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.
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using (var ctx = new CustomerContext())
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{
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foreach(var line in lines)
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{
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var customer = new Customer();
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// ...code...
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ctx.Customers.Add(customer);
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}
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ctx.SaveChanges();
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}
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!
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using (var context = new EntityContext())
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{
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// 1. CREATE a list
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List<Customer> list = new List<Customer>();
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for(int i = 0; i < 2000; i++)
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{
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var customer = new Customer();
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// ...code...
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// 2. ADD entity to the list
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list.Add(customer);
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}
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// 3. USE AddRange with the list
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context.Customers.AddRange(list);
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// 4. SaveChanges
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ctx.SaveChanges();
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// 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!
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using (var context = new EntityContext())
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{
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// 1. SET AutoDetectChangesEnabled = false
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context.Configuration.AutoDetectChangesEnabled = false;
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List<Customer> list = new List<Customer>();
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?
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for(int i = 0; i < 2000; i++)
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{
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var customer = new Customer();
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// ...code...
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list.Add(customer);
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}
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context.Customers.AddRange(list);
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// 2. CALL DetectChanges before SaveChanges
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context.ChangeTracker.DetectChanges();
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// 3. SaveChanges
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context.SaveChanges();
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// 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!
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// 1. CREATE a batchSize variable
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int batchSize = 400;
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var context = new EntityContext();
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?
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for(int i = 0; i <= 2000; i++)
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{
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// 2. CALL SaveChanges before creating a new batch
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if (i != 0 && i%batchSize == 0)
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{
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context.SaveChanges();
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context = new EntityContext();
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}
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var customer = new Customer();
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// ...code...
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context.Customers.Add(customer);
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}
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?
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// 3. CALL SaveChanges
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context.SaveChanges();
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?
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// 4. Done!
原文地址：https://www.cnblogs.com/freeliver54/p/9507049.html