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• RESTful WCF Data Service Authentication

  - by Adrian Grigore

  Hi, I'd like to implement a REST api to an existing ASP.NET MVC website. I've managed to set up WCF Data services so that I can browse my data, but now the question is how to handle authentication. Right now the data service is secured via the site's built in forms authentication, and that's ok when accessing the service from AJAX forms. However, It's not ideal for a RESTful api. What I would like as an alternative to forms authentication is for the users to simply embed the user name and password into the url to the web service or as request parameters. For example, if my web service is usually accessible as http://localhost:1234/api.svc I'd like to be able to access it using the url http://localhost:1234/api.svc/{login}/{password} So, my questions are as follows: Is this a sane approach? If yes, how can I implement this? It seems trivial redirecting GET requests so that the login and password are attached as GET parameters. I also know how to inspect the http context and use those parameters to filter the results. But I am not sure if / how the same approach could be applied to POST, PUT and DELETE requests. Thanks, Adrian

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• asp.net Dynamic Data Site with own MetaData

  - by loviji

  Hello, I'm searching info about configuring own MetaData in asp.NET Dynamic Site. For example. I have a table in MS Sql Server with structure shown below: CREATE TABLE [dbo].[someTable]( [id] [int] NOT NULL, [pname] [nvarchar](20) NULL, [FullName] [nvarchar](50) NULL, [age] [int] NULL) and I there are 2 Ms Sql tables (I've created), sysTables and sysColumns. sysTables: ID sysTableName TableName TableDescription 1 | someTable |Persons |All Data about Persons in system sysColumns: ID TableName sysColumnName ColumnName ColumnDesc ColumnType MUnit 1 |someTable | sometable_pname| Name | Persona Name(ex. John)| nvarchar(20) | null 2 |someTable | sometable_Fullname| Full Name | Persona Name(ex. John Black)| nvarchar(50) | null 3 |someTable | sometable_age| age | Person age| int | null I want that, in Details/Edit/Insert/List/ListDetails pages use as MetaData sysColumns and sysTableData. Because, for ex. in DetailsPage fullName, it is not beatiful as Full Name . someIdea, is it possible? thanks Updated:: In List Page to display data from sysTables (metaData table) I've modified <h2 class="DDSubHeader"><%= tableName%></h2>. public string tableName; protected void Page_Init(object sender, EventArgs e) { table = DynamicDataRouteHandler.GetRequestMetaTable(Context); //added by me uqsikDataContext sd=new uqsikDataContext(); tableName = sd.sysTables.Where(n => n.sysTableName == table.DisplayName).FirstOrDefault().TableName; //end GridView1.SetMetaTable(table, table.GetColumnValuesFromRoute(Context)); GridDataSource.EntityTypeName = table.EntityType.AssemblyQualifiedName; if (table.EntityType != table.RootEntityType) { GridQueryExtender.Expressions.Add(new OfTypeExpression(table.EntityType)); } } so, what about sysColums? How can I get Data from my sysColumns table?

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• Jasper report exports empty data in PDF format when there is more data

  - by stanley

  I have a report to be exported in excel, pdf and word using jasper reports. I use xml file as the DataSource for the report, but when the data increases jasper report exports empty file in only for PDF format, when i reduce the data content it export the data available correctly. is there any limitation to pdf size? , how can we manage the size in jasper reports from java? My jrxml is really big, so i cannot add it here, i have added my java code which i use to export the content:- JRAbstractExporter exporter = null; if (format.equals("pdf")) { exporter = new JRPdfExporter(); jasperPrint.setPageWidth(Integer.parseInt( pWidth )); } else if (format.equals("xls")) { exporter = new JRXlsExporter(); } else if (format.equals("doc")) { jasperPrint.setPageWidth(Integer.parseInt( pWidth )); } exporter.setParameter(JRExporterParameter.JASPER_PRINT, jasperPrint); exporter.setParameter(JRExporterParameter.OUTPUT_STREAM, outputStream_); exporter.exportReport(); contents = outputStream_.toByteArray(); response.setContentType("application/"+format); response.addHeader("Content-disposition", "attachment;filename=" + name.toString() + "."+format);

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• Data loss when downloading data from LDAP server

  - by Ricky D'Amelio

  Hi there. This question comes from a previous one I asked about handling NSData objects: http://stackoverflow.com/questions/2453785/converting-nsdata-to-an-nsstring-representation-is-failing. I have reached the point where I am taking an NSImage, turning it into NSData and uploading those data bytes to the LDAP server. I am doing this like so; //connected successfully to LDAP server above... struct berval photo_berval; struct berval *jpegPhoto_values[2]; photo_berval.bv_len = [photo length]; photo_berval.bv_val = [photo bytes]; jpegPhoto_values[0] = &photo_berval; jpegPhoto_values[1] = NULL; mod.mod_type = "jpegPhoto"; mod.mod_op = LDAP_MOD_REPLACE|LDAP_MOD_BVALUES; mod.mod_bvalues = jpegPhoto_values; mods[0] = &mod; mods[1] = NULL; //perform the modify operation rc = ldap_modify_ext_s(ld, givenModifyEntry, mods, NULL, NULL); That happens with no errors, and you can see a big blob of data when you're in the command line. My problem is, when I go to access the same data at a later stage, I am getting an image file back that's about 120 times smaller than the original image. //find the jpegPhoto attribute photoA = ldap_first_attribute(ld, photoE, &photoBer); while (strcasecmp(photoA, "jpegphoto") != 0) { photoA = ldap_next_attribute(ld, photoE, photoBer); } //get the value of the attribute if ((list_of_photos = ldap_get_values_len(ld, photoE, photoA)) != NULL) { //get the first JPEG photo_data = *list_of_photos[0]; selectedPictureData = [NSData dataWithBytes:&photo_data length:sizeof(photo_data)]; [selectedPictureData writeToFile:@"/Users/username/Desktop/Photo 2.jpg" atomically:YES]; NSLog (@"%@", selectedPictureData); Has anyone successfully done this before or can anyone see what I might be doing wrong? I appreciate anyone's help. Sorry to post so many questions! Ricky.

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• Pros and cons of making database IDs consistent and "readable"

  - by gmale

  Question Is it a good rule of thumb for database IDs to be "meaningless?" Conversely, are there significant benefits from having IDs structured in a way where they can be recognized at a glance? What are the pros and cons? Background I just had a debate with my coworkers about the consistency of the IDs in our database. We have a data-driven application that leverages spring so that we rarely ever have to change code. That means, if there's a problem, a data change is usually the solution. My argument was that by making IDs consistent and readable, we save ourselves significant time and headaches, long term. Once the IDs are set, they don't have to change often and if done right, future changes won't be difficult. My coworkers position was that IDs should never matter. Encoding information into the ID violates DB design policies and keeping them orderly requires extra work that, "we don't have time for." I can't find anything online to support either position. So I'm turning to all the gurus here at SA! Example Imagine this simplified list of database records representing food in a grocery store, the first set represents data that has meaning encoded in the IDs, while the second does not: ID's with meaning: Type 1 Fruit 2 Veggie Product 101 Apple 102 Banana 103 Orange 201 Lettuce 202 Onion 203 Carrot Location 41 Aisle four top shelf 42 Aisle four bottom shelf 51 Aisle five top shelf 52 Aisle five bottom shelf ProductLocation 10141 Apple on aisle four top shelf 10241 Banana on aisle four top shelf //just by reading the ids, it's easy to recongnize that these are both Fruit on Aisle 4 ID's without meaning: Type 1 Fruit 2 Veggie Product 1 Apple 2 Banana 3 Orange 4 Lettuce 5 Onion 6 Carrot Location 1 Aisle four top shelf 2 Aisle four bottom shelf 3 Aisle five top shelf 4 Aisle five bottom shelf ProductLocation 1 Apple on aisle four top shelf 2 Banana on aisle four top shelf //given the IDs, it's harder to see that these are both fruit on aisle 4 Summary What are the pros and cons of keeping IDs readable and consistent? Which approach do you generally prefer and why? Is there an accepted industry best-practice?

