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• Querying my JPA provider (Hibernate) for a collection of <Id,Name> of an entity

  - by Ittai

  Hi, I have an entity which looks something like this: Id (PK) Name Other business properties and associations... I have the need for my DAL (JPA with hibernate as provider) to return a list of the entities which correlate to some constraints (or just return them all) but instead of returning the entities themselves I'd like to receive only the Id and the Name properties. I know this can be achieved with HQL/SQL (something like: select id,name from entity where...) but I don't want to go down that road. I was thinking of somehow defining the pair a compositioned part of the entity and thought that might help me but I'm not sure that's "legal" as the Id is the PK. The logic for this scenario is to have a textbox which asynchronously queries the web-service (and through it the DAL) for the relevant entities and once an entity is selected then it is loaded as a whole and shipped to the front-end. Would appreciate any feedback, Ittai

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• Large Video Uploads via a website

  - by Andrew

  Some of the problems that can happen are timeouts, disconnections, and not being able to resume a file and having to start from the beginning. Assuming these files are up to around 5gigs in size, what is the best solution for dealing with this problem? I'm using a Drupal 6 install for the website. Some of my constraints due to the server setup I have to deal with: Shared hosting with max 200 connections at a time (unlimited disk space) Shared hosting. Unable to create users through an API (so can't automatically generate ftp accounts) I do have the ability to run cron-type scripts via a Drupal module. My initial thought was to create ftp users based off of Drupal accounts and requiring them to download an ftp client for their OS of choice. But the lack of API to auto-create ftp accounts and the inability to do it from command line kind of hinder that solution. If there's a workaround someone can think of, let me know! Thanks

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• Right design to validate attributes of a class instance

  - by systempuntoout

  Having a simple Python class like this: class Spam(object): __init__(self, description, value): self.description = description self.value = value Which is the correct approach to check these constraints: "description cannot be empty" "value must be greater than zero" Should i: 1.validate data before creating spam object ? 2.check data on __init__ method ? 3.create an is_valid method on Spam class and call it with spam.isValid() ? 4.create an is_valid static method on Spam class and call it with Spam.isValid(description, value) ? 5.check data on setters? 6.... Could you recommend a well designed\Pythonic\not verbose (on class with many attributes)\elegant approach?

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• How to refresh database data only in SQL Server

  - by MaxGeek

  So I want to copy just the data from a Prod database (SQL 2005) down to my local machine (SQL 2005 & SQL 2008 Management Studio installed). The problem is I'm running into foreign key constraints that are causing the task/scripts to fail. I can get by these errors if I import certain tables first, but is there an easier way to do this all at once? I'm not a DBA so I don't have access to the database back up. I've tried the SQL Import/Export data Wizard and Publishing Wizard, but it also gets the PK error.

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• Errors not being redirected to an Http handler if redirectMode="ResponseRewrite"

  - by Luk

  I see similar questions, but it looks like there were due to an unrelated issue. in 3.5, I have a custom error handler that logs errors and redirects users. My web.config is set up as such: <httpHandlers> <add path="error.ashx" type="MySite.Tools.WebErrorLogger, MySite.Tools" verb="*"/> </httpHandlers> <customErrors mode="On" defaultRedirect="error.ashx" redirectMode="ResponseRewrite"> </customErrors> When redirectMode is set to "ResponseRedirect", everything works fine (but Server.GetLastError() being null but that seems to be intended) However, when using ResponseRewrite, my handler is not called and I see ASP.Net default error pages. Any idea on how I could do this? (I unfortunately can't use either an aspx page or do my error handling in global.asax due to other constraints)

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• Haskell: Constrain function on type Double to only work with Integers

  - by thurn

  Suppose I'm writing a function that takes a list of integers and returns only those integers in the list that are less than 5.2. I might do something like this: belowThreshold = filter (< 5.2) Easy enough, right? But now I want to constrain this function to only work with input lists of type [Int] for design reasons of my own. This seems like a reasonable request. Alas, no. A declaration that constraints the types as so: belowThreshold :: [Integer] -> [Integer] belowThreshold = filter (< 5.2) Causes a type error. So what's the story here? Why does doing filter (< 5.2) seem to convert my input list into Doubles? How can I make a version of this function that only accepts integer lists and only returns integer lists? Why does the type system hate me?

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• How can I improve my programming skills with out a computer (or reading material)?

  - by Tom Duckering

  Given the recent and continued chaos with grounded flights and folks stuck in airports, and what not, I'm wondering if anyone has any suggestions for activities that would help sharpen and develop a progammer's mind. The constraints are: Laptop is out of battery and there are no free sockets. You're bored of the book you're reading or you have none with you. Reasonable resources such as a pen and pad of paper are available. Rules can be bent within reason. As daft examples, things I have thought about are: How I might optimise the boarding of a plane. How I might improve the UI of a departure board.

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• Play 2.0 javaToDo tutorial doesn't compile

  - by chsn

  I'm trying to follow the Play2.0 JavaToDO tutorial and for some reason it just doesn't want to work. Have looked through stackoverflow and other online resources, but haven't find an answer to this and it's driving me crazy. Attached code of the Application.java package controllers; import models.Task; import play.data.Form; import play.mvc.Controller; import play.mvc.Result; public class Application extends Controller { static Form<Task> taskForm = form(Task.class); public static Result index() { return redirect(routes.Application.tasks()); } public static Result tasks() { return ok( views.html.index.render(Task.all(), taskForm)); } public static Result newTask() { return TODO; } public static Result deleteTask(Long id) { return TODO; } } Attached code of the Task java package models; import java.util.List; import javax.persistence.Entity; import play.data.Form; import play.data.validation.Constraints.Required; import play.db.ebean.Model.Finder; import play.mvc.Result; import controllers.routes; @Entity public class Task { public Long id; @Required public String label; // search public static Finder<Long,Task> find = new Finder( Long.class, Task.class); // display tasks public static List<Task> all() { return find.all(); } // create task public static void create(Task task) { task.create(task); } // delete task public static void delete(Long id) { find.ref(id).delete(id); // find.ref(id).delete(); } // create new task public static Result newTask() { Form<Task> filledForm = taskForm.bindFromRequest(); if(filledForm.hasErrors()) { return badRequest( views.html.index.render(Task.all(), filledForm) ); } else { Task.create(filledForm.get()); return redirect(routes.Application.tasks()); } } } I get a compile error on Task.java on the line static Form<Task> taskForm = form(Task.class); As I'm working on eclipse (the project is eclipsified before import), it's telling me that taskForm cannot be resolved and it also underlines every play 2 command e.g. "render(), redirect(), bindFromRequest()" asking me to create a method for it. Any ideas how to solve the compilations error and also how to get Eclipse to recognize the play2 commands? EDIT: updated Application.java package controllers; import models.Task; import play.data.Form; import play.mvc.Controller; import play.mvc.Result; public class Application extends Controller { // create new task public static Result newTask() { Form<Task> filledForm = form(Task.class).bindFromRequest(); if(filledForm.hasErrors()) { return badRequest( views.html.index.render(Task.all(), filledForm) ); } else { Task.newTask(filledForm.get()); return redirect(routes.Application.tasks()); } } public static Result index() { return redirect(routes.Application.tasks()); } public static Result tasks() { return ok( views.html.index.render(Task.all(), taskForm)); } public static Result deleteTask(Long id) { return TODO; } } Updated task.java package models; import java.util.List; import javax.persistence.Entity; import play.data.Form; import play.data.validation.Constraints.Required; import play.db.ebean.Model; import play.db.ebean.Model.Finder; import play.mvc.Result; import controllers.routes; @Entity public class Task extends Model { public Long id; @Required public String label; // Define a taskForm static Form<Task> taskForm = form(Task.class); // search public static Finder<Long,Task> find = new Finder( Long.class, Task.class); // display tasks public static List<Task> all() { return find.all(); } // create new task public static Result newTask(Task newTask) { save(task); } // delete task public static void delete(Long id) { find.ref(id).delete(id); // find.ref(id).delete(); } }

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• How can one change the primary key using NHibernate.

  - by mark

  Dear ladies and sirs. I want to change the primary key of an entity in database, so that all the relevant foreign key constraints are updated as well./We are using NHibenate as our ORM. Is it possible to do it? Thanks. P.S. I know the practice of changing the primary key is highly discouraged. My problem is that my primary key is backed by a natural Id of the entity, which may sometimes change. We could, theoretically, utilize a unique primary key, unrelated to the natural key of the entity, but this complicates things too much in other places, so this is not an option.

