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A non-blocking PostgreSQL query builder using Asyncio

Project description

windyquery - A non-blocking Python PostgreSQL query builder

Windyquery is a non-blocking PostgreSQL query builder with Asyncio.

Installation

$ pip install windyquery

Connection

import asyncio

from windyquery import DB

# create DB connection for CRUD operatons
db = DB()
asyncio.get_event_loop().run_until_complete(db.connect('db_name', {
    'host': 'localhost',
    'port': '5432',
    'database': 'db_name',
    'username': 'db_user_name',
    'password': 'db_user_password'
}, default=True))

asyncio.get_event_loop().run_until_complete(db.connect('other_db_name', {
    'host': 'localhost',
    'port': '5432',
    'database': 'other_db_name',
    'username': 'db_user_name',
    'password': 'db_user_password'
}, default=False))

# switch connections between different databases
db.connection('other_db_name')

# the default connection can also be changed directly
db.default = 'other_db_name'

# close DB connection
asyncio.get_event_loop().run_until_complete(db.stop())

CRUD examples

A DB instance can be used to constuct a SQL. The instance is a coroutine object. It can be scheduled to run by all asyncio mechanisms.

Build a SQL and execute it

async def main(db):
    # SELECT id, name FROM users
    users = await db.table('users').select('id', 'name')
    print(users[0]['name'])

asyncio.run(main(db))

SELECT

# SELECT name AS username, address addr FROM users
await db.table('users').select('name AS username', 'address addr')

# SELECT * FROM users WHERE id = 1 AND name = 'Tom'
await db.table('users').select().where('id', 1).where('name', 'Tom')

# SELECT * FROM users WHERE id = 1 AND name = 'Tom'
await db.table('users').select().where('id', '=', 1).where('name', '=', 'Tom')

# SELECT * FROM users WHERE id = 1 AND name = 'Tom'
await db.table('users').select().where('id = ? AND name = ?', 1, 'Tom')

# SELECT * FROM users WHERE id IN (1, 2)
await db.table('cards').select().where("id", [1, 2]))

# SELECT * FROM users WHERE id IN (1, 2)
await db.table('cards').select().where("id", 'IN', [1, 2]))

# SELECT * FROM users WHERE id IN (1, 2)
await db.table('cards').select().where("id IN (?, ?)", 1, 2))

# SELECT * FROM users ORDER BY id, name DESC
await db.table('users').select().order_by('id', 'name DESC')

# SELECT * FROM users GROUP BY id, name
await db.table('users').select().group_by('id', 'name')

# SELECT * FROM users LIMIT 100 OFFSET 10
await db.table('users').select().limit(100).offset(10)

# SELECT users.*, orders.total FROM users
#   JOIN orders ON orders.user_id = users.id
await db.table('users').select('users.*', 'orders.total').\
    join('orders', 'orders.user_id', '=', 'users.id')

# SELECT users.*, orders.total FROM users
#   JOIN orders ON orders.user_id = users.id AND orders.total > 100
await db.table('users').select('users.*', 'orders.total').\
    join('orders', 'orders.user_id = users.id AND orders.total > ?', 100)

INSERT

# INSERT INTO users(id, name) VALUES
#   (1, 'Tom'),
#   (2, 'Jerry'),
#   (3, DEFAULT)
await db.table('users').insert(
    {'id': 1, 'name': 'Tom'},
    {'id': 2, 'name': 'Jerry'},
    {'id': 3, 'name': 'DEFAULT'}
)

# INSERT INTO users(id, name) VALUES
#   (1, 'Tom'),
#   (2, 'Jerry'),
#   (3, DEFAULT)
#   RETRUNING id, name
await db.table('users').insert(
    {'id': 1, 'name': 'Tom'},
    {'id': 2, 'name': 'Jerry'},
    {'id': 3, 'name': 'DEFAULT'}
).returning('id', 'name')

# INSERT INTO users(id, name) VALUES
#   (1, 'Tom'),
#   (2, 'Jerry'),
#   (3, DEFAULT)
#   RETRUNING *
await db.table('users').insert(
    {'id': 1, 'name': 'Tom'},
    {'id': 2, 'name': 'Jerry'},
    {'id': 3, 'name': 'DEFAULT'}
).returning()

# INSERT INTO users (id, name) VALUES
#   (1, 'Tom')
#   ON CONFLICT (id) DO NOTHING
await db.table('users').insert(
    {'id': 1, 'name': 'Tom'},
).on_conflict('(id)', 'DO NOTHING')

# INSERT INTO users As u (id, name) VALUES
#   (1, 'Tom')
#   ON CONFLICT ON CONSTRAINT users_pkey
#   DO UPDATE SET name = EXCLUDED.name || ' (formerly ' || u.name || ')'
await db.table('users AS u').insert(
    {'id': 1, 'name': 'Tom'},
).on_conflict(
    'ON CONSTRAINT users_pkey',
    "DO UPDATE SET name = EXCLUDED.name || ' (formerly ' || u.name || ')'"
)        

UPDATE

# UPDATE cards SET name = 'Tom' WHERE id = 9
await db.table('cards').where('id', 9).update({'name': 'Tom'})

# UPDATE users SET name = orders.name
#   FROM orders
#   WHERE orders.user_id = users.id
await db.table('users').update('name = orders.name').\
    from_table('orders').\
    where('orders.user_id = users.id')

# UPDATE users SET name = products.name, purchase = products.name, is_paid = TRUE
#   FROM orders
#   JOIN products ON orders.product_id = products.id
#   WHERE orders.user_id = users.id
await db.table('users').update('name = product.name, purchase = products.name, is_paid = ?', True).\
    from_table('orders').\
    join('products', 'orders.product_id', '=', 'products.id').\
    where('orders.user_id = users.id')

DELETE

# DELETE FROM users WHERE id = 1
await db.table('users').where('id', 1).delete()

# DELETE FROM users WHERE id = 1 RETURNING id, name
await db.table('users').where('id', 1).delete().returning('id', 'name')

Migration examples

The DB instance can also be used to migrate database schema.

CREATE TABLE

# CREATE TABLE users (
#    id            serial PRIMARY KEY,
#    group_id      integer references groups (id) ON DELETE CASCADE,
#    created_at    timestamp not null DEFAULT NOW(),
#    email         text not null unique,
#    is_admin      boolean not null default false,
#    address       jsonb,
#    payday        integer not null,
#    CONSTRAINT unique_email UNIQUE(group_id, email)
#    check(payday > 0 and payday < 8)
#)
await db.schema('TABLE users').create(
    'id            serial PRIMARY KEY',
    'group_id      integer references groups (id) ON DELETE CASCADE',
    'created_at    timestamp not null DEFAULT NOW()',
    'email         text not null unique',
    'is_admin      boolean not null default false',
    'address       jsonb',
    'payday        integer not null',
    'CONSTRAINT unique_email UNIQUE(group_id, email)',
    'check(payday > 0 and payday < 8)',
)

# CREATE TABLE accounts LIKE users
await db.schema('TABLE accounts').create(
    'like users'
)

# CREATE TABLE IF NOT EXISTS accounts LIKE users
await db.schema('TABLE IF NOT EXISTS accounts').create(
    'like users'
)

Modify TABLE

# ALTER TABLE users
#   ALTER   id TYPE bigint,
#   ALTER   name SET DEFAULT 'no_name',
#   ALTER   COLUMN address DROP DEFAULT,
#   ALTER   "user info" SET NOT NULL,
#   ALTER   CONSTRAINT check(payday > 1 and payday < 6),
#   ADD     UNIQUE(name, email) WITH (fillfactor=70),
#   ADD     FOREIGN KEY (group_id) REFERENCES groups (id) ON DELETE SET NULL,
#   DROP    CONSTRAINT IF EXISTS idx_email CASCADE
await db.schema('TABLE users').alter(
    'alter  id TYPE bigint',
    'alter  name SET DEFAULT \'no_name\'',
    'alter  COLUMN address DROP DEFAULT',
    'alter  "user info" SET NOT NULL',
    'add    CONSTRAINT check(payday > 1 and payday < 6)',
    'add    UNIQUE(name, email) WITH (fillfactor=70)',
    'add    FOREIGN KEY (group_id) REFERENCES groups (id) ON DELETE SET NULL',
    'drop   CONSTRAINT IF EXISTS idx_email CASCADE',
)

# ALTER TABLE users