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• Project setup for an ADO.NET/WCF DataService

  - by Slauma

  I'd like to implement a ADO.NET/WCF DataService and I am wondering what's the best way to setup a project in VS2008 SP1 for this purpose. Currently I have an ASP.NET web application project (not of "WebSite" project type). The data access layer is an Entity model (EF version 1) with SQL Server database. I have the Entity Model in a separate DLL project and the web application project references to this assembly for all data accesses. The ADO.NET/WCF DataService needs to communicate with the Entity model/database as well. It has to be hosted on the same web server (IIS 7.5) together with the web application. Since the DataService is not directly related to that specific web application (though it will provide and modify data from/in the same database the web application uses as well) my basic idea was to separate the DataService in its own new project (which also references the Entity Model DLL). Now I have seen that there is no project type "ADO.NET/WCF DataService" in VS2008 SP1. It seems only possible to add a DataService as an element to other existing projects, for instance Web Application projects. Why isn't there a separate DataService project type? Does this mean now that I have to add the DataService as an element to my Web Application project? Or shall I create a new Web Application project and add a DataService to it? (I could delete the pregenerated default.aspx since I do not need any web pages in this project.) What's the best way? Thank you for suggestions in advance!

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• Core Data 1-to-many relationship: List all related objects as section header in UITableView

  - by Snej

  Hi: I struggle with Core Data on the iPhone about the following: I have a 1-to-many relationship in Core Data. Assume the entities are called recipe and category. A category can have many recipes. I accomplished to get all recipes listed in a UITableView with section headers named after the category. What i want to achieve is to list all categories as section header, even those which have no recipe: category1 <--- this one should be displayed too category2 recipe_x recipe_y category3 recipe_z NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init]; NSEntityDescription *entity = [NSEntityDescription entityForName:@"Recipe" inManagedObjectContext:managedObjectContext]; [fetchRequest setEntity:entity]; [fetchRequest setFetchBatchSize:10]; NSSortDescriptor *sortDescriptor1 = [[NSSortDescriptor alloc] initWithKey:@"category.categoryName" ascending:YES]; NSSortDescriptor *sortDescriptor2 = [[NSSortDescriptor alloc] initWithKey:@"recipeName" ascending:YES]; NSArray *sortDescriptors = [[NSArray alloc] initWithObjects:sortDescriptor1,sortDescriptor2, nil]; [fetchRequest setSortDescriptors:sortDescriptors]; NSFetchedResultsController *aFetchedResultsController = [[NSFetchedResultsController alloc] initWithFetchRequest:fetchRequest managedObjectContext:managedObjectContext sectionNameKeyPath:@"category.categoryName" cacheName:@"Recipes"]; What is the most elegant way to achieve this with core data?

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• Designer serialization persistence problem in .NET, Windows Forms

  - by Jules

  ETA: I have a similar, smaller, problem here which, I suspect, is related to this problem. I have a class which has a readonly property that holds a collection of components (* not quite, see below). At design time, it's possible to select from the components on the design surface to add to the collection. (Think imagelist, but instead of selecting one, you can select as many as you want.) As a test, I inherit from button and attach my class to it as a property. The persistence problem occurs when I add a component,to the collection, from the design surface after I have added my button to the form. The best way to demonstrate this is to show you the designer generated code: Private Sub InitializeComponent() Dim Provider1 As WindowsApplication1.Provider = New WindowsApplication1.Provider Me.MyComponent2 = New WindowsApplication1.MyComponent Me.MyComponent1 = New WindowsApplication1.MyComponent Me.MyButton1 = New WindowsApplication1.MyButton Me.MyComponent3 = New WindowsApplication1.MyComponent Me.SuspendLayout() ' 'MyButton1 ' Me.MyButton1.ProviderCollection.Add(Me.MyButton1.InternalProvider) Me.MyButton1.ProviderCollection.Add(Me.MyComponent1.Provider) Me.MyButton1.ProviderCollection.Add(Me.MyComponent2.Provider) Me.MyButton1.ProviderCollection.Add(Provider1) //Wrong should be Me.MyComponent3.Provider ' 'Form1 ' Me.Controls.Add(Me.MyButton1) End Sub Friend WithEvents MyComponent1 As WindowsApplication1.MyComponent Friend WithEvents MyComponent2 As WindowsApplication1.MyComponent Friend WithEvents MyButton1 As WindowsApplication1.MyButton Friend WithEvents MyComponent3 As WindowsApplication1.MyComponent End Class As you can see from the code, the collection is not actually a collection of the components, but a collection of a property, 'Provider', from the components. It looks like the problem is occurring because MyComponent3 is created after MyButton. However, in my opinion, this should not make any difference - by the time the serializer comes to add the provider property of MyComponent3, it's already created. Note: You may wonder, why I'm not using AddRange to persist the collection. The reason for this is that if I do, the behaviour changes and none of the items will persist correctly. The designer will create local fields - like Provider1 - for each item in the collection. However if I add another collection to the class which holds the actual MyComponents and persist this, then, somehow, the AddRange method persists correctly in ProviderCollection! There seems to be some kind of quantum double slit experiment going down in code dom. How can I solve this problem?