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• What is the Fastest Java/PHP Bridge?

  - by The Rook

  A bi-directional communication is required between a Java application and a PHP web app. A Fast and low Resource consumption is the number 1 priority in this project There is the PHP/Java Brdige(PJB) project and there are benchmarks to show that is very fast. Do you know of a faster approach? xml over http strikes me as a bit wasteful, but I don't know of a better approach. Ideally this system would be a remote connection, but due to time constraints it might have to be local. Do you know of a fastest way to accomplish this bi-directional connection?

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• How can I fix Grails error: "No domain class found for name PrivacyOptions. Please try again and e

  - by ?????

  I'm just getting started with Groovy/Grails. I added a new domain controller to my project, and generate-controller doesn't like it. There are other indications something's wrong: If I run the app no table is actually created in the database for this. I've reduced the DomainController to one String field and no constraints, just to make sure there wasn't something wrong with my specification. I also tried renaming it, just in case there was something about the original name (Privacy) that conflicted with something. I'm sure I have the correct name, and that the file is called PrivacyOptions.groovy and inside the class is also called PrivacyOptions. Here's the error: Running script /opt/local/grails/scripts/GenerateController.groovy Environment set to development Domain class not found in grails-app/domain, trying hibernate mapped classes... No domain class found for name PrivacyOptions. Please try again and enter a valid domain class name

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• Truncating a table referenced by a foreign key

  - by born to hula

  Hey, We have two tables in a SQL Server 2005 database, A and B.There is a service which truncates table A every day. Recently, a foreign key constraint was added to table B, referencing table A. As a result, it isn't possible truncating table A anymore, even if table B is empty. Is there any workaround to get the same result as truncating table A? I've already tried the approach below but the identity wasn't reset. DBCC CHECKIDENT (TABLENAME, RESEED, 0) PS. before anyone points this as a duplicate, the different thing here is that I'm not allowed to drop constraints, nor creating any.

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• How to replace all the blanks within square brackets with an underscore using sed?

  - by Ringerrr

  I figured out that in order to turn [some name] into [some_name] I need to use the following expression: s/\(\[[^ ]*\) /\1_/ i.e. create a backreference capture for anything that starts with a literal '[' that contains any number of non space characters, followed by a space, to be replaced with the non space characters followed by an underscore. What I don't know yet though is how to alter this expression so it works for ALL underscores within the braces e.g. [a few words] into [a_few_words]. I sense that I'm close, but am just missing a chunk of knowledge that will unlock the key to making this thing work an infinite number of times within the constraints of the first set of []s contained in a line (of SQL Server DDL in this case). Any suggestions gratefully received....

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• Incorrect value for UNIQUE_CONSTRAINT_NAME in REFERENTIAL_CONSTRAINTS

  - by van

  I am listing all FK constraints for a given table using INFORMATION_SCHEMA set of views with the following query: SELECT X.UNIQUE_CONSTRAINT_NAME, "C".*, "X".* FROM "INFORMATION_SCHEMA"."KEY_COLUMN_USAGE" AS "C" INNER JOIN "INFORMATION_SCHEMA"."REFERENTIAL_CONSTRAINTS" AS "X" ON "C"."CONSTRAINT_NAME" = "X"."CONSTRAINT_NAME" AND "C"."TABLE_NAME" = 'MY_TABLE' AND "C"."TABLE_SCHEMA" = 'MY_SCHEMA' Everything works perfectly well, but for one particular constraint the value of UNIQUE_CONSTRAINT_NAME column is wrong, and I need it in order to find additional information from the referenced Column. Basically, for most of the rows the UNIQUE_CONSTRAINT_NAME contains the name of the unique constraint (or PK) in the referenced table, but for one particular FK it is the name of some other unique constraint. I dropped and re-created the FK - did not help. My assumption is that the meta-data is somehow screwed. Is there a way to rebuild the meta data so that the INFORMATION_SCHEMA views would actually show the correct data?

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• problems with Haskell's Number Types

  - by mindeavor.

