to populate the column with the values from old_table. UPDATE new_table SET seat = seat FROM old_table WHERE old_table.id = new_table.ot_id; This returns ERROR: column reference "seat" is ambiguous. UPDATE new_table nt SET nt.seat = ot.seat FROM old_table ot WHERE ot.id = nt.ot_id; Returns ERROR: column "nt" of relation "new_table" does not exist Ideas?

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• Retreive list of students registered for a particular course

  - by Pankaj Khurana

  Hi, I have moodle1.9 installed on my system and writing some custom reports. I want to retrieve list of students registered for a particular course. I have user profile field usercategoryid through which i figure out for which category he has enrolled. Course belongs to a particular category. Through mdl_user_info_data table i retrieve the category for a particular user. I have written a query to retrieve the users who have registered for a particular category for e.g. Financial Planning 2010. But the issue is that i now want users who have registered for a particular course for e.g. Insurance Planning. There is a relation between course and course category but i am unable to find out the table where course and user information is linked. Please help me on this Thanks

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• how to query with child relations to same table and order this correctly

  - by robertpnl

  Hi, Take this table: id name sub_id --------------------------- 1 A (null) 2 B (null) 3 A2 1 4 A3 1 The sub_id column is a relation to his owm table, to column ID. subid --- 0:1 --- id Now I have the problem to make a correctly SELECT query to show that the child rows (which sub_id is not null) directly selected under his parent row. So this must be a correctly order: 1 A (null) 3 A2 1 4 A3 1 2 B (null) A normal SELECT order the id. But how or which keyword help me to order this correctly? JOIN isn't possible I think because I want to get all the rows seperated. Because the rows will be displayed on a Gridview (ASP.Net) with EntityDataSource but the child rows must be displayed directly under his parent. Thank you.

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• Quering distinct values throught related model

  - by matheus.emm

  Hi! I have a simple one-to-many (models.ForeignKey) relationship between two of my model classes: class TeacherAssignment(models.Model): # ... some fields year = models.CharField(max_length=4) class LessonPlan(models.Model): teacher_assignment = models.ForeignKey(TeacherAssignment) # ... other fields I'd like to query my database to get the set of distinct years of TeacherAssignments related to at least one LessonPlan. I'm able to get this set using Django query API if I ignore the relation to LessonPlan: class TeacherAssignment(models.Model): # ... model's fields def get_years(self): year_values = self.objects.all().values_list('year').distinct().order_by('-year') return [yv[0] for yv in year_values if len(yv[0]) == 4] Unfortunately I don't know how to express the condition that the TeacherAssignment must be related to at least one LessonPlan. Any ideas how I'd be able to write the query? Thanks in advance.

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• Orphan Char appearing when using Sifr3 in Navigation (Wordpress)

  - by missmonkee

  Hi there, I am having an issue implementing Sifr3 on this particular site and it's driving me nuts. Hoping someone will be able to help me: http://client.missmonkee.com/agency-mobile LOGIN: client-login cl1entpassw0rd Here at the top right you can see the navigation to the site, in FF3 Win 7 / FF & Safari MAC some menu items show 1 char on a seperate line to the rest of the menu item. It looks as if there is a width on the li or something but I'm 100% sure there isnt and the rest of the menu items are OK and display fine. Something in relation to this might help answer this problem, is that Sifr3 does does not work AT ALL in IE7 WIN. I've checked previous answers to this, being the trailing comma issue but I've triple checked and I do not have any trailing commas. Can anyone help on this pls? Thanks in advance

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• Rails Nested Attributes, Relationship for Shared or Common Object

  - by SooDesuNe

  This has to be a common problem, so I'm surprised that Google didn't turn up more answers. I'm working on a rails app that has several different kinds of entities, those entities by need a relation to a different entity. For example: Address: a Model that stores the details of a street address (this is my shared entity) PersonContact: a Model that includes things like home phone, cell phone and email address. This model needs to have an address associated with it DogContact: Obviously, if you want to contact a dog, you have to go to where it lives. So, PersonContact and DogContact should have foreign keys to Address. Even, though they are really the "owning" object of Address. This would be fine, except that accepts_nested_attributes_for is counting on the foreign key being in Address to work correctly. What's the correct strategy to keep the foreign key in Address, but have PersonContact and DogContact be the owning objects?

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• Can someone please explain to me the basic function of Intents in the Android OS?

  - by K-RAN

  I'm new to programming applications for the Android OS. As far as general architecture of the OS goes, I understand that processes are implemented as Linux processes and that each one is sandboxed. However, I'm utterly confused on the IPCs and syscalls (if any) used. I know that the IBinder is a form of this; parcels are sent back and forth between processes and Bundles are array forms of parcels (?). But even that is still unfamiliar to me. Same with Intents. All in all, I don't understand what kinds of IPCs are implemented and how. Could someone briefly explain to me the specific methods used by user level applications in Android OS to communicate with each other and the OS? I've done kernel programming and played with various IPCs in Linux (Ubuntu and Debian) so it would help immensely if this was all explained in relation to what I'm familiar with... Thanks in advance!

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• Express highest floating point quantity that is less than 1

  - by edA-qa mort-ora-y

  I was doing some rounding calculations and happened upon a question. How can I express the highest quantity less than 1 for a given floating point type? That is, how I write/represent value x such that x < 1, x + y >= 1 for any y > 0. In fractions this would be x = (q-1)/q where q is the precision of the type. For example, if you are counting in 1/999 increments then x = 998/999. For a given type (float, double, long double), how could one express the value x in code? I also wonder if such a value actually exists for all values of y. That is, as y's exponent gets smaller perhaps the relation doesn't hold anymore. So an answer with some range restriction on y is also acceptable. (The value of x I want still does exist, the relationship may just not properly express it.)