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• Empty data problem - data layer or DAL?

  - by luckyluke

  I designing the new App now and giving the following question a lot of thought. I consume a lot of data from the warehouse, and the entities have a lot of dictionary based values (currency, country, tax-whatever data) - dimensions. I cannot be assured though that there won't be nulls. So I am thinking: create an empty value in each of teh dictionaries with special keyID - ie. -1 do the ETL (ssis) do the correct stuff and insert -1 where it needs to let the DAL know that -1 is special (Static const whatever thing) don't care in the code to check for nullness of dictionary entries because THEY will always have a value But maybe I should be thinking: import data AS IS let the DAL do the thinking using empty record Pattern still don't care in the code because business layer will have what it needs from DAL. I think is more of a approach thing but maybe i am missing something important here... What do You think? Am i clear? Please don't confuse it with empty record problem. I do use emptyCustomer think all the time and other defaults too.

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• Core Data - Entity Relationships Not Working as expected

  - by slimms

  I have set up my data model in xcode like so EntityA AttA1 AttA2 EntityB AttB1 AttB2 AttB3 I then set up the relationships EntityA Name: rlpToEntityB Destination: EntityB Inverse: rlpToEntityA To Many: Checked EntityB Name: rlpToEntityA Destination: EntityA Inverse: rlpToEntityB To Many: UnChecked i.e. relationship between the two where Each one of EntityA can have many EntityB's It is my understanding that if i fetch a subset of EntityB's I can then retrieve the values for the related EntityA's. I have this working so that i can retrieve the EntityB values using NSManagedObject *objMO = [fetchedResultsController objectAtIndexPath:indexPath]; strValueFromEntityB = [objMO valueForKey:@"AttB1"]; However, if I try to retrieve a related value from EntityA by doing the following strValueFromEntityA = [objMO valueForKey:@"AttA1"]; I get the error "The entity EntityB is not Key value coding-compliant for the key Atta1" Not surprisingly i suppose if i switch things around to fetch from EntityA i cannot access attributes of EntityB So it appears the defined relationshipare being ignored. Can anyone spot what i am doing wrong? I confess im very new to iPhone programming and especially to Core Data so please go easy on me and provide verbose explanations or point me in the direction a specific resource. I have downloaded the apple sample apps (Core Data Books, Top Songs and recipes) but I still can't work this out. Thanks in advance, Nev.

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• WCF Data Services - neither .Expand or .LoadProperty seems to do what I need

  - by TomK

  I am building a school management app where they track student tardiness and absences. I've got three entities to help me in this. A Students entity (first name, last name, ID, etc.); a SystemAbsenceTypes entity with SystemAbsenceTypeID values for Late, Absent-with-Reason, Absent-without-Reason; and a cross-reference table called StudentAbsences (matching the student IDs with the absence-type ID, plus a date, and a Notes field). What I want to do is query my entities for a given student, and then add up the number of each kind of Absence, for a given date range. I prepare my currentStudent object without a problem, then I do this... Me.Data.LoadProperty(currentStudent, "StudentAbsences") 'Loads the cross-ref data lblDaysLate.Text = (From ab In currentStudent.StudentAbsences Where ab.SystemAbsenceTypes.SystemAbsenceTypeID = Common.enuStudentAbsenceTypes.Late).Count.ToString ...and this second line fails, complaining it has no value for an object. I presume the problem is that while it DOES see that there are (let's say) four absences for the currentStudent (ie, currentStudent.StudentAbsences.Count = 4) -- it can't yet "peer into" each one of the absences to look at its type. How do I use .Expand or .LoadProperty to make this happen? I tried fiddling with .LoadProperty but it doesn't take a two-level syntax like so... Data.LoadProperty(currentStudent,"StudentAbsences.SystemAbsenceTypeID") or the like. Is there some other technique?

