Peewee mysql Failed creating unique index on TextField field

Question

I am trying to create a model with unique index.

My models look like that:

class ModelA(Model):
    FieldA = CharField()

class ModelB(Model):
    fieldA = TextField(unique=True)
    fieldB = CharField(max_length=10)
    fieldC = BooleanField(default=False)
    fieldD = ForeignKeyField(ModelA)

And I'm creating the tables like this:

db.create_tables([ModelA, ModelB])

My problem is that after creating the table there's no index on ModelB.fieldA.

When I changed ModelB.fieldA type to CharField instead of TextField:

class ModelA(Model):
    FieldA = CharField()

class ModelB(Model):
    fieldA = CharField(unique=True)
    fieldB = CharField(max_length=10)
    fieldC = BooleanField(default=False)
    fieldD = ForeignKeyField(ModelA)

It works properly and an index is created for ModelB.fieldA.

Is there any reason I can't create a unique index on TextField field type? How can I create a unique index on ModelB.fieldA and keeping it's type TextField?

Thanks

Answer 1

MySQL requires you to specify a prefix for indexes on text type: https://dev.mysql.com/doc/refman/8.0/en/create-index.html#create-index-column-prefixes

So you will want an index like:

CREATE INDEX my_index ON my_model(text_column (100));