Technology Research of Entity Framework2

[daisukenishino]

Questions about EntityFramework

We have a variety of questions about EntityFramework.
We will request an investigation of the following questions to you.

Memory usage

We believe that EntityFramework behave as follows.

• DbContext.xxxx() (xxxx is the table name)
  • If you call the above method, to hold all of the records in the table on the memory.
  • It is unclear to get at any stage. (When the DbContext generation? When the table access ?)
• DbContext.Database.SqlQuery("...SQL statement...")
  • I have thought that result set of the SQL statement is hold on the memory.

Updating with ExecuteSqlCommand

• If you use this method, you can freely run the SQL statement. However, SQL statements can be executed regardless of the contents of the entity. Therefore, I think that contents of the entity and database do not match after execution of this method.
• If it is the behavior as described above, there is a need to refresh the contents of the entities?
  • c# - How do I Refresh DbContext - Stack Overflow
    http://stackoverflow.com/questions/18169970/how-do-i-refresh-dbcontext

Connection / Transaction management of SaveChanges method

• Behavior of SaveChanges is as follows
  • Open the connection.
  • Start a transaction.
  • Perform a query (*1).
  • Finishe the transaction
  • Successful completion ... commit
  • Abnormal termination (exception) ... roll back
  • Close the connection
  • [Reference] Entity Framework - Try to check the transaction in the log output(ログ出力でトランザクションを確認してみる)
    http://ichiroku11.hatenablog.jp/entry/2014/04/16/232004
• For matter of "* 1", when you look at the code of the Entity Framework from the following URL, each time entry.AcceptChanges method is executed against a record of change in a foreach in the AcceptAllChanges method.
  • Entity Framework - Source Code
    http://entityframework.codeplex.com/SourceControl/latest#src/EntityFramework/Core/Objects/ObjectContext.cs
• For this reason, Entity Framework so that is doing the update instruction from the program for each of changed records. Round-trip between the APServer and DBServer occurs in such a processing method. Therefore, I think about the performance of problem occurs in the batch processing of large amounts of data processing.
• Since the connection / transaction is created every time you call the SaveChanges method, Following (a) and (b) to use a different connection / another transaction. If you want to explicitly manage transactions, it is written the way to "treat as a single transaction(1つのトランザクションとして扱う)" in the above-referenced site.
  • Correct the Entity call the SaveChanges method (a)
  • Correct the Entity call the SaveChanges method (b)
• For this reason, I think that it may dispense with as much as possible a single call to SaveChanges method. However, in the following case I think that there is a need to manage the explicit connection / transaction.
  • If you need to call more than once SaveChanges method.
  • When used in combination the SaveChanges method and ExecuteSqlCommand methods.
  • When used in combination the SaveChanges method and stored procedures.

There is something like a Better use in Entity Data Model how to make?

For example, either "divide the Entity Data Model in arbitrary units" or "entities combine into a single Entity Data Model".

• If you wrap the Entity to one of the Entity Data Model, it is easy to combine multiple entity update to the call of a single SaveChanges method.
• If you divide the Entity multiple of Entity Data Model, there is a need to call multiple times SaveChanges method. Therefore connection / transaction explicit management is required.

[daisukenishino]

We summarized research results as follows(written by Japanese).

• Entity Framework - マイクロソフト系技術情報 Wiki
  http://techinfoofmicrosofttech.osscons.jp/index.php?Entity%20Framework
• Entity Framework の調査 - マイクロソフト系技術情報 Wiki
  http://techinfoofmicrosofttech.osscons.jp/index.php?Entity%20Framework%20%E3%81%AE%E8%AA%BF%E6%9F%BB