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• NSUndoManager with Core Data - Redo not working

  - by CJ

  I have a Core Data document-based app which support undo/redo via the built-in NSUndoManager associated with the NSManagedObjectContext. I have a few actions set up which perform numerous tasks within Core Data, wrap all these tasks into an undo group via beginUndoGrouping/endUndoGrouping, and are processed by the NSUndoManager. Undo works fine. I can perform several successive actions, and each then undo each one of them successively and my app's state is maintained correctly. However, the "Redo" menu item is never enabled. This means that the NSUndoManager is telling the menu that there are no items to redo. I am wondering why the NSUndoManager is seemingly forgetting about items once they are undone, and not allowing redos to occur? One thing I should mention is that I'm disabling undo registration after a document is opened/created. When I perform an action, I call enableUndoRegistration, beginUndoGrouping, perform the action, then call processPendingChanges, setActionName:, endUndoGrouping, and finally disableUndoRegistration. This makes sure that only specific actions are undoable, and any other data changes I make outside of these go unnoticed to the NSUndoManager. This may be a part of the issue, but if so I'm wondering why it's affecting redo? Thanks in advance.

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• Regressing panel data in SAS.

  - by John

  Hey Guys, thanks to your help I succesfully managed all my databases! I am now looking at a panel data set on which I have to regress. Since I only started my Phd this semester together with the econometrics courses I am still new to many statistic applications and regression methods. I want to do a simple regression as in Y = x1 x2 x3 etc, now I already browsed through some literature and found that for panel data it's common to do a fixed effects regression. Also, my Y variable only has positive values so I was thinking in the direction of a Tobit model? I'm doing some research concerning the coverage of analysts in the financial business. My independent variable is the coverage of analysts on a certain firm, so per observation i have 1 analyst and 1 firm, together with different characteristics(market cap and betas etc) of the firm. All this data is monthly. As coverage cannot become negative (only 0) I was thinking of a Tobit model? Do you guys have any ideas what would be a good regression method? Or have some good sources (e books, written books, through university I have access to almost anything concerning my field of work) of information (cause I do have to learn these things for future research)? Thanks!

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• Creating LINQ to SQL Data Models' Data Contexts with ASP.NET MVC

  - by Maxim Z.

  I'm just getting started with ASP.NET MVC, mostly by reading ScottGu's tutorial. To create my database connections, I followed the steps he outlined, which were to create a LINQ-to-SQL dbml model, add in the database tables through the Server Explorer, and finally to create a DataContext class. That last part is the part I'm stuck on. In this class, I'm trying to create methods that work around the exposed data. Following the example in the tutorial, I created this: using System; using System.Collections.Generic; using System.Linq; using System.Web; namespace MySite.Models { public partial class MyDataContext { public List<Post> GetPosts() { return Posts.ToList(); } public Post GetPostById(int id) { return Posts.Single(p => p.ID == id); } } } As you can see, I'm trying to use my Post data table. However, it doesn't recognize the "Posts" part of my code. What am I doing wrong? I have a feeling that my problem is related to my not adding the data tables correctly, but I'm not sure. Thanks in advance.

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• Storing high precision latitude/longitude numbers in iOS Core Data

  - by Bryan

  I'm trying to store Latitude/Longitudes in core data. These end up being anywhere from 6-20 digit precision. And for whatever reason, i had them as floats in Core Data, its rounding them and not giving me the exact values back. I tried "decimal" type, with no luck either. Are NSStrings my only other option? EDIT NSManagedObject: @interface Event : NSManagedObject { } @property (nonatomic, retain) NSDecimalNumber * dec; @property (nonatomic, retain) NSDate * timeStamp; @property (nonatomic, retain) NSNumber * flo; @property (nonatomic, retain) NSNumber * doub; Here's the code for a sample number that I store into core data: NSNumber *n = [NSDecimalNumber decimalNumberWithString:@"-97.12345678901234567890123456789"]; Code to access it again: NSNumber *n = [managedObject valueForKey:@"dec"]; NSNumber *f = [managedObject valueForKey:@"flo"]; NSNumber *d = [managedObject valueForKey:@"doub"]; Printed values: Printing description of n: -97.1234567890124 Printing description of f: <CFNumber 0x603f250 [0xfef3e0]>{value = -97.12345678901235146441, type = kCFNumberFloat64Type} Printing description of d: <CFNumber 0x6040310 [0xfef3e0]>{value = -97.12345678901235146441, type = kCFNumberFloat64Type}