  I have the following haskell code: fac n = product [1..n] taylor3s w0 f f' f'' t h = w1 : taylor3s w1 f f' f'' (t+h) h where hp i = h^i / fac i w1 = w0 + (hp 1) * f t w0 + (hp 2) * f' t w0 + (hp 3) * f'' t w0 taylor_results = take 4 $ taylor3s 1 f f' f'' 1 0.25 where f t x = t^4 - 4*x/t f' t x = 4*t^3 - 4*(f t x)/t + 4*x/t^2 f'' t x = 12*t^2 - 4*(f' t x)/t + 8*(f t x)/t^2 - 8*x/t^3 taylor_results is supposed to be a use case of taylor3s. However, there is something wrong with the number type inferencing. When I try to compile, this is the error I get: practice.hs:93:26: Ambiguous type variable `a' in the constraints: `Integral a' arising from a use of `taylor3s' at practice.hs:93:26-51 `Fractional a' arising from a use of `f' at practice.hs:93:37 Possible cause: the monomorphism restriction applied to the following: taylor_results :: [a] (bound at practice.hs:93:0) Probable fix: give these definition(s) an explicit type signature or use -XNoMonomorphismRestriction Can someone help me with understanding what the problem is?

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• Should I use a huge composite primary key or just a unique id?

  - by Jack

  I have been trying to do web scraping of a particular site and storing the results in a database. My original assumptions about the data allowed a schema where I could use fairly reasonable composite primary keys (usually containing only 2 or 3 fields) but as time went on, I realized that my original assumptions about the data were wrong and my primary keys were not as unique as I thought they were, so I have slowly been expanding them to contain more and more fields. In fact, I have recently come to believe that their database has no constraints whatsoever. Just today, I have finally expanded my a primary key for one of my tables to contain every field in that table and I thought now would be a good time to ask: is it better to add an auto-incrementing column that is just a unique id or just leave a composite primary key on the entire table?

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• Is it possible for a Grails Domain to have no 'id'?

  - by firnnauriel

  Is it possible to create a table that has no 'id'? For example, this is my domain: class SnbrActVector { int nid String term double weight static mapping = { version false id generator: 'identity' } static constraints = { } } When I run this SQL statement, it fails: insert into snbr_act_vector values (5, 'term', 0.5) I checked the table and 'id' is already set to autoincrement. I'm thinking that another option is to remove the 'id' itself. Or is there another workaround for this? Please assume that it is not an option to change the givent SQL statement.

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• What technologies to use for a particle system with enormous calculation demand?

  - by Amir Rezaei

  I have a particle system with X particles. Each particle tests for collision with other particles. This gives X*X = X^2 collision tests per frame. For 60f/s, this corresponds to 60*X^2 collision detection per second. What is the best technological approach for these intensive calculations? Should I use F#, C, C++ or C#, or something else? The following are constraints The code is written in C# with the latest XNA Multi-threaded may be considered No special algorithm that tests the collision with the nearest neighbors or that reduces the problem The last constraint may be strange, so let me explain. Regardless constraint 3, given a problem with enormous computational requirement what would be the best approach to solve the problem. An algorithm reduces the problem; still the same algorithm may behave different depending on technology. Consider pros and cons of CLR vs native C.

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• NHibernate SchemaUpdate adding existing foreign keys again?

  - by afsharm

  I'm using SchemaUpdate to synchronize my hbms with existing database. Database has recently created based on hbms and is completely up-to-date. But SchemaUpdate generates all foreign key constraints again. For example suppose you have Student and Teacher. Student has association to Teacher with name ArtTeacher. ArtTeacher is a foreign key from Student to Teacher. Suppose database is up-to-date and currently holde Student, Teacher and their foreign key relation. So HBM and Database are equivalent. Know SchemaUpdate must not do anything but when I see its generated scripts, it re-produce that foreign key again. Why this happens? Is there any way to avoid it?

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• Resizing uploaded images based on a maximum width in django (PIL)

  - by AndrewE

  I'm working on a simple message board app in Django that lets people upload images to be displayed in their posts. Since the div containing the posts is only 700px, I want to resize the uploaded images to a max width of something like 680px to save space rather than using css to display an image that's too large within the space constraints. I've been searching this site, google and the PIL docs for a while and haven't found any way of resizing an image on one dimension while maintaining the original aspect ratio. Given my inexperience, it's possible that I'm just not recognizing a solution that's plain to someone who knows what to look for.

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• Make a <div> square when there is a dynamically changing width based on percentage

  - by Nate

  I am working on a web app that will generate an NxN grid based on the user's selection of N. I want the total width of the grid to be relative (ie 100% of the available space) so that users can print on various paper sizes. I can easily calculate the width of the squares in the grid by % (ie: 100%/N), but I am having issues calculating the height. The height of a web page is always going to be infinite unless I artificially limit it which, like I said, I don't want to do. How can I make the squares in my grid be square versus rectangular when the height and width constraints of my grid are dynamic and not square? Thanks in advance!

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• Adding index key in Grails' Domain

  - by firnnauriel

  I tried following this reference and this is now my domain's code: class SnbrActVector { long nid String term double weight static mapping = { version false nid index:'Nid_Idx' } static constraints = { term(blank:false) } } What I want is to do is to add an index key for 'nid' column. I dropped the existing table and run the app again so the table is then recreated. However, when i check for list of indices, I can't see a 'Nid_Idx', only available is 'PRIMARY'. Do I have to manually create the index and name it 'Nid_idx in my mysql database? Thanks.

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• MySQL foreign key constraint disappearing

  - by Bramjam

  This is my table: /* oefenreeks leerplan */ CREATE TABLE leerplan_oefenreeks ( leerplan_oefenreeks_id INT PRIMARY KEY AUTO_INCREMENT NOT NULL, leerplan_id INT NOT NULL, oefenreeks_id INT NOT NULL, plaats INT NOT NULL ); /* fk */ ALTER TABLE leerplan_oefenreeks ADD CONSTRAINT fk_leerp_oefenr_leerplan FOREIGN KEY(leerplan_id) REFERENCES leerplan (leerplan_id) ON DELETE CASCADE; ALTER TABLE leerplan_oefenreeks ADD CONSTRAINT fk_leerp_oefenr_oefenreeks FOREIGN KEY(oefenreeks_id) REFERENCES oefenreeks (oefenreeks_id) ON DELETE CASCADE; /* when I execute the nexline, my fk_leerp_oefenr_leerplan constraint vanishes/disappears*/ ALTER TABLE leerplan_oefenreeks ADD CONSTRAINT un_leerp_oefenr UNIQUE(leerplan_id, oefenreeks_id); ALTER TABLE leerplan_oefenreeks ADD CONSTRAINT un_leerp_oefenr_plaats UNIQUE(leerplan_id, plaats); When I go and check only 3 constraints exist. fk_leerp_oefenr_leerplan disappears. I don't understand why this happens.

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• Syntax error in INSERT INTO statement in c# oledb?

  - by sameer

  I am having a table called SubMaster_Accounts, which contains 9 fields. In which I want to insert data to some fields and i want to store some other fields as NULL. I tried to write the query using query string, The sql query works perfectly when i insert the data for all the fields, but when i insert data as NULL to some of the fields it shows syntax error in Insert command. The fields which i want to insert as NULL are not constraints. How can i do it? This is my query string. insert into SubMaster_Account ([SMcode], [MSname], [Sname], [Openbalrs], [Openbalrs1], [Openbalmet], [Openbalmet1], [Creditdays], [Sdesc]) values ('" + SMcode + "','" + MSname + "','" + Sname + "'," + Openbalrs + ",'" + Openbalrs1 + "'," + Openbalmet + ",'" + Openbalmet1 + "'," + Creditdays + ",'" + Sdesc + "')

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• How can I treat a sequence value like a generated key?

  - by Jeff Knecht

  Here is my situation and my constraints: I am using Java 5, JDBC, and DB2 9.5 My database table contains a BIGINT value which represents the primary key. For various reasons that are too complicated to go into here, the way I insert records into the table is by executing an insert against a VIEW; an INSTEAD OF trigger retrieves the NEXT_VAL from a SEQUENCE and performs the INSERT into the target table. I can change the triggers, but I cannot change the underlying table or the general approach of inserting through the view. I want to retrieve the sequence value from JDBC as if it were a generated key. Question: How can I get access to the value pulled from the SEQUENCE. Is there some message I can fire within DB2 to float this sequence value back to the JDBC driver?

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