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• Possible Performance Considerations using Linq to SQL Repositories

  - by Robert Harvey

  I have an ASP.NET MVC application that uses Linq to SQL repositories for all interactions with the database. To deal with data security, I do trimming to filter data to only those items to which the user has access. This occurs in several places: Data in list views Links in a menu bar A treeview on the left hand side containing links to content Role-based security A special security attribute, inheriting from AuthorizeAttribute, that implements content-based authorization on every controller method. Each of these places instantiates a repository, which opens a Linq to Sql DataContext and accesses the database. So, by my count, each request for a page access opens at least six separate Linq to SQL DataContexts. Should I be concerned about this from a performance perspective, and if so, what can be done to mitigate it?

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• Making all links inside of a div call the same function?

  - by Brandon

  I'm trying to make a notification area that will show alerts. return this.each(function() { jQuery('<div class="' + o['className'] + '">' + o.msg + ' + '<a href="#" onclick="$(this).parent().remove(); dismiss(' + o["id"] + ');">X</a>' + '</div>') .appendTo(this); }); This just takes a message pulled from the database, and shows it to the user. If the user clicks the X then it will call dismiss() which will mark it as being read in the database. The thing is, if the message itself contains a link to another page or external site, I also want to call dismiss() before the user leaves the page. Is there anyway to alter this javascript to take all a elements (the X and any links that would appear in the message) and change the onclick to call the function?

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• DbMetal chokes on repeated foreign key references in SQLite - any ideas?

  - by DanM

  I've been struggling to get DbMetal to process my SQLite database. I finally isolated the problem. It won't allow a table to have two foreign key references to the same column. For example, a SQLite database with these two tables will fail: CREATE TABLE Person ( Id INTEGER PRIMARY KEY, Name TEXT NOT NULL ); CREATE TABLE Match ( Id INTEGER PRIMARY KEY, WinnerPersonId INTEGER NOT NULL REFERENCES Person(Id), LoserPersonId INTEGER NOT NULL REFERENCES Person(Id) ); I get this error: DbMetal: Sequence contains more than one matching element If I get rid of the second foreign key reference, no error occurs. So, this works: CREATE TABLE Match ( Id INTEGER PRIMARY KEY, WinnerPersonId INTEGER NOT NULL REFERENCES Person(Id), LoserPersonId INTEGER NOT NULL ); But I really need both "person" columns to reference the person table. I submitted a bug report for this, but I could use a workaround in the meantime. Any ideas?

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• SQL Server - Error when trying to reference a .mdf file

  - by Amokrane

  Hi, For a NUnit test I need to reference a .mdf file from a .config file. Unfortunately, I get the following error message: The FOR ATTACH option requires that at least the primary file be specified. An attempt to attach an auto-named database for file C:\....\*.mdf A database with the same name exists, or specified file cannot be opened, or it is located on UNC share. I looked for this error on google but didn't find anything that helped me solve my problem. Any idea? Thank you

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• Connection hangs after time of inactivity

  - by Sinuhe

  In my application, Spring manages connection pool for database access. Hibernate uses these connections for its queries. At first glance, I have no problems with the pool: it works correctly with concurrent clients and a pool with only one connection. I can execute a lot of queries, so I think that I (or Spring) don't leave open connections. My problem appears after some time of inactivity (sometimes 30 minutes, sometimes more than 2 hours). Then, when Hibernate does some search, it lasts too much. Setting log4j level to TRACE, I get this logs: ... 18:27:01 DEBUG nsactionSynchronizationManager - Retrieved value [org.springframework.orm.hibernate3.SessionHolder@99abd7] for key [org.hibernate.impl.SessionFactoryImpl@7d2897] bound to thread [http-8080-Processor24] 18:27:01 DEBUG HibernateTransactionManager - Found thread-bound Session [org.hibernate.impl.SessionImpl@8878cd] for Hibernate transaction 18:27:01 DEBUG HibernateTransactionManager - Using transaction object [org.springframework.orm.hibernate3.HibernateTransactionManager$HibernateTransactionObject@1b2ffee] 18:27:01 DEBUG HibernateTransactionManager - Creating new transaction with name [com.acjoventut.service.GenericManager.findByExample]: PROPAGATION_REQUIRED,ISOLATION_DEFAULT 18:27:01 DEBUG HibernateTransactionManager - Preparing JDBC Connection of Hibernate Session [org.hibernate.impl.SessionImpl@8878cd] 18:27:01 TRACE SessionImpl - setting flush mode to: AUTO 18:27:01 DEBUG JDBCTransaction - begin 18:27:01 DEBUG ConnectionManager - opening JDBC connection Here it gets frozen for about 2 - 10 minutes. But then continues: 18:30:11 DEBUG JDBCTransaction - current autocommit status: true 18:30:11 DEBUG JDBCTransaction - disabling autocommit 18:30:11 TRACE JDBCContext - after transaction begin 18:30:11 DEBUG HibernateTransactionManager - Exposing Hibernate transaction as JDBC transaction [jdbc:oracle:thin:@212.31.39.50:30998:orcl, UserName=DEVELOP, Oracle JDBC driver] 18:30:11 DEBUG nsactionSynchronizationManager - Bound value [org.springframework.jdbc.datasource.ConnectionHolder@843a9d] for key [org.apache.commons.dbcp.BasicDataSource@7745fd] to thread [http-8080-Processor24] 18:30:11 DEBUG nsactionSynchronizationManager - Initializing transaction synchronization ... After that, it works with no problems, until another period of inactivity. IMHO, it seems like connection pool returns an invalid/closed connection, and when Hibernate realizes that, ask another connection to the pool. I don't know how can I solve this problem or things I can do for delimiting it. Any help achieving this will be appreciate. Thanks. EDIT: Well, it finally was due a firewall rule. Database detects the connection is lost, but pool (dbcp or c3p0) not. So, it tries to query the database with no success. What is still strange for me is that timeout period is very variable. Maybe the rule is specially strange or firewall doesn't work correctly. Anyway, I have no access to that machine and I can only wait for an explanation. :(

