Databases
StackOverflow2013
Postsdbo
PO
 

Note that there are some explanatory texts on larger screens.

plurals
  1. PO
    primarykey
    data
    text
    <p>I have been using entity framework(V1.0) for about a year in my current project. We have 100s of tables,all added to the edmx. Problems we face (though not sure if the new entity framework resolves these issues)</p> <ol> <li><p>When you are used to VS.net IDE, you will be used to doing all drag/drop operations from your IDE. The problem is, once your edmx hosts 100s of tables,the IDE really stalls and you would have to wait for 3-4 minutes before it becomes responsive</p></li> <li><p>With so many tables ,any edits you do on the edmx take long.</p></li> <li><p>When you are going to use a version control, comparing 10000 line XML is quite painful. Think about merging 2 branches each having a 10000 line edmx,the tables, new association between tables, deleted associations and going back and forth comparing xmls. You would need a good xml comparison tool if you are serious about merging 2 big edmx files</p></li> <li><p>For performance reasons we had to make the csdl,msl and ssdl as embedded resources</p></li> <li><p>Your edmx should have to be in sync with your DB all the time,or at least, when you try to update the edmx, it will try to sync and might throw some obscure errors if they are out of sync.</p></li> <li><p>Be aware that your entities(tables/views) should always have a primary key, else you will get obscure errors. See my <a href="https://stackoverflow.com/questions/3111112/entity-framework-result-discrepancy-for-a-database-views">other question here</a></p></li> </ol> <p>Things We did/I might consider in the future when using EF</p> <ol> <li><p>Use multiple edmx by using 1 edmx for tables logically grouped/linked together. Be aware of the fact that if you do this, each edmx should live in its own namespace. If you try to add 2 related tables(say person &amp; address) to 2 edmx in the same namespace, you will get a compiler error stating that the foreign key relationship is already defined. (Tip: create a folder and create the edmx under this folder. If you try to alter the namespace in the edmx without having the folder, it does not save properly the namespace the next time you open/edit it)</p> <pre><code>fewer tables in edmx =&gt; less heavy container =&gt; good </code></pre> <p>fewer tables in edmx=> easier to merge when merging 2 branches</p></li> <li><p>Be aware of the fact that object context is not thread safe</p></li> <li><p>Your repository (or what ever DAO you use) should be responsible for creating and disposing the container it creates. Using DI frameworks, especially in a web app complicated things for us. Web requests are served from the threadpool and the container were not disposed properly after the web request was served as the thread itself was not disposed. The container got reused (when the thread was reused) and created a lot of concurrency issues</p></li> <li><p>Don't trust your VS IDE. Get a good XML editor and know how to edit the edmx file (though you don't need to edit the designer). Get your hands dirty</p></li> <li><p><strong>ALWAYS ALWAYS ALWAYS</strong> (just cannot emphasize this enough) run a SQL profiler (and I mean each and every step of your code) when you execute your queries. As complex as the query might look, you will be surprised to find how many times you hit the DB Example:(sorry, unable to get code to the right format,can someone format it ?)</p> <pre><code>var myOrders = from t in context.Table where t.CustomerID=123 </code></pre> <p>select t; //above query not yet executed</p> <p><code>if(myOrders.Count&gt;0)//DB query to find count { var firstOrder = myOrders.First()//DB query to get first result }</code></p> <p>Better approach</p> <p>// query materialized, just 1 hit to DB as we are using ToList() var myOrders = (from t in Context.tables where t.customerID=123 select t).ToList();</p> <pre><code>if(myOrders.Count&gt;0)//no DB hit { //do something var myOrder = myOrders[0];//no DB hit } </code></pre></li> <li><p>Know when to use tracking and no tracking(for read-only) and web apps do a lot of reads than writes. Set them properly when you initialize your container</p></li> <li><p>Did I forget compiled queries ? Look <a href="http://www.albahari.com/nutshell/speedinguplinqtosql.aspx" rel="nofollow noreferrer">here</a> for more goodies</p></li> <li><p>When getting 1000s of rows back from your DB, make sure you use IQueryable and <a href="http://msdn.microsoft.com/en-us/library/bb738697.aspx" rel="nofollow noreferrer">detach the objectContext</a> so that you don't run out of memory</p></li> </ol> <p><strong>Update:</strong></p> <p><a href="http://thedatafarm.com/blog/" rel="nofollow noreferrer">Julie Lerman</a> address the same problem with a <a href="http://thedatafarm.com/blog/data-access/creating-models-from-databases-with-billions-of-tables/" rel="nofollow noreferrer">similar solution</a>. Her post also points to <a href="http://www.ideablade.com/WardsCorner/WardsCorner_home.aspx" rel="nofollow noreferrer">Ward</a>'s work on dealing with <a href="http://www.ideablade.com/WardsCorner/LargeEFModels.pdf" rel="nofollow noreferrer">huge number of tables</a></p>
    singulars
    1. This table or related slice is empty.
    1. POIs ADO.NET Entity Framework (with ASP.NET MVC v2) a viable option when writing custom and contantly updated websites?
      singulars
      1. PTQuestion
    1. PTAnswer
    1. USCommunity
    1. USram
    plurals
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. POIs ADO.NET Entity Framework (with ASP.NET MVC v2) a viable option when writing custom and contantly updated websites?
      singulars
      1. PTQuestion
    1. This table or related slice is empty.
    1. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    2. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    3. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    1. COone other informative post http://stackoverflow.com/questions/547278/what-are-good-design-practices-when-working-with-entity-framework
      singulars
      1. PO
      1. USram
    2. CO@Ram - Thanks a ton for such a detailed post. I can't really tell if you're advocating using entity or not because you're using EF but you list a few problems/headaches that you've had. You also of course post tips to avoid those problems (because I'm new to EF a lot of it is greek to me as of yet.) Overall, are you saying it's worth it to implement the new technology in a fast-paced, custom setting?
      singulars
      1. PO
      1. USquakkels
    3. COGo for it.Go for the latest one.And I would be curious to see if I can use T4 (though not sure if I can customize the SQL which is getting fired). Always watch over the queries(and the left joins) when you do a "include" on your objectContext.Table. Update your knowledge with books/blogs and ofcourse StackOverflow. Few months down the lane, you will be a EF geek !! Good Luck
      singulars
      1. PO
      1. USram
 

Querying!

 
Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload