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  • Explained: EF 6 and “Could not determine storage version; a valid storage connection or a version hint is required.”

    - by Ken Cox [MVP]
    I have a legacy ASP.NET 3.5 web site that I’ve upgraded to a .NET 4 web application. At the same time, I upgraded to Entity Framework 6. Suddenly one of the pages returned the following error: [ArgumentException: Could not determine storage version; a valid storage connection or a version hint is required.]    System.Data.SqlClient.SqlVersionUtils.GetSqlVersion(String versionHint) +11372412    System.Data.SqlClient.SqlProviderServices.GetDbProviderManifest(String versionHint) +91    System.Data.Common.DbProviderServices.GetProviderManifest(String manifestToken) +92 [ProviderIncompatibleException: The provider did not return a ProviderManifest instance.]    System.Data.Common.DbProviderServices.GetProviderManifest(String manifestToken) +11431433    System.Data.Metadata.Edm.Loader.InitializeProviderManifest(Action`3 addError) +11370982    System.Data.EntityModel.SchemaObjectModel.Schema.HandleAttribute(XmlReader reader) +216 A search of the error message didn’t turn up anything helpful except that someone mentioned that the error messages was bogus in his case. The page in question uses the ASP.NET EntityDataSource control, consumed by a Telerik RadGrid. This is a fabulous combination for putting a huge amount of functionality on a page in a very short time. Unfortunately, the 6.0.1 release of EF6 doesn’t support EntityDataSource. According to the people in charge, support is planned but there’s no timeline for an EntityDataSource build that works with EF6.  I’m not sure what to do in the meantime. Should I back out EF6 or manually wire up the RadGrid? The upshot is that you might want to rethink plans to upgrade to Entity Framework 6 for Web forms projects if they rely on that handy control. It might also help to spend a User voice vote here:  http://data.uservoice.com/forums/72025-entity-framework-feature-suggestions/suggestions/3702890-support-for-asp-net-entitydatasource-and-dynamicda

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  • Announcing Entity Framework Code-First (CTP5 release)

    - by ScottGu
    This week the data team released the CTP5 build of the new Entity Framework Code-First library.  EF Code-First enables a pretty sweet code-centric development workflow for working with data.  It enables you to: Develop without ever having to open a designer or define an XML mapping file Define model objects by simply writing “plain old classes” with no base classes required Use a “convention over configuration” approach that enables database persistence without explicitly configuring anything Optionally override the convention-based persistence and use a fluent code API to fully customize the persistence mapping I’m a big fan of the EF Code-First approach, and wrote several blog posts about it this summer: Code-First Development with Entity Framework 4 (July 16th) EF Code-First: Custom Database Schema Mapping (July 23rd) Using EF Code-First with an Existing Database (August 3rd) Today’s new CTP5 release delivers several nice improvements over the CTP4 build, and will be the last preview build of Code First before the final release of it.  We will ship the final EF Code First release in the first quarter of next year (Q1 of 2011).  It works with all .NET application types (including both ASP.NET Web Forms and ASP.NET MVC projects). Installing EF Code First You can install and use EF Code First CTP5 using one of two ways: Approach 1) By downloading and running a setup program.  Once installed you can reference the EntityFramework.dll assembly it provides within your projects.      or: Approach 2) By using the NuGet Package Manager within Visual Studio to download and install EF Code First within a project.  To do this, simply bring up the NuGet Package Manager Console within Visual Studio (View->Other Windows->Package Manager Console) and type “Install-Package EFCodeFirst”: Typing “Install-Package EFCodeFirst” within the Package Manager Console will cause NuGet to download the EF Code First package, and add it to your current project: Doing this will automatically add a reference to the EntityFramework.dll assembly to your project:   NuGet enables you to have EF Code First setup and ready to use within seconds.  When the final release of EF Code First ships you’ll also be able to just type “Update-Package EFCodeFirst” to update your existing projects to use the final release. EF Code First Assembly and Namespace The CTP5 release of EF Code First has an updated assembly name, and new .NET namespace: Assembly Name: EntityFramework.dll Namespace: System.Data.Entity These names match what we plan to use for the final release of the library. Nice New CTP5 Improvements The new CTP5 release of EF Code First contains a bunch of nice improvements and refinements. Some of the highlights include: Better support for Existing Databases Built-in Model-Level Validation and DataAnnotation Support Fluent API Improvements Pluggable Conventions Support New Change Tracking API Improved Concurrency Conflict Resolution Raw SQL Query/Command Support The rest of this blog post contains some more details about a few of the above changes. Better Support for Existing Databases EF Code First makes it really easy to create model layers that work against existing databases.  CTP5 includes some refinements that further streamline the developer workflow for this scenario. Below are the steps to use EF Code First to create a model layer for the Northwind sample database: Step 1: Create Model Classes and a DbContext class Below is all of the code necessary to implement a simple model layer using EF Code First that goes against the Northwind database: EF Code First enables you to use “POCO” – Plain Old CLR Objects – to represent entities within a database.  This means that you do not need to derive model classes from a base class, nor implement any interfaces or data persistence attributes on them.  This enables the model classes to be kept clean, easily testable, and “persistence ignorant”.  The Product and Category classes above are examples of POCO model classes. EF Code First enables you to easily connect your POCO model classes to a database by creating a “DbContext” class that exposes public properties that map to the tables within a database.  The Northwind class above illustrates how this can be done.  It is mapping our Product and Category classes to the “Products” and “Categories” tables within the database.  The properties within the Product and Category classes in turn map to the columns within the Products and Categories tables – and each instance of a Product/Category object maps to a row within the tables. The above code is all of the code required to create our model and data access layer!  Previous CTPs of EF Code First required an additional step to work against existing databases (a call to Database.Initializer<Northwind>(null) to tell EF Code First to not create the database) – this step is no longer required with the CTP5 release.  Step 2: Configure the Database Connection String We’ve written all of the code we need to write to define our model layer.  Our last step before we use it will be to setup a connection-string that connects it with our database.  To do this we’ll add a “Northwind” connection-string to our web.config file (or App.Config for client apps) like so:   <connectionStrings>          <add name="Northwind"          connectionString="data source=.\SQLEXPRESS;Integrated Security=SSPI;AttachDBFilename=|DataDirectory|\northwind.mdf;User Instance=true"          providerName="System.Data.SqlClient" />   </connectionStrings> EF “code first” uses a convention where DbContext classes by default look for a connection-string that has the same name as the context class.  Because our DbContext class is called “Northwind” it by default looks for a “Northwind” connection-string to use.  Above our Northwind connection-string is configured to use a local SQL Express database (stored within the \App_Data directory of our project).  You can alternatively point it at a remote SQL Server. Step 3: Using our Northwind Model Layer We can now easily query and update our database using the strongly-typed model layer we just built with EF Code First. The code example below demonstrates how to use LINQ to query for products within a specific product category.  This query returns back a sequence of strongly-typed Product objects that match the search criteria: The code example below demonstrates how we can retrieve a specific Product object, update two of its properties, and then save the changes back to the database: EF Code First handles all of the change-tracking and data persistence work for us, and allows us to focus on our application and business logic as opposed to having to worry about data access plumbing. Built-in Model Validation EF Code First allows you to use any validation approach you want when implementing business rules with your model layer.  