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• Pass a data.frame column name to a function

  - by Kevin Middleton

  I'm trying to write a function to accept a data.frame (x) and a column from it. The function performs some calculations on x and later returns another data.frame. I'm stuck on the best-practices method to pass the column name to the function. The two minimal examples fun1 and fun2 below produce the desired result, being able to perform operations on x$column, using max() as an example. However, both rely on the seemingly (at least to me) inelegant (1) call to substitute() and possibly eval() and (2) the need to pass the column name as a character vector. fun1 <- function(x, column){ do.call("max", list(substitute(x[a], list(a = column)))) } fun2 <- function(x, column){ max(eval((substitute(x[a], list(a = column))))) } df <- data.frame(A = 1:20, B = rnorm(10)) fun1(df, "B") fun2(df, "B") I would like to be able to call the function as fun(df, B), for example. Other options I have considered but have not tried: Pass column as an integer of the column number. I think this would avoid substitute(). Ideally, the function could accept either. with(x, get(column)), but, even if it works, I think this would still require substitute Make use of formula() and match.call(), neither of which I have much experience with. Subquestion: Is do.call() preferred over eval()? Thanks, Kevin

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• LOAD DATA INFILE with variables

  - by Hasitha

  I was tring to use the LOAD DATA INFILE as a sotred procedure but it seems it cannot be done. Then i tried the usual way of embedding the code to the application itself like so, conn = new MySqlConnection(connStr); conn.Open(); MySqlCommand cmd = new MySqlCommand(); cmd = conn.CreateCommand(); string tableName = getTableName(serverName); string query = "LOAD DATA INFILE '" + fileName + "'INTO TABLE "+ tableName +" FIELDS TERMINATED BY '"+colSep+"' ENCLOSED BY '"+colEncap+"' ESCAPED BY '"+colEncap+"'LINES TERMINATED BY '"+colNewLine+"' ("+colUpFormat+");"; cmd.CommandText = query; cmd.ExecuteNonQuery(); conn.Close(); The generated query that gets saved in the string variable query is, LOAD DATA INFILE 'data_file.csv'INTO TABLE tbl_shadowserver_bot_geo FIELDS TERMINATED BY ',' ENCLOSED BY '"' ESCAPED BY '"'LINES TERMINATED BY '\n' (timestamp,ip,port,asn,@dummy,@dummy,@dummy,@dummy,@dummy,@dummy,url,agent,@dummy,@dummy,@dummy,@dummy,@dummy,@dummy,@dummy,@dummy,@dummy,@dummy,@dummy); But now when i run the program it gives an error saying, MySQLException(0x80004005) Parameter @dummy must be defined first. I dont know how to get around this, but when i use the same query on mysql itself directly it works fine. PLEASE help me..thank you very much :)

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• Using Constraints on Hierarchical Data in a Self-Referential Table

  - by pbarney

  Suppose you have the following table, intended to represent hierarchical data: +--------+-------------+ | Field | Type | +--------+-------------+ | id | int(10) | | parent | int(10) | | name | varchar(45) | +--------+-------------+ The table is self-referential in that the parent_id refers to id. So you might have the following data: +----+--------+---------------+ | id | parent | name | +----+--------+---------------+ | 1 | 0 | fruit | | 2 | 0 | vegetable | | 3 | 1 | apple | | 4 | 1 | orange | | 5 | 3 | red delicious | | 6 | 3 | granny smith | | 7 | 3 | gala | +----+--------+---------------+ Using MySQL, I am trying to impose a (self-referential) foreign key constraint upon the data to update on cascades and prevent deletion of fruit if they have "children." So I used the following: CREATE TABLE `idtlp_main`.`fruit` ( `id` INT(10) UNSIGNED NOT NULL AUTO_INCREMENT, `parent` INT(10) UNSIGNED, `name` VARCHAR(45) NOT NULL, PRIMARY KEY (`id`), CONSTRAINT `fk_parent` FOREIGN KEY (`parent`) REFERENCES `fruit` (`id`) ON UPDATE CASCADE ON DELETE RESTRICT ) ENGINE = InnoDB; From what I understand, this should fit my requirements. (And parent must default to null to allow insertions, correct?) The problem is, if I change the id of a record, it will not cascade: Cannot delete or update a parent row: a foreign key constraint fails (`iddoc_main`.`fruit`, CONSTRAINT `fk_parent` FOREIGN KEY (`parent`) REFERENCES `fruit` (`id`) ON UPDATE CASCADE) What am I missing? Feel free to correct me if my terminology is screwed up... I'm new to constraints.

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• iPhone application update (using Core Data on Sqlite)

  - by owen

  I have an app which is using Core Data on Sqlite, Now I have a update which has some DB structure changes say adding a new table I know when an app get updated, it updates the app binary only, nothing on document directory will be changed. When the app gets updated and launchs at the first time and run [[NSPersistentStoreCoordinator alloc] initWithManagedObjectModel:[self managedObjectModel]]; It will find the difference between the data model and DB structure in Sqlite and will throw an exception and quit. Error: "The model used to open the store is incompatible with the one used to create the store" So, can anyone here give me some idea how to update an app when there is a DB structure change? I think we can run a DB script to create that new table when it launchs the update at the first time. But if there are other changes like changing the type of some fields or deleting some fields, and we need to migrate the old data, this is really a headache. In this case, Is the only way to do is creating a new app? Is there anyone tried something similar like this?

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• EC2 persistence of machine

  - by Seagull

  I want to 'persist' my Amazon EC2 images. My scenario: I have a range of Windows and Linux machines Some machines are EBS backed, whereas others are S3 backed. I need to be able to persist a machine (put it to sleep), preferably keeping all settings active I had them when the machine was running. I need to be able to quickly wake up a machine from sleep [Ideally with an SLA of less than 2 min to turn-on, if such an SLA is available with Amazon]. Here's the stuff that confuses me: AWS allows me to put EBS backed machines to sleep, but not S3 backed. I believe I can put S3 machines into some sort of persistence mode. But this involves shutting down the machine, writing it to S3 storage and then recovering from there (not a real sleep mode, but at least I don't continue to get billed for CPU). S3 backing seems to take a long time to either writing a machine to disk, or to recover (turn on a machine). I can't tell immediately which machines are EBS backed and which are S3 backed? It seems like I can instantiate either type, but it's not immediately clear how Amazon decided whether a given machine should be EBS or S3 backed. Advice?

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• Point data structure for a sketching application

  - by bebraw

  I am currently developing a little sketching application based on HTML5 Canvas element. There is one particular problem I haven't yet managed to find a proper solution for. The idea is that the user will be able to manipulate existing stroke data (points) quite freely. This includes pushing point data around (ie. magnet tool) and manipulating it at whim otherwise (ie. altering color). Note that the current brush engine is able to shade by taking existing stroke data in count. It's a quick and dirty solution as it just iterates the points in the current stroke and checks them against a distance rule. Now the problem is how to do this in a nice manner. It is extremely important to be able to perform efficient queries that return all points within given canvas coordinate and radius. Other features, such as space usage, should be secondary to this. I don't mind doing some extra processing between strokes while the user is not painting. Any pointers are welcome. :)

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• Algorithm detect repeating/similiar strings in a corpus of data -- say email subjects, in Python

  - by RizwanK

  I'm downloading a long list of my email subject lines , with the intent of finding email lists that I was a member of years ago, and would want to purge them from my Gmail account (which is getting pretty slow.) I'm specifically thinking of newsletters that often come from the same address, and repeat the product/service/group's name in the subject. I'm aware that I could search/sort by the common occurrence of items from a particular email address (and I intend to), but I'd like to correlate that data with repeating subject lines.... Now, many subject lines would fail a string match, but "Google Friends : Our latest news" "Google Friends : What we're doing today" are more similar to each other than a random subject line, as is: "Virgin Airlines has a great sale today" "Take a flight with Virgin Airlines" So -- how can I start to automagically extract trends/examples of strings that may be more similar. Approaches I've considered and discarded ('because there must be some better way'): Extracting all the possible substrings and ordering them by how often they show up, and manually selecting relevant ones Stripping off the first word or two and then count the occurrence of each sub string Comparing Levenshtein distance between entries Some sort of string similarity index ... Most of these were rejected for massive inefficiency or likelyhood of a vast amount of manual intervention required. I guess I need some sort of fuzzy string matching..? In the end, I can think of kludgy ways of doing this, but I'm looking for something more generic so I've added to my set of tools rather than special casing for this data set. After this, I'd be matching the occurring of particular subject strings with 'From' addresses - I'm not sure if there's a good way of building a data structure that represents how likely/not two messages are part of the 'same email list' or by filtering all my email subjects/from addresses into pools of likely 'related' emails and not -- but that's a problem to solve after this one. Any guidance would be appreciated.

