ORM

该orm包是一个用于Python的异步ORM，支持Postgres、MySQL和SQLite。ORM使用

• SQLAlchemy核心进行查询构建。
• databases提供跨数据库异步支持。
• typesystem进行数据验证。

由于ORM建立在SQLAlchemy核心之上，您可以使用Alembic提供数据库迁移。

ORM仍在开发中：我们建议使用orm~=0.1固定任何依赖项

注意：由于它支持await，请使用ipython在控制台中尝试此操作。

import databases
import orm
import sqlalchemy

database = databases.Database("sqlite:///db.sqlite")
metadata = sqlalchemy.MetaData()


class Note(orm.Model):
    __tablename__ = "notes"
    __database__ = database
    __metadata__ = metadata

    id = orm.Integer(primary_key=True)
    text = orm.String(max_length=100)
    completed = orm.Boolean(default=False)

# Create the database
engine = sqlalchemy.create_engine(str(database.url))
metadata.create_all(engine)

# .create()
await Note.objects.create(text="Buy the groceries.", completed=False)
await Note.objects.create(text="Call Mum.", completed=True)
await Note.objects.create(text="Send invoices.", completed=True)

# .all()
notes = await Note.objects.all()

# .filter()
notes = await Note.objects.filter(completed=True).all()

# exact, iexact, contains, icontains, lt, lte, gt, gte, in
notes = await Note.objects.filter(text__icontains="mum").all()

# .get()
note = await Note.objects.get(id=1)

# .update()
await note.update(completed=True)

# .delete()
await note.delete()

# 'pk' always refers to the primary key
note = await Note.objects.get(pk=2)
note.pk  # 2

ORM支持通过外键加载和过滤...

import databases
import orm
import sqlalchemy

database = databases.Database("sqlite:///db.sqlite")
metadata = sqlalchemy.MetaData()


class Album(orm.Model):
    __tablename__ = "album"
    __metadata__ = metadata
    __database__ = database

    id = orm.Integer(primary_key=True)
    name = orm.String(max_length=100)


class Track(orm.Model):
    __tablename__ = "track"
    __metadata__ = metadata
    __database__ = database

    id = orm.Integer(primary_key=True)
    album = orm.ForeignKey(Album)
    title = orm.String(max_length=100)
    position = orm.Integer()


# Create some records to work with.
malibu = await Album.objects.create(name="Malibu")
await Track.objects.create(album=malibu, title="The Bird", position=1)
await Track.objects.create(album=malibu, title="Heart don't stand a chance", position=2)
await Track.objects.create(album=malibu, title="The Waters", position=3)

fantasies = await Album.objects.create(name="Fantasies")
await Track.objects.create(album=fantasies, title="Help I'm Alive", position=1)
await Track.objects.create(album=fantasies, title="Sick Muse", position=2)


# Fetch an instance, without loading a foreign key relationship on it.
track = await Track.objects.get(title="The Bird")

# We have an album instance, but it only has the primary key populated
print(track.album)       # Album(id=1) [sparse]
print(track.album.pk)    # 1
print(track.album.name)  # Raises AttributeError

# Load the relationship from the database
await track.album.load()
assert track.album.name == "Malibu"

# This time, fetch an instance, loading the foreign key relationship.
track = await Track.objects.select_related("album").get(title="The Bird")
assert track.album.name == "Malibu"

# Fetch instances, with a filter across an FK relationship.
tracks = Track.objects.filter(album__name="Fantasies")
assert len(tracks) == 2

# Fetch instances, with a filter and operator across an FK relationship.
tracks = Track.objects.filter(album__name__iexact="fantasies")
assert len(tracks) == 2

# Limit a query
tracks = await Track.objects.limit(1).all()
assert len(tracks) == 1

数据类型

以下关键字参数支持所有字段类型。

• primary_key
• allow_null
• default
• index
• unique

除非设置了以下之一，否则所有字段都是必需的

• allow_null - 创建一个可空列。默认设置为None。
• allow_blank - 允许空字符串进行验证。默认设置为""。
• default - 为字段设置默认值。

以下列类型被支持。有关特定类型的验证关键字参数，请参阅TypeSystem的文档。

• orm.String(max_length)
• orm.Text()
• orm.Boolean()
• orm.Integer()
• orm.Float()
• orm.Date()
• orm.Time()
• orm.DateTime()
• orm.JSON()