This enables a great deal of flexibility and power. Starting with this week’s CTP5 release, EF Code First also now includes built-in support for both the DataAnnotation and IValidatorObject validation support built-into .NET 4.  This enables you to easily implement validation rules on your models, and have these rules automatically be enforced by EF Code First whenever you save your model layer.  It provides a very convenient “out of the box” way to enable validation within your applications. Applying DataAnnotations to our Northwind Model The code example below demonstrates how we could add some declarative validation rules to two of the properties of our “Product” model: We are using the [Required] and [Range] attributes above.  These validation attributes live within the System.ComponentModel.DataAnnotations namespace that is built-into .NET 4, and can be used independently of EF.  The error messages specified on them can either be explicitly defined (like above) – or retrieved from resource files (which makes localizing applications easy). Validation Enforcement on SaveChanges() EF Code-First (starting with CTP5) now automatically applies and enforces DataAnnotation rules when a model object is updated or saved.  You do not need to write any code to enforce this – this support is now enabled by default.  This new support means that the below code – which violates our above rules – will automatically throw an exception when we call the “SaveChanges()” method on our Northwind DbContext: The DbEntityValidationException that is raised when the SaveChanges() method is invoked contains a “EntityValidationErrors” property that you can use to retrieve the list of all validation errors that occurred when the model was trying to save.  This enables you to easily guide the user on how to fix them.  Note that EF Code-First will abort the entire transaction of changes if a validation rule is violated – ensuring that our database is always kept in a valid, consistent state. EF Code First’s validation enforcement works both for the built-in .NET DataAnnotation attributes (like Required, Range, RegularExpression, StringLength, etc), as well as for any custom validation rule you create by sub-classing the System.ComponentModel.DataAnnotations.ValidationAttribute base class. UI Validation Support A lot of our UI frameworks in .NET also provide support for DataAnnotation-based validation rules. For example, ASP.NET MVC, ASP.NET Dynamic Data, and Silverlight (via WCF RIA Services) all provide support for displaying client-side validation UI that honor the DataAnnotation rules applied to model objects. The screen-shot below demonstrates how using the default “Add-View” scaffold template within an ASP.NET MVC 3 application will cause appropriate validation error messages to be displayed if appropriate values are not provided: ASP.NET MVC 3 supports both client-side and server-side enforcement of these validation rules.  The error messages displayed are automatically picked up from the declarative validation attributes – eliminating the need for you to write any custom code to display them. Keeping things DRY The “DRY Principle” stands for “Do Not Repeat Yourself”, and is a best practice that recommends that you avoid duplicating logic/configuration/code in multiple places across your application, and instead specify it only once and have it apply everywhere. EF Code First CTP5 now enables you to apply declarative DataAnnotation validations on your model classes (and specify them only once) and then have the validation logic be enforced (and corresponding error messages displayed) across all applications scenarios – including within controllers, views, client-side scripts, and for any custom code that updates and manipulates model classes. This makes it much easier to build good applications with clean code, and to build applications that can rapidly iterate and evolve. Other EF Code First Improvements New to CTP5 EF Code First CTP5 includes a bunch of other improvements as well.  Below are a few short descriptions of some of them: Fluent API Improvements EF Code First allows you to override an “OnModelCreating()” method on the DbContext class to further refine/override the schema mapping rules used to map model classes to underlying database schema.  CTP5 includes some refinements to the ModelBuilder class that is passed to this method which can make defining mapping rules cleaner and more concise.  The ADO.NET Team blogged some samples of how to do this here. Pluggable Conventions Support EF Code First CTP5 provides new support that allows you to override the “default conventions” that EF Code First honors, and optionally replace them with your own set of conventions. New Change Tracking API EF Code First CTP5 exposes a new set of change tracking information that enables you to access Original, Current & Stored values, and State (e.g. Added, Unchanged, Modified, Deleted).  This support is useful in a variety of scenarios. Improved Concurrency Conflict Resolution EF Code First CTP5 provides better exception messages that allow access to the affected object instance and the ability to resolve conflicts using current, original and database values.  Raw SQL Query/Command Support EF Code First CTP5 now allows raw SQL queries and commands (including SPROCs) to be executed via the SqlQuery and SqlCommand methods exposed off of the DbContext.Database property.  The results of these method calls can be materialized into object instances that can be optionally change-tracked by the DbContext.  This is useful for a variety of advanced scenarios. Full Data Annotations Support EF Code First CTP5 now supports all standard DataAnnotations within .NET, and can use them both to perform validation as well as to automatically create the appropriate database schema when EF Code First is used in a database creation scenario.  Summary EF Code First provides an elegant and powerful way to work with data.  I really like it because it is extremely clean and supports best practices, while also enabling solutions to be implemented very, very rapidly.  The code-only approach of the library means that model layers end up being flexible and easy to customize. This week’s CTP5 release further refines EF Code First and helps ensure that it will be really sweet when it ships early next year.  I recommend using NuGet to install and give it a try today.  I think you’ll be pleasantly surprised by how awesome it is. Hope this helps, Scott