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• Using protocol buffers for a comprehensive data strategy for Windows Mobile devices

  - by Steve

  I have started reading some of the posts related to protocol buffers. The serialization method seems very appropriate for the transfer of data to and from web servers. Has anyone considered using a method like this to save and retrieve data on the mobile device itself? (i.e. a replacement for a traditional database / orm layer) Where would the data be persisted? How would the data be queried? Would it make sense to store the data in a traditional database (SqlCE or SqlLite) with a few "searchable" columns and then one column for the serialized data? Thoughts? Am I out on a limb here? Thank you!

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• The best way to separate admin functionality from a public site?

  - by AndrewO

  I'm working on a site that's grown both in terms of user-base and functionality to the point where it's becoming evident that some of the admin tasks should be separate from the public website. I was wondering what the best way to do this would be. For example, the site has a large social component to it, and a public sales interface. But at the same time, there's back office tasks, bulk upload processing, dashboards (with long running queries), and customer relations tools in the admin section that I would like to not be effected by spikes in public traffic (or effect the public-facing response time). The site is running on a fairly standard Rails/MySQL/Linux stack, but I think this is more of an architecture problem than an implementation one: mainly, how does one keep the data and business logic in sync between these different applications? Some strategies that I'm evaluating: 1) Create a slave database of the public facing database on another machine. Extract out all of the model and library code so that it can be shared between the applications. Create new controllers and views for the admin interfaces. I have limited experience with replication and am not even sure that it's supposed to be used this way (most of the time I've seen it, it's been for scaling out the read capabilities of the same application, rather than having multiple different ones). I'm also worried about the potential for latency issues if the slave is not on the same network. 2) Create new more task/department-specific applications and use a message oriented middleware to integrate them. I read Enterprise Integration Patterns awhile back and they seemed to advocate this for distributed systems. (Alternatively, in some cases the basic Rails-style RESTful API functionality might suffice.) But, I have nightmares about data synchronization issues and the massive re-architecting that this would entail. 3) Some mixture of the two. For example, the only public information necessary for some of the back office tasks is a read-only completion time or status. Would it make sense to have that on a completely separate system and send the data to public? Meanwhile, the user/group admin functionality would be run on a separate system sharing the database? The downside is, this seems to keep many of the concerns I have with the first two, especially the re-architecting. I'm sure the answers are going to be highly dependent on a site's specific needs, but I'd love to hear success (or failure) stories.

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• creating XSD schema files for GAC dll

  - by Raj More

  How can I use XSD.exe to create an XML schema for the Microsoft.AnalysisServices.Database object?

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• How can you configure or extend BITS (Background Intelligent Transfer Service) to read files from a

  - by Mark

  I have a ASP .NET load balanced application (webservice and website). It runs on SQL server. I need to be able to provide large files for download. However, because of the load balancing situation, the files are stored in the SQL database as opposed to the file system. BITS seems to be the best approach. I have full control of the client. However, i don't know how to configure BITS to read the file from the database. I know how to write the C# code for that, but i don't know how to get BITS to hook into it as opposed to reading the file from the file system. Any ideas?

