Bulk Update

Definition

UPDATE all entities in the database.

All rows that match the entity key are considered as existing and are UPDATED in the database.

// Easy to use
context.BulkUpdate(list);

// Easy to customize
context.BulkUpdate(customers, options => options.ColumnPrimaryKeyExpression = customer => customer.Code);

Purpose

Updating entities using a custom key from file importation is a typical scenario.

Despite the ChangeTracker being outstanding to track what's modified, it lacks in term of scalability and flexibility.

SubmitChanges requires one database round-trip for every entity to update. So if you need to update 10000 entities, then 10000 database round-trips will be performed which is INSANELY slow.

BulkUpdate in counterpart offers great customization and requires the minimum database round-trips possible.

Performance Comparisons

Operations 1,000 Entities 2,000 Entities 5,000 Entities
SubmitChanges 1,000 ms 2,000 ms 5,000 ms
BulkUpdate 50 ms 55 ms 65 ms
## FAQ

How can I specify more than one option?

You can specify more than one option using anonymous block.

context.BulkUpdate(list, options => {
	options.BatchSize = 100);
	options.ColumnInputExpression = c => new {c.ID, c.Name, c.Description});
});

How can I specify the Batch Size?

You can specify a custom batch size using the BatchSize option.

Read more: BatchSize

context.BulkUpdate(list, options => options.BatchSize = 100);

How can I specify custom columns to Update?

You can specify custom columns using the ColumnInputExpression option.

Read more: ColumnInputExpression

context.BulkUpdate(list, options => options.ColumnInputExpression = c => new {c.Name, c.Description});

How can I specify custom keys to use?

You can specify custom key using the ColumnPrimaryKeyExpression option.

Read more: ColumnPrimaryKeyExpression

// Single Key
context.BulkUpdate(customers, options => options.ColumnPrimaryKeyExpression = customer => customer.Code);

// Surrogate Key
context.BulkUpdate(customers, options => options.ColumnPrimaryKeyExpression = customer => new { customer.Code1, customer.Code2 });

Why BulkUpdate doesn't use the ChangeTracker?

To provide the best performance possible!

Since using the ChangeTracker can greatly reduce performance, we chose to let SubmitChanges method handle scenarios with ChangeTracker and BulkUpdate, scenarios without it.

Why BulkUpdate is faster than SubmitChanges?

The major difference between both methods is SubmitChanges uses the ChangeTracker but not the BulkUpdate method.

By skipping the ChangeTracker, some methods like DetectChanges are no longer required which greatly helps to improve the performance.