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  • PHP frameworks - should I use them?

    - by 30secondstosam
    First of all let me explain who I am: I am a PHP Developer working for a company developing their CMS which handles online stores, data feeds and other content like blogs. I have been programming for 6 years and 4 of those have been in PHP. (I used to be a C# developer). My question is regarding PHP frameworks. I see so many jobs asking for zend, cakephp and other MVC types of frameworks. However, even as an experienced developer I have never used a PHP framework. Should I start learning? If so where do I even start as there are so many. I am about to re-write so much of my work's CMS and I'm wondering whether I could help myself a lot by using a framework. What do people think? Considering I will be re-writing a lot of the online store stuff... I am experienced in OO and I have used the .NET framework in the past. Thanks in advance for the replies.

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  • Architecture : am I doing things right?

    - by Jeremy D
    I'm trying to use a '~classic' layered arch using .NET and Entity Framework. We are starting from a legacy database which is a little bit crappy: Inconsistent naming Unneeded views (view referencing other views, select * views etc...) Aggregated columns Potatoes and Carrots in the same table etc... So I ended with fully isolating my database structure from my domain model. To do so EF entities are hidden from presentation layer. The goal is to permit an easier database refactoring while lowering the impact of it on applications. I'm now facing a lot of challenges and I'm starting to ask myself if I'm doing things right. My Domain Model is highly volatile, it keeps evolving with apps as new fields needs are arising. Complexity of it keeps raising and class it contains start to get a lot of properties. Creating include strategy and reprojecting to EF is very tricky (my domain objects don't have any kind of lazy/eager loading relationship properties): DomainInclude<Domain.Model.Bar>.Include("Customers").Include("Customers.Friends") // To... IFooContext.Bars.Include(...).Include(...).Where(...) Some framework are raping the isolation levels (Devexpress Grids which needs either XPO or IQueryable for filtering and paging large data sets) I'm starting to ask myself if : the isolation of EF auto-generated entities is an unneeded cost. I should allow frameworks to hit IQueryable? Slow slope to hell? (it's really hard to isolate DevExpress framework, any successful experience?) the high volatility of my domain model is normal? Did you have similar difficulties? Any advice based on experience?

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  • Where should "display functions" live in an MVC web app?

    - by User
    I'm using the Yii Framework which is an MVC php framework that is pretty similar to your standard web-based MVC framework. I want to display the related data from a many-to-many table as a list of strings in my view. Assuming a table schema like: tag { id, name } post { id, title, content, date } post_tag { post_id, tag_id } A post will display like: Date: 9/27/2012 Title: Some Title Content: blah blah blah... Tags: Smart Funny Cool Informative I can achieve this by doing something like this in my Post view: <?php echo join(' ', array_map(function($tag) { return $tag->name; }, $model->tags)); ?> (where $model->tags is an array of Tag objects associated with my model) My questions are: Is this amount of code/logic okay in the view? (Personally I think I'd rather just reference a property or call a single function.) If not, where should this code live? In the model? the controller? a helper? Potentially I may want to use in in other views as well. Ultimately I think its purely a display issue which would make me think it should be in the view, but then I have to repeat the code in any view I want to use it in.

