Question
I need to insert around 2500 rows using EF Code First.
My original code looked something like this:
foreach(var item in listOfItemsToBeAdded)
{
//biz logic
context.MyStuff.Add(i);
}
This took a very long time. It was around 2.2 seconds for each DBSet.Add() call, which equates to around 90 minutes.
I refactored the code to this:
var tempItemList = new List<MyStuff>();
foreach(var item in listOfItemsToBeAdded)
{
//biz logic
tempItemList.Add(item)
}
context.MyStuff.ToList().AddRange(tempItemList);
This only takes around 4 seconds to run. However, the .ToList() queries all the items currently in the table, which is extremely necessary and could be dangerous or even more time consuming in the long run. One workaround would be to do something like context.MyStuff.Where(x=>x.ID = *empty guid*).AddRange(tempItemList) because then I know there will never be anything returned.
But I'm curious if anyone else knows of an efficient way to to a bulk insert using EF Code First?
Accepted Answer
Validation is normally a very expensive portion of EF, I had great performance improvements by disabling it with:
context.Configuration.AutoDetectChangesEnabled = false;
context.Configuration.ValidateOnSaveEnabled = false;
I believe I found that in a similar SO question--perhaps it was this answer
Another answer on that question rightly points out that if you really need bulk insert performance you should look at using System.Data.SqlClient.SqlBulkCopy. The choice between EF and ADO.NET for this issue really revolves around your priorities.
Expert Answer
As STW pointed out, the DetectChanges method called every time you call the Add method is VERY expensive.
Common solution are:
- Use AddRange over Add
- SET AutoDetectChanges to false
- SPLIT SaveChanges in multiple batches
See: Improve Entity Framework Add Performance
It's important to note that using AddRange doesn't perform a BulkInsert, it's simply invoke the DetecthChanges method once (after all entities is added) which greatly improve the performance.
But I'm curious if anyone else knows of an efficient way to to a bulk insert using EF Code First
There is some third party library supporting Bulk Insert available:
See: Entity Framework Bulk Insert library
Disclaimer: I'm the owner of Entity Framework Extensions
This library allows you to perform all bulk operations you need for your scenarios:
- Bulk SaveChanges
- Bulk Insert
- Bulk Delete
- Bulk Update
- Bulk Merge
Example
// Easy to use
context.BulkSaveChanges();
// Easy to customize
context.BulkSaveChanges(bulk => bulk.BatchSize = 100);
// Perform Bulk Operations
context.BulkDelete(customers);
context.BulkInsert(customers);
context.BulkUpdate(customers);
// Customize Primary Key
context.BulkMerge(customers, operation => {
operation.ColumnPrimaryKeyExpression =
customer => customer.Code;
});
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