No migration occurs as expected when adding unique=True to field

[licongy]

No migration occurs as expected when adding unique=True to field.

For example, if you originally had a model:

class Example(models.Model):
    id = SnowflakeIDField()
    name = fields.CharField(max_length=64, null=False, db_index=True)

then you add a constraint to the name field:

class Example(models.Model):
    id = SnowflakeIDField()
    name = fields.CharField(max_length=64, null=False, db_index=True, unique=True)

the migration you expect to get should be:

async def upgrade(db: BaseDBAsyncClient) -> str:
    return """
        DROP INDEX IF EXISTS "idx_example_name_a7b9a6";
        CREATE UNIQUE INDEX "idx_example_name_a7b9a6" ON "example" ("name");
        """

or at least:

async def upgrade(db: BaseDBAsyncClient) -> str:
    return """
        ALTER TABLE "example"
        ADD CONSTRAINT "example_name_a7b9a6" UNIQUE ("name");
        """

However, the practical result is that no migration files are produced.

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Version:
aerich : 0.8.1 ac847ba
tortoise-orm : 0.23.0
asyncpg : 0.30.0
postgresql : 17.2
python : 3.12