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  • What's wrong performing unit test against concrete implementation if your frameworks are not going to change?

    - by palm snow
    First a bit of background: We are re-architecting our product suite that was written 10 years ago and served its purpose. One thing that we cannot change is the database schema as we have 500+ client base using this system. Our db schema has over 150+ tables. We have decided on using Entity Framework 4.1 as DAL and still evaluating various frameworks for storing our business logic. I am investigation to bring unit testing into the mix but I also confused as to how far I need to go with setting up a full blown TDD environment. One aspect of setting up unit testing is by getting into implementing Repository, unit of work and mocking frameworks etc. This mean there will be cost and investment on the code-bloat associated with all these frameworks. I understand some of this could be auto-generated but when it comes to things like behaviors, that will be mostly hand written. Just to be clear, I am not questioning the important of unit testing your code. I am just not sure we need all its components (like repository, mocking etc.) when we are fairly certain of storage mechanism/framework (SQL Server/Entity Framework). All that code bloat with generic repositories make sense when you need a generic layers with ability to change this whenever you like however its very likely a YAGNI in our case. What we need is more of integration testing where we can unit-test our code with concrete repository objects and test data in database. In this scenario, just running integration test seem to be more beneficial in our case. Any thoughts if I am missing any thing here?

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  • Caching no .NET Framework 4.0

    - by anobre
    Olá pessoal, como estão? Hoje vou apresentar uma mudança interessante sobre caching, em comparação com versões anteriores. Introdução A versão 4.0 da plataforma .NET trouxe uma mudança estrutural esperada para os recursos de Cache. Nas versão 3.5 (até SP1), a plataforma fornecia uma implementação do Cache através do namespace System.Web.Caching. Nas versões anteriores o cache estava disponível no namespace System.Web, o que criada uma dependência com as classes do ASP.NET. Neste novo framework, o namespace System.Runtime.Caching reúne toda a API necessária para criar todas as tarefas comuns ao ASP.NET Caching de versões anteriores. System.Runtime.Caching e MemoryCache Tudo que precisamos para trabalhar com cache, em aplicações Web ou não, está reunido no namespace System.Runtime.Caching. A unidade básica de trabalho é a classe abstrata ObjectCache, que fornece a base para criar implementações customizadas de cache. E como é de se esperar, a classe MemoryCache é a implementação da classe abstrata ObjectCache para armazenamento das informações em memória. public class MemoryCache : ObjectCache, IEnumerable, IDisposable A utilização do cache é muito simples, bem parecida com o modelo anterior: ObjectCache cache = MemoryCache.Default; string fileContents = cache["filecontents"] as string; if (fileContents == null) { CacheItemPolicy policy = new CacheItemPolicy(); List<string> filePaths = new List<string>(); filePaths.Add("c:\\cache\\example.txt"); policy.ChangeMonitors.Add(new HostFileChangeMonitor(filePaths)); // Fetch the file contents. fileContents = File.ReadAllText("c:\\cache\\example.txt"); cache.Set("filecontents", fileContents, policy); } Label1.Text = fileContents; Extendendo o Cache É possível customizar todo mecanismo de cache através de várias abordagens. ScottGu escreveu sobre isto, que você pode acessar através deste link. Conclusão Algo muito esperado em versões anteriores, finalmente o cache está disponível sem criar relacionamento com assemblies exclusivamente Web. Perfeito para quem desenvolve outros tipos de aplicação, usufruindo deste recurso sem carregar código desnecessário. Abraços!