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• What changes in Core Data after a save?

  - by Splash6

  I have a Core Data based mac application that is working perfectly well until I save a file. When I save a file it seems like something changes in core data because my original fetch request no longer fetches anything. This is the fetch request that works before saving but returns an empty array after saving. NSEntityDescription *outputCellEntityDescription = [NSEntityDescription entityForName:@"OutputCell" inManagedObjectContext:[[self document] managedObjectContext]]; NSFetchRequest *outputCellRequest = [[[NSFetchRequest alloc] init] autorelease]; [outputCellRequest setEntity:outputCellEntityDescription]; NSPredicate *outputCellPredicate = [NSPredicate predicateWithFormat:@"(cellTitle = %@)", outputCellTitle]; [outputCellRequest setPredicate:outputCellPredicate]; NSError *outputCellError = nil; NSArray *outputCellArray = [[[self document] managedObjectContext] executeFetchRequest:outputCellRequest error:&outputCellError]; I have checked with [[[self document] managedObjectContext] registeredObjects] to see that the object still exists after the save and nothing seems to have changed and the object still exists. It is probably something fairly basic but does anyone know what I might be doing wrong? If not can anyone give me any pointers to what might be different in the Core Data model after a save so I might have some clues why the fetch request stops working after saving?

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• C++: best way to implement globally scoped data

  - by bobobobo

  I'd like to make program-wide data in a C++ program, without running into pesky LNK2005 errors when all the source files #includes this "global variable repository" file. I have 2 ways to do it in C++, and I'm asking which way is better. The easiest way to do it in C# is just public static members. C#: public static class DataContainer { public static Object data1 ; public static Object data2 ; } In C++ you can do the same thing C++ global data way#1: class DataContainer { public: static Object data1 ; static Object data2 ; } ; Object DataContainer::data1 ; Object DataContainer::data2 ; However there's also extern C++ global data way #2: class DataContainer { public: Object data1 ; Object data2 ; } ; extern DataContainer * dataContainer ; // instantiate in .cpp file In C++ which is better, or possibly another way which I haven't thought about? The solution has to not cause LNK2005 "object already defined" errors.

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• Understanding Hibernate saveOrUpdate and the Persistence Life Cycle

  - by Stephano

  The books that I've read regarding hibernate are, at best, reference tomes. They very seldom have good code examples, so I tend to use online resources for those needs. However, I've always had a problem understanding the basic idea of hibernate persistence. I've read the books and understand the concepts, but in practice, I often see results that I don't understand. Perhaps you all can help, as you have in the past. Let's look at a simple example of a dog and a cat that are friends. This isn't a rare occurrence. It also has the benefit of being much more interesting than my business case. We want a function called "saveFriends" that takes a dog name and a cat name. We'll save the Dog and then the Cat. For this example to work, the cat is going to have a reference back to the dog. I understand this isn't an ideal example, but it's cute and works for our purposes. FriendService.java public int saveFriends(String dogName, String catName) { Dog fido = new Dog(); Cat felix = new Cat(); fido.name = dogName; fido = animalDao.saveDog(fido); felix.name = catName; [ex.A]felix.friend = fido; [ex.B]felix.friend = animalDao.getDogByName(dogName); animalDao.saveCat(felix); } AnimalDao.java (extends HibernateDaoSupport) public Dog saveDog(Dog dog) { getHibernateTemplate().saveOrUpdate(dog); return dog } public Cat saveCat(Cat cat) { getHibernateTemplate().saveOrUpdate(cat); return cat; } public Dog getDogByName(String name) { return (Dog) getHibernateTemplate().find("from Dog where name=?", name).get(0); } Now, assume for a minute that I would like to use either example A or example B to save my friend. Is one better than the other to use? I'll understand if neither of those examples work, but please explain why.

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