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• Search filenames in MySQL database table restricted by filetype?

  - by ju

  Hello I have a MySQL database that I replicate from another server. The database contains a table with this columns ID, FileName and FileSize In the table there are more than 4'000'000 records. I want to make fast a search in FileName (varchar) column I found that I can use for this Sphinx search engine. The problem is that I want to restrict searches by filetype. Do I have to and how (trigers?) to extract file extensions for all rows? May be I have to create another table (because this one is replicated) and join them in 1:1 relation? Can you give me some advices please :)

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• django getting current user id

  - by dana

  hello, i have a mini app where users can login, view their profile, and follow each other. 'Follow' is a relation like a regular 'friend' relationship in virtual communities, but it is not necessarily reciprocal, meaning that one can follow a user, without the need that the user to be following back that person who follows him. my problem is: if i am a logged in user, and i navigate to a profile X, and push the button follow, how can i take the current profile id ?(current profile meaning the profile that I, the logged in user, am viewing right now.) the view: def follow(request): if request.method == 'POST': form = FollowForm(request.POST) if form.is_valid(): new_obj = form.save(commit=False) new_obj.initiated_by = request.user u = User.objects. what here? new_obj.follow = u new_obj.save() return HttpResponseRedirect('.') else: form = FollowForm() return render_to_response('followme/follow.html', { 'form': form, }, context_instance=RequestContext(request)) thanks in advance!

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• Best Dijkstra papers to explain this quote?

  - by jemfinch

  I was enjoying "The Humble Programmer" earlier today and ran across this choice quote: Therefore, for the time being and perhaps forever, the rules of the second kind present themselves as elements of discipline required from the programmer. Some of the rules I have in mind are so clear that they can be taught and that there never needs to be an argument as to whether a given program violates them or not. Examples are the requirements that no loop should be written down without providing a proof for termination nor without stating the relation whose invariance will not be destroyed by the execution of the repeatable statement. I'm looking for which of Dijkstra's 1300+ writings best describe in further detail rules such as he was describing above.

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• Exception while trying to deserialize JSON into EntityFramework using JavaScriptSerializer

  - by Barak

  I'm trying to deserialize JSON which I'm getting from an external source into an Entity Framework entity class using the following code: var serializer = new JavaScriptSerializer(); IList<Feature> obj = serializer.Deserialize<IList<Feature>>(json); The following exception is thrown: Object of type 'System.Collections.Generic.List1[JustTime.Task]' cannot be converted to type 'System.Data.Objects.DataClasses.EntityCollection1[JustTime.Task]'. My model is simple: The Feature class has a one-to-many relation to the Tasks class. The problem appears to be the deserializer is trying to create a generic List to hold the collection of tasks instead of an EntityCollection. I've tried implementing a JavaScriptConverted which would handle System.Collections.Generic.List but it didn't get called by the deserializer.

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• Upgrade Oracle database from 9.2.0.7 to 9.2.0.8

  - by b_dws

  We are planning to upgrade from Oracle 9.2.0.7 to 9.2.0.8. Main reason of the proposed upgrade is to address the issue in relation to exception "terminated with error: ORA-00904: "T2"."SYS_DS_ALIAS_4": invalid identifier" when we try to execute DBMS_STATS.GATHER_SCHEMA_STATS. We are concerned that the proposed upgrade may have negative impact on our Java application or in the worst case may not even support by our Java application. What are the possible approaches or strategies that we can take to ensure the upgrade from Oracle 9.2.0.7 to 9.2.0.8 will not have adverse impact on our Java application or will not cause our Java application to function incorrectly. Essentially we just want to confirm that our application will still support Oracle 9.2.0.8. Thank you.

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• Entity Framework 4 code-only reference column name

  - by Victor

  I created classes: public class Country { public long CountryId {get;set;} public string CountryName {get;set;} } public class Profile { public long ProfileId {get;set;} public string ProfileName {get;set;} public Country Country {get;set;} } and configuration for Profile: public class ProfileConfiguration : EntityConfiguration<Profile> { public IlluminatiCoreProfileConfiguration() { Relation(p => p.Country); } } Then I create context and run context.CreateDatabase(). New database contains table Profiles with column Country_CountryId. How can I write configuration for changing column name to "CountryId"? Thanks.

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• Is it possible to listen to relational database update?

  - by Morgan Cheng

  Is it possible to listen to relation database update? For example, my web app want to send data update to client through Comet technology. I can have the program to poll the database periodically, but that would not be performant and scalable. If app can hood to a "event handler" of database, then app can get notification every time given database table data is updated. This sounds more promising, but I didn't find any concrete example for it. This is listener pattern. Does common relational database support such feature?

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• Best way to order menu items injected by an IoC/plugin Framework

  - by Daver

  One of the common things I've seen done in applications built on IoC/plugin frameworks is to add commands to menus or toolbars from the dynamically loaded plugins. For example, the application's default plugins supply actions like "New, Open, Save" that show up in the context menu for a certain item in the workspace. A new plugin may add "Mail, Post, Encrypt" commands, but where do those commands show up in relation to "New, Open, Save"? How can the application that is loading components through IoC impose order on the items that get injected? Does it require metadata from the plugins that give a hint on how to group or order the items? Does it use a config file of previously known menu names (or ids) to define the order (seems a little weak to me)? Or are "unknown" plugins treated as second class citizens and always get dumped into sub menus? Something I've never even imagined (which I'm hoping to see in the answers)

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