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  • Play Framework Plugin for NetBeans IDE

    - by Geertjan
    The start of minimal support for the Play Framework in NetBeans IDE 7.3 Beta would constitute (1) recognizing Play projects, (2) an action to run a Play project, and (3) classpath support. Well, most of that I've created already, as can be seen, e.g., below you can see logical views in the Projects window for Play projects (i.e., I can open all the samples that come with the Play distribution). Right-clicking a Play project lets you run it and, if the embedded browser is selected in the Options window, you can see the result in the IDE. Make a change to your code and refresh the browser, which immediately shows you your changes: What needs to be done, among other things: A wizard for creating new Play projects, i.e., it would use the Play command line to create the application and then open it in the IDE. Integration of everything available on the Play command line. Maybe the logical view, i.e., what is shown in the Projects window, should be changed. Right now, only the folders "app" and "test" are shown there, with everything else accessible in the Files window, as can be seen in the screenshot above. More work on the classpath, i.e., I've hardcoded a few things just to get things to work correctly. Options window extension to register the Play executable, instead of the current hardcoded solution. Scala integrations, i.e., investigate if/how the NetBeans Scala plugin is helpful and, if not, create different/additional solutions. E.g., the HTML templates are partly in Scala, i.e., need to embed Scala support into HTML. Hyperlinking in the "routes" file, as well as special support for the "application.conf" file. Anyone interested, especially if you're a Play fan (a "playboy"?), in joining me in working on this NetBeans plugin? I'll be uploading the sources to a java.net repository soon. It will be here, once it has been made publicly accessible: http://java.net/projects/nbplay/sources/nbplay Kind of cool detail is that the NetBeans plugin is based on Maven, which means that you could use any Maven-supporting IDE to work on this plugin.

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  • Apache CXF REST Services w/ Spring AOP

    - by jconlin
    I'm trying to get Apache CXF JAX-RS services working with Spring AOP. I've created a simple logging class: public class AOPLogger{ public void logBefore(){ System.out.println("Logging Before!"); } } My Spring configuration (beans.xml): <aop:config> <aop:aspect id="aopLogger" ref="test.aop.AOPLogger"> <aop:before method="logBefore" pointcut="execution(* test.rest.RestService(..))"/> </aop:aspect> </aop:config> <bean id="aopLogger" class="test.aop.AOPLogger"/> I always get an NPE in RestService when a call is made to a Method getServletRequest(), which has: return messageContext.getHttpServletRequest(); If I remove the aop configuration or comment it out from my beans.xml, everything works fine. All of my actual Rest services extend test.rest.RestService (which is a class) and call getServletRequest(). I'm just trying to just get AOP up and running based off of the example in the CXF JAX-RS documentation. Does anyone have any idea what I'm doing wrong? Thanks!

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  • Unexplained Django error. Diagnosis anyone?

    - by colorfulgrayscale
    I have a django project I keep on github. It worked perfectly fine on my laptop. I downloaded it on my desktop and tried to "python manage.py runserver" or even "python manage.py shell" I get a Error: No module named messages No other messages, no stack trace, nothing..Anyone have any idea whats going on? Thanks.

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  • Why is mod_wsgi not able to write data? IOError: failed to write data

    - by BryanWheelock
    What could be causing this error: $ sudo tail -n 100 /var/log/apache2/error.log' [Wed Dec 29 15:20:03 2010] [error] [client 220.181.108.181] mod_wsgi (pid=20343): Exception occurred processing WSGI script '/home/username/public_html/idm.wsgi'. [Wed Dec 29 15:20:03 2010] [error] [client 220.181.108.181] IOError: failed to write data Here is the WSGI script: $ cat public_html/idm.wsgi import os import sys sys.path.append('/home/username/public_html/IDM_app/') os.environ['DJANGO_SETTINGS_MODULE'] = 'settings' import django.core.handlers.wsgi application = django.core.handlers.wsgi.WSGIHandler() Why would Django not be able to write data? I'm running Django 1.2.4

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  • running python script with cron

    - by paulo
    hey guys, im trying to run a python script after every 5 minutes using cron, inside the script is a django import import django when running the crontab i get mailed the following error ImportError: No module named django this is what the crontab file looks like: [email protected] */5 * * * * /usr/bin/python /Users/paulo/Desktop/ashtanga/ping/sender.py do anyone of you know whats causing this ? btw i do have django insalled version 1.2, python 2.6, and MacOX 10.6

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  • why my code error,about serve the static file using django..

    - by zjm1126
    my settings.py: DIRNAME = os.path.dirname(__file__) STATIC_DOC_ROOT = os.path.join(DIRNAME, 'media') MEDIA_URL = '/media/' my urls.py: def google(request): return render_to_response('a.html',context_instance=RequestContext(request)) urlpatterns = patterns('', (r'^$',google), (r'^media/(?P<path>.*)$', 'django.views.static.serve',{'document_root':settings.STATIC_DOC_ROOT,'show_indexes': True}), ) and my a.html is: <script type="text/javascript" src="/media/jquery-1.4.2.js"></script> <script type="text/javascript"> alert($) </script> but,it can't defiend the '$' why ? thanks

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  • Django-imagekit: how to reduce image quality with a preprocessor_spec ?

    - by pierre-guillaume-degans
    Hi, please excuse me for my ugly english :p I've created this simple model class, with a Preprocessor to reduce my photos'quality (the photos'extension is .JPG): from django.db import models from imagekit.models import ImageModel from imagekit.specs import ImageSpec from imagekit import processors class Preprocessor(ImageSpec): quality = 50 processors = [processors.Format] class Picture(ImageModel): image = models.ImageField(upload_to='pictures') class IKOptions: preprocessor_spec = Preprocessor The problem : pictures'quality are not reduced. :( Any idea to fix it ? Thank you very much ;)

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  • How to share memory buffer across sessions in Django?

    - by afriza
    I want to have one party (or more) sends a stream of data via HTTP request(s). Other parties will be able to receive the same stream of data in almost real-time. The data stream should be accessible across sessions (according to access control list). How can I do this in Django? If possible I would like to avoid database access and use in memory buffer (along with some synchronization mechanism)

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  • What should a Django user know when moving from MySQL to PostgreSQL?

    - by tmitchell
    Most of my experience with Django thus far has been with MySQL and mysqldb. For a new app I'm writing, I'm dipping my toe in the PostgreSQL water, now that I have seen the light. While writing a data import script, I stumbled upon an issue with the default autocommit behavior. I would guess there are other "gotchas" that might crop up. What else should I be on the lookout for?

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  • How can I write this query in Django? (datetime)

    - by alex
    | time_before | datetime | YES | MUL | NULL | | | time_after | datetime | YES | MUL | NULL | | the_tag = Tag.objects.get(id=tag_id) Log.objects.filter(blah).extra(where=['last_updated >'+the_tag.time_before, 'last_updated' < the_tag.time_after]) Ok. Basically, I have an object that's called "the_tag". I want to select from Log where log.last_updated (which is a datetime field) is between the tag's time. But, I don't know how to write the last part of this Django query.

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  • how to count all distinct records in many-to-many relations in django ORM?

    - by marduk-pl
    hi, i have two models: class Project(models.Model): categories = models.ManyToManyField(Category) class Category(models.Model): name = models.CharField() now, i make some queryset: query = Project.objects.filter(id__in=[1,2,3,4]) and i like to get list of all distinct categories in this queryset with count of projects with refering to these categories - exactly i would like to get that results: category1 - 10 projects category2 - 5 projects that is opposite to this query: query2 = query.annotate(Count('categories')) what return me: project1 - 2categories project2 - 7categories how can i make it in django ORM?

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  • Are there any generic shipping calculators out there for DJango?

    - by Jon Cage
    I'm in the process of settings up a website (I'm using DJango) to begin selling some toys I build and need a way of calculating shipping costs for my customers. Are there any (preferably free) shipping calculators which accept a customers address and return the cost for different delivery companies / delivery options? It would be nice if the API could indicate cost vs delivery time. We'll be shipping world-wide if that makes a difference?

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