aerie 0.5.2

An async database toolkit.

Aerie

A wrapper around SQLAlchemy made to support asynchronous workloads.

Aerie - is an avariel (or winged elf) from Baldur's Gate II game.

Installation

Install aerie using PIP or poetry:

pip install aerie[postgresql]
# or
poetry add aerie[postgresql]

For SQLite use "sqlite" extra. To install all drivers use "full" extra.

Features

• full async/await support
• plain SQL with bound params
• SQLAlchemy query builders support
• SQLAlchemy ORM support
• pagination

TODO

• simplify column definition: sa.Column(sa.Integer) -> models.IntergerField()
• integrate with Alembic CLI
• multiple metadata objects support (for multiple distinct databases)

Quick start

See example application in examples/ directory of this repository.

Usage

As this library is based on SQLAlchemy, it is strictly recommended getting yourself familiar with it.

A general usage is:

• create an instance of Aerie
• define ORM models
• create tables in the database (or, preferably, use Alembic migrations)
• obtain a session and perform database queries

Aerie instance

Create an instance of Aerie class and pass a connection string to it:

from aerie import Aerie

db = Aerie('sqlite+aiosqlite:///tmp/database.sqlite2')
# or
db = Aerie('postgresql+asyncpg://postgres:postgres@localhost/aerie')

You need appropriate driver installed. Add "aiosqlite" for SQLite support, or add "asyncpg" for PostreSQL support.

Raw SQL queries

At this step Aerie is ready to work. Create a new transaction and execute any query you need.

from sqlalchemy.sql import text

# assuming "users" table exists
sql = text('select * from users where user_id = :user_id')
rows = await db.query(sql, {'user_id': 1}).all()

Full listing examples/raw_sql.py

Using query builder

Sure, you are not limited to plain SQL. SQLAlchemy query builders also supported (because Aerie is a tiny layer on top of the SQLAlchemy)

from sqlalchemy.sql import text
import sqlalchemy as sa
from aerie import metadata

users = sa.Table(
    'users', metadata,
    sa.Column(sa.Integer, name='id', primary_key=True),
    sa.Column(sa.String, name='name'),
)

# create tables
await db.create_tables()

stmt = select(users).where(users.c.id == 2)
rows = await db.query(stmt).all()

Full listing examples/tables.py

Using ORM models and sessions

Another option to low-level query builder are ORM models. Aerie provides aerie.Model class that you should extend to create your model.

from aerie import Model
import sqlalchemy as sa


class User(Model):
    __tablename__ = 'users'

    id = sa.Column(sa.Integer, primary_key=True)
    name = sa.Column(sa.String)


# create tables
await db.create_tables()

async with db.session() as session:
    session.add_all([
        User(id=1, name='One'),
        User(id=2, name='Two'),
        User(id=3, name='Three'),
    ])
    await session.flush()

    # get first user in the row set
    stmt = session.select(User)
    user = await session.query(stmt).first()

Make sure the module with models is imported before you create tables. Otherwise they will not be added to the metadata and, thus, not created.

Full listing examples/orm.py

Pagination

Aerie's DbSession ships with pagination utilities out of the box. When you need to paginate a query just call DbSession.paginate method.

async with db.session() as session:
    stmt = session.select(User)
    page = await session.query(stmt).paginate(page=1, page_size=10)

    for user in page:
        print(user)

    print('Next page: %s' % page.next_page)
    print('Previous page: %s' % page.previous_page)
    print('Displaying items: %s - %s' % (page.start_index, page.end_index))

The page object has more helper attributes:

Property	Type	Description
total_pages	int	Total pages in the row set.
has_next	bool	Test if the next page is available.
has_previous	bool	Test if the previous page is available.
has_other	bool	Test if there are another pages except current one.
next_page	int	Next page number. Always returns an integer. If there is no more pages the current page number returned.
previous_page	int	Previous page number. Always returns an integer. If there is no previous page, the number 1 returned.
start_index	int	The 1-based index of the first item on this page.
end_index	int	The 1-based index of the last item on this page.
total_rows	int	Total rows in result set.

Alembic migrations

Alembic usage is well documented in the official docs: Using Asyncio with Alembic

Note, you need to use aerie.metadata when you configure target_metadata option:

# migrations/env.py

from aerie import metadata

...

target_metadata = metadata

...

Also, don't forget to import all your models in Alembic's env.py file so their structure is fully loaded and no models forgotten.