[转]How to Improve Entity Framework Add Performance?

本文转自：http://entityframework.net/improve-ef-add-performance

When you overuse the Add() method for multiple entities, your application suffers from performance issues.

using (var ctx = new CustomerContext())

    foreach(var line in lines)

        var customer = new Customer();

        // ...code...

        ctx.Customers.Add(customer);

    ctx.SaveChanges();

StackOverflow Related Questions

Answer

Is Entity Framework Add Really Slow?

In fact, the Add method is not slow at all. Adding an entity to a list cannot be that slow. It's the DetectChanges method invoked inside the Add method which is insanely slow!

Using the Add method in a loop is usually a poor practice which impacts your application performance severely when poorly used.

USE AddRange over Add (Recommended)
SET AutoDetectChanges to false
SPLIT SaveChanges in multiple batches

Use AddRange over Add (Recommended)

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

Why?

The Add method DetectChanges after every records added.
The AddRange method DetectChanges after all records are 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?

CREATE a list
ADD entity to the list
USE AddRange with the list
SaveChanges
Done!

using (var context = new EntityContext())

    // 1. CREATE a list

    List<Customer>  list = new List<Customer>();

    for(int i = 0; i < 2000; i++)

        var customer = new Customer();

        // ...code...

        // 2. ADD entity to the list

        list.Add(customer);

    // 3. USE AddRange with the list

    context.Customers.AddRange(list);

    // 4. SaveChanges

    ctx.SaveChanges();

    // 5. Done!

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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?

SET AutoDetectChangesEnabled = false
CALL DetectChanges before SaveChanges
SaveChanges
Done!

using (var context = new EntityContext())

    // 1. SET AutoDetectChangesEnabled = false

    context.Configuration.AutoDetectChangesEnabled = false;

    List<Customer>  list = new List<Customer>();

    for(int i = 0; i < 2000; i++)

        var customer = new Customer();

        // ...code...

        list.Add(customer);

    context.Customers.AddRange(list);

    // 2. CALL DetectChanges before SaveChanges

    context.ChangeTracker.DetectChanges();

    // 3. SaveChanges

    context.SaveChanges();

    // 4. Done!

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SPLIT SaveChanges into multiple batches

This solution is not recommended. When adding multiple entities, split entities with a batch size in multiple different contexts.

Why?

More tracking entities your context contains, slower the DetectChanges method is! So by reducing the number of entities by context, you improve the performance.

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

CREATE a batchSize variable
CALL SaveChanges before creating a new batch
CALL SaveChanges
Done!

// 1. CREATE a batchSize variable

int batchSize = 400;

var context = new EntityContext();

for(int i = 0; i <= 2000; i++)

    // 2. CALL SaveChanges before creating a new batch

    if (i != 0 && i%batchSize == 0)

        context.SaveChanges();

        context = new EntityContext();

    var customer = new Customer();

    // ...code...

    context.Customers.Add(customer);

// 3. CALL SaveChanges

context.SaveChanges();

// 4. Done!

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