Always run migration on datetime column when using TiDB

[Thearas]

• The issue is present in the latest release.
• I have searched the issues of this repository and believe that this is not a duplicate.

Current Behavior 😯

Ent always run migration on datetime column when using TiDB, even if the schema in the database is already up to date.

Expected Behavior 🤔

No migration.

Steps to Reproduce 🕹

Steps:

1. Create a schema with fields created_at datetime(6):

// ent/schema/user.go
type User struct {
	ent.Schema
}

func (User) Fields() []ent.Field {
	return []ent.Field{field.Time("created_at").
		Immutable().
		Default(time.Now).
		SchemaType(map[string]string{
				dialect.MySQL: "datetime(6)",
		}),
	}
}

2. Generate DB migration in offline mode, and then apply the SQLs to TiDB:

BEGIN;
CREATE TABLE IF NOT EXISTS `users`(`id` bigint AUTO_INCREMENT NOT NULL, `created_at` datetime(6) NOT NULL, PRIMARY KEY(`id`)) CHARACTER SET utf8mb4 COLLATE utf8mb4_bin;
COMMIT;

3. Repeat step 2. But every time I execute step 2, I got the same SQLs:

BEGIN;
ALTER TABLE `users` MODIFY COLUMN `created_at` datetime(6) NOT NULL;
COMMIT;

Your Environment 🌎

Tech	Version
Go	1.17.2
Ent	0.9.2
Database	TiDB v5.1.2
Driver	https://github.com/go-sql-driver/mysql

[godcong]

Have you tried it under mysql?
If there is no such exception, it is possible that there is a compatibility issue with tidb.
(I am using the same environment as you: ent+tidb, :)

[Thearas]

Have you tried it under mysql?

It works fine on MySQL 8.0.27.

[hedwigz]

Hey @Thearas 😄
With the new migration engine, Atlas, this is now resolved.
Upgrade to entgo.io/ent@master and use schema.WithAtlas(true)

client.Schema.Create(context.Background(), schema.WithAtlas(true))

[Thearas]

Great! It works for me! @hedwigz

However, I found that Atlas does not support WithForeignKeys(false):

ent/migrate: sql/schema: WithForeignKeys(false) does not work in Atlas migration

Any plans to support WithForeignKeys(false)?

[zeevmoney]

Hi @Thearas 👋🏻

Soon this will be solved via #2404

[zeevmoney]

@Thearas updating you that the PR was merged :)
#2404