Linq to Sql: How to quickly clear a table

I like using an Extension Method, per the following:

public static class LinqExtension
{
  public static void Truncate<TEntity>(this Table<TEntity> table) where TEntity : class
  {
    var rowType = table.GetType().GetGenericArguments()[0];
    var tableName = table.Context.Mapping.GetTable(rowType).TableName;
    var sqlCommand = String.Format("TRUNCATE TABLE {0}", tableName);
    table.Context.ExecuteCommand(sqlCommand);
  }
}

Unfortunately LINQ-to-SQL doesn't execute set based queries very well.

You would assume that

context.Entities.DeleteAllOnSubmit(context.Entities); 
context.SubmitChanges(); 

will translate to something like

DELETE FROM [Entities]

but unfortunately it's more like

DELETE FROM [dbo].[Entities] WHERE ([EntitiesId] = @p0) AND ([Column1] = @p1) ...
DELETE FROM [dbo].[Entities] WHERE ([EntitiesId] = @p0) AND ([Column1] = @p1) ...
DELETE FROM [dbo].[Entities] WHERE ([EntitiesId] = @p0) AND ([Column1] = @p1) ...

You'll find the same when you try to do bulk update in LINQ-to-SQL. Any more than a few hundred rows at a time and it's simply going to be too slow.

If you need to do batch operations & you're using LINQ-to-SQL, you need to write stored procedures.

You could do a normal SQL truncate or delete command, using the DataContext.ExecuteCommand method:

context.ExecuteCommand("DELETE FROM Entity");

Or

context.ExecuteCommand("TRUNCATE TABLE Entity");

The way you are deleting is taking long because Linq to SQL generates a DELETE statement for each entity, there are other type-safe approaches to do batch deletes/updates, check the following articles:

• Batch Updates and Deletes with LINQ to SQL
• LINQ to SQL Extension: Batch Deletion with Lambda Expression