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• Zend_Session: unserialize session data

  - by takeshin

  I'm using session SaveHandler to persist session data in the database. Sample session_data column from the database: Messenger|a:1:{s:13:"page_messages";a:0:{}}userSession|a:1:{s:7:"referer";s:32:"http://cms.dev/user/profile/view";}Zend_Auth|a:1:{s:7:"storage";O:19:"User_Model_Identity":3:{s:2:"id";s:1:"1";s:8:"username";s:13:"administrator";s:4:"slug";s:13:"administrator";}} I want to delete Zend_Auth object from this session data. How can I unserialize those objects and remove object I need? I suspect, that I don't have to write my custom parser, that Zend_Session already has a method to do this. I have tried different combinations of unserialize but it still returns false. I'm using autoloader from ZF 1.10.2 and Doctrine 1.2

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• ghc can't find my cabal installed packages

  - by nont

  I've installed ghc 6.12.3, and then the Haskell Platform. I'm trying to compile a test program: $ ghc test.hs test.hs:3:0: Failed to load interface for `Bindings': Use -v to see a list of the files searched for. so, naturally, I do cabal install Bindings Which works fine, and places the package in ~/.cabal/lib/bindings-0.1.2 The problem is, that when I go to compile again with ghc, it still doesn't find the package I've installed with cabal. compiling in verbose mode gives: ghc -v test.hs Using binary package database: /home/ludflu/ghc/lib/ghc-6.12.3/package.conf.d/package.cache Using binary package database: /home/ludflu/.ghc/x86_64-linux 6.12.3/package.conf.d/package.cache As suggested by another stackoverflow user, I tried: ghc-pkg describe rts > rts.pkg vi rts.pkg # add the /home/ludflu/.cabal/lib to `library-dirs` field ghc-pkg update rts.pkg But to no avail. How to I add the .cabal to the list of package directories to search? Thank you!

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• MySQL script to delete data in chunks until everything lower then id has been deleted

  - by Chriswede

  I need an MySQL Skript which does the following: delete chunks of the database until it has deleted all link_id's greater then 10000 exmaple: x = 10000 DELETE FROM pligg_links WHERE link_id > x and link_id < x+10000 x = x + 10000 ... So it would delete DELETE FROM pligg_links WHERE link_id > 10000 and link_id < 20000 then DELETE FROM pligg_links WHERE link_id > 20000 and link_id < 30000 until all id's less then 10000 have been removed I need this because the database is very very big (more then a gig) thank in advance

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• Is a class that is hard to unit test badly designed?

  - by Extrakun

  I am now doing unit testing on an application which was written over the year, before I started to do unit-testing diligently. I realized that the classes I wrote are hard to unit test, for the following reasons: Relies on loading data from database. Which means I have to setup a row in the table just to run the unit test (and I am not testing database capabilities). Requires a lot of other external classes just to get the class I am testing to its initial state. On the whole, there don't seem to be anything wrong with the design except that it is too tightly coupled (which by itself is a bad thing). I figure that if I have written automated test cases with each of the class, hence ensuring that I don't heap extra dependencies or coupling for the class to work, the class might be better designed. Does this reason holds water? What are your experiences?

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• Trouble using Prototype JS

  - by user309381

  I have three files named like: AjxDm.php db_test website.php What I am trying to do is AjxDm.php in this file I click and I am using Ajax.Request and it directed me to the db_test.php. In this file I am retrieving a value from the database and I assign the value into a dropdown. Again when I try to select one of the options in the dropdown it is direceting me to the Website.php using Ajax.Request with the dropdown selected value and retrieve data from database and display. The problem is that when I call from AjxDm.php to Db_test it works but when I select option in db_test.php it doesn't find a JavaScript function which direct me to the website.php. What can I do to make it work?

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• Save BLOB to disk as Image C#

  - by TGuimond

  Hello, I am developing a web application that calls web services developed by a third party to send/receive data from a clients database. I am building the application using ASP.NET 3.5 C#. The way that they are providing me images is in BLOB format. I call their method and what I get back is a DataSet with 2 fields "logo_name" and "logo" which is the BLOB field. What I want to do is: Save the image locally on the disk (to minimize calls to their database in the future). I have been playing around with a couple of different ways of doing this but cannot seem to get the image to save correctly. I have been able to create a file in a folder with the correct name but if I try to view the image it does not work. I was hoping someone could give me some sample code to show me how to save a BLOB field to the local disk? Thanks

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• Java/MySQL: Working with data in classes

  - by skiwi

  What is the best way to deal with accessing/modifying tables in a database? I have read about the Data Access Object approach, but none of the resources I have found so far indicate a clear implementation of it. So assume you have a database with a table called accounts that has columns id, name, password and email. How would you properly access it within Java? I mean most people know how to do SQL statements, but that is not really the point. I hope people here can be of help. Regards.

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• MySQL PHP incompatibility.

  - by Evernoob

  Ok maybe I've overlooked something really simple here, but I can't seem to figure this out. I'm running WAMP locally, but connecting to a remote MySQL database. The local version of PHP is the latest 5.3.0. One of the remote databases, being version 5.0.45 works fine. However, the other remote database I'm trying to connect to, which is version 5.0.22 throws the following error before dying: Warning: mysql_connect() [function.mysql-connect]: OK packet 6 bytes shorter than expected. PID=5880 in ... Warning: mysql_connect() [function.mysql-connect]: mysqlnd cannot connect to MySQL 4.1+ using old authentication in ... WTF? UPDATE: Reverting to PHP 5.2.* i.e. anything lower than 5.3.0 resolves the problem completely. As long as I am not running 5.3.0 I can connect to both databases. I'm not sure what the explanation is for this weirdness.

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• Document Management System - Where to Store Files?

  - by Diego AC

  Hey, stack! I'm on charge of building an ASP.NET MVC Document Management System. It have to be able to do basic document management tasks like adding, editing and searching entries and also perform versioning. Anyways, I'm targeting PDF, Office and many image formats as the file attached to each document entry in the database. My question is: What design guidelines do pros follow when building the storage mechanism? Do they store the document files in the file system? Database? How file uploading is handled? I used to upload the files to a temporal location while the user was editing the data and move it to permanent storage when the user confirmed the entry creation. Is this good? Any suggestions on improvement?

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• MySQL ALTER TABLE on very large table - is it safe to run it?

  - by Timothy Mifsud

  I have a MySQL database with one particular MyISAM table of above 4 million rows. I update this table about once a week with about 2000 new rows. After updating, I then perform the following statement: ALTER TABLE x ORDER BY PK DESC i.e. I order the table in question by the primary key field in descending order. This has not given me any problems on my development machine (Windows with 3GB memory), but, even though 3 times I have tried it successfully on the production Linux server (with 512MB RAM - and achieving the resulted sorted table in about 6 minutes each time), the last time I tried it I had to stop the query after about 30 minutes and rebuild the database from a backup. I have started to wonder whether a 512MB server can cope with that statement (on such a large table) as I have read that a temporary table is created to perform the ALTER TABLE command?! And, if it can be safely run, what should be the expected time for the alteration of the table? Thanks in advance, Tim

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• Performance - User defined query / filter to search data

  - by Cagatay Kalan

  What is the best way to design a system where users can create their own criterias to search data ? By "design" i mean, data storage, data access layer and search structure. We will actually refactor an existing application which is written in C# and ASP .NET and we don't want to change the infrastructure. Our main issue is performance and we use MSSQL and DevExpress to build queries. Some queries run in 4-5 minutes and all the columns included in the queries have indexes. When i check queries, i see that DevExpress builds too many "exists" clauses and i'm not happy with that because i have doubts that some of these queries skip some indexes. What may be the alternatives to DevExpress? NHibernate or Entity Framework? Can we build dynamic criteria system and store these to database in both of them ? And also do we need any alternative storage like a lucene index or OLAP database?

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• translating specifications into query predicates

  - by Jeroen

  I'm trying to find a nice and elegant way to query database content based on DDD "specifications". In domain driven design, a specification is used to check if some object, also known as the candidate, is compliant to a (domain specific) requirement. For example, the specification 'IsTaskDone' goes like: class IsTaskDone extends Specification<Task> { boolean isSatisfiedBy(Task candidate) { return candidate.isDone(); } } The above specification can be used for many purposes, e.g. it can be used to validate if a task has been completed, or to filter all completed tasks from a collection. However, I want to re-use this, nice, domain related specification to query on the database. Of course, the easiest solution would be to retrieve all entities of our desired type from the database, and filter that list in-memory by looping and removing non-matching entities. But clearly that would not be optimal for performance, especially when the entity count in our db increases. Proposal So my idea is to create a 'ConversionManager' that translates my specification into a persistence technique specific criteria, think of the JPA predicate class. The services looks as follows: public interface JpaSpecificationConversionManager { <T> Predicate getPredicateFor(Specification<T> specification, Root<T> root, CriteriaQuery<?> cq, CriteriaBuilder cb); JpaSpecificationConversionManager registerConverter(JpaSpecificationConverter<?, ?> converter); } By using our manager, the users can register their own conversion logic, isolating the domain related specification from persistence specific logic. To minimize the configuration of our manager, I want to use annotations on my converter classes, allowing the manager to automatically register those converters. JPA repository implementations could then use my manager, via dependency injection, to offer a find by specification method. Providing a find by specification should drastically reduce the number of methods on our repository interface. In theory, this all sounds decent, but I feel like I'm missing something critical. What do you guys think of my proposal, does it comply to the DDD way of thinking? Or is there already a framework that does something identical to what I just described?

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• NHibernate 'IdentifierGenerationException' on an Update trigger

  - by Jan Jongboom

  In my database I have an id column defined as [autonumber] [int] IDENTITY(1,1) NOT NULL which is mapped in my .hbm.xml like: <id name="Id" column="autonumber" type="int"> <generator class="identity" /> </id> When calling session.Save() updates are successful committed to the database. When adding a versioning trigger I however get the error this id generator generates Int64, Int32, Int16 of type IdentifierGenerationException. The trigger is defined as: ALTER TRIGGER [dbo].[CatchUpdates_NVM_FDK_Kenmerken] ON [dbo].[NVM_FDK_Kenmerken] INSTEAD OF UPDATE AS BEGIN SET NOCOUNT ON UPDATE NVM_FDK_Kenmerken SET idIsActive = 0 WHERE internalId IN (SELECT internalId FROM INSERTED) INSERT INTO dbo.NVM_FDK_Kenmerken ( vestigingNummer , internalId , someOtherColumns, dateInserted, idIsActive ) SELECT vestigingNummer, internalId, someOtherColumns, GETDATE(), 1 FROM INSERTED END What am I doing wrong here? When doing manual updates everything works just fine and as expected.

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• First Fluent NHibernate Project

  - by Andy

  I'm trying to follow the "Your first project" tutorial at http://wiki.fluentnhibernate.org/Getting_started and have hit a roadblock. When I try to run the console application, I'm getting this error: An invalid or incomplete configuration was used while creating a SessionFactory. Check PotentialReasons collection, and InnerException for more detail. I have created a SQLite database "firstProject.db" and referenced the full path to the file in the call to: return Fluently.Configure() .Database(SQLiteConfiguration.Standard .UsingFile(DbFile)) .Mappings(m => m.FluentMappings.AddFromAssemblyOf<Program>()) .ExposeConfiguration(BuildSchema) .BuildSessionFactory(); so I don't know what I'm doing wrong. What/where is this "PotentialReasons" collection? Thank you for the help. Andy

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• PHP + MYSQLI: Variable parameter/result binding with prepared statements.

  - by Brian Warshaw

  In a project that I'm about to wrap up, I've written and implemented an object-relational mapping solution for PHP. Before the doubters and dreamers cry out "how on earth?", relax -- I haven't found a way to make late static binding work -- I'm just working around it in the best way that I possibly can. Anyway, I'm not currently using prepared statements for querying, because I couldn't come up with a way to pass a variable number of arguments to the bind_params() or bind_result() methods. Why do I need to support a variable number of arguments, you ask? Because the superclass of my models (think of my solution as a hacked-up PHP ActiveRecord wannabe) is where the querying is defined, and so the find() method, for example, doesn't know how many parameters it would need to bind. Now, I've already thought of building an argument list and passing a string to eval(), but I don't like that solution very much -- I'd rather just implement my own security checks and pass on statements. Does anyone have any suggestions (or success stories) about how to get this done? If you can help me solve this first problem, perhaps we can tackle binding the result set (something I suspect will be more difficult, or at least more resource-intensive if it involves an initial query to determine table structure).

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• Linq to SQL code generator features

  - by Anders Abel

  I'm very fond of Linq to SQL and the programming model it encourages. I think that in many cases when you are in control of both the database schema and the code it is not worth the effort to have different relational and object models for the data. Working with Linq to SQL makes it simple to have type safe data access from .NET, using the partial extension methods to implement business rules. Unfortunately I do not like the dbml designer due to the lack of a schema refresh function. So far I have used SqlMetal, but that lacks the customization options of the dbml designer. Because of that I've started working on a tool which regenerates the whole code file like SqlMetal, but has the ability to do the customizations that are available in the dbml designer (and maybe more in the future). The customizations will be described in an xml file which only contains those parts that shouldn't have default values. This should keep the xml file size down as well as the maintenance burden of it. To help me focus on the right features, I would like to know: What would be your favourite feature in a linq to sql code generator?

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