Improve EF DetectChanges Performance

How to Improve Entity Framework DetectChanges Performance?

When you track multiple entities in your context, then your application will suffer from performance issues causing by Entity Framework DetectChanges method.

Example

using (var ctx = new CustomerContext())
{
foreach(var line in lines)
{
var customer = new Customer();
// ...code...

// DetectChanges is invoked every time you call Add
ctx.Customers.Add(customer);
}

ctx.SaveChanges();
}

Answer

  • REDUCE the amount of entities in your context
  • REDUCE the number of DetectChanges
  • SET AutoDetectChanges to false

REDUCE the number of entities in your context

When adding/modifying multiple entities, split your logic into numerous batches to have fewer records in the context.

Why?

More tracking entities your context contains, slower the DetectChanges method is!

Performance Comparisons

Operations 100 Entities 1,000 Entities 10,000 Entities
Unlimited 15 ms 1,050 ms 105,000 ms
10 3 ms 40 ms 350 ms
100 15 ms 125 ms 1,200 ms
1,000 15 ms 1,050 ms 10,200 ms

Note:

  • *: SaveChanges time not included
  • **: Entity with two relations

How?

  1. CREATE batchSize variable
  2. CALL SaveChanges before creating a new batch
  3. CALL SaveChanges
  4. Done!

Example

// 1. CREATE batchSize variable
int batchSize = 1000;

var ctx = new CustomerContext();
for (int i = 0; i < lines.Count; i++)
{
// 2. CALL SaveChanges before creating a new batch
if (i != 0 && i%batchSize == 0)
{
ctx.SaveChanges();
ctx = new CustomerContext();
}

var customer = new Customer();
// ...code...
ctx.Customers.Add(customer);
}

// 3. CALL SaveChanges
ctx.SaveChanges();

// 4. Done!

Reduce the number of DetectChanges

When adding multiple entities, you should always use Entity Framework AddRange once with a list instead of calling various time the Add method.

Why?

  • The Add method DetectChanges after every records added.
  • The AddRange method DetectChanges after all records is added.

Performance Comparisons

Operations 100 Entities 1,000 Entities 10,000 Entities
Add 15 ms 1,050 ms 105,000 ms
AddRange 1 ms 10 ms 120 ms

Note:

  • *: SaveChanges time not included
  • **: Entity with two relations

How?

  1. CREATE a list
  2. ADD entity to the list
  3. USE AddRange with the list
  4. SaveChanges
  5. Done!

Example

using (var ctx = new CustomerContext())
{
// 1. CREATE a list
List<Customer> customers = new List<Customer>();

foreach(var line in lines)
{
var customer = new Customer();
// ...code...

// 2. ADD entity to the list
customers.Add(customer);
}

// 3. USE AddRange with the list
ctx.Customers.AddRange(customers);

// 4. SaveChanges
ctx.SaveChanges();

// 5. Done!
}

SET AutoDetectChanges to false

When adding multiple entities, if you cannot use AddRange, set Entity Framework AutoDetectChanges to false

Why?

  • The Add method DetectChanges after every records added.

By disabling AutoDetectChanges, the DetectChanges method will only be invoked when you do it.

Performance Comparisons

Operations 100 Entities 1,000 Entities 10,000 Entities
True (Default) 15 ms 1,050 ms 105,000 ms
False 1 ms 14 ms 180 ms

Note:

  • *: SaveChanges time not included
  • **: Entity with two relations

How?

  1. SET AutoDetectChangesEnabled = false
  2. CALL DetectChanges before SaveChanges
  3. SaveChanges
  4. Done!

Example

using (var ctx = new CustomerContext())
{
// 1. SET AutoDetectChangesEnabled = false
ctx.Configuration.AutoDetectChangesEnabled = false;

foreach(var line in lines)
{
var customer = new Customer();
// ...code...
ctx.Customers.Add(customer);
}

// 2. CALL DetectChanges before SaveChanges
ctx.ChangeTracker.DetectChanges();

// 3. SaveChanges
ctx.SaveChanges();

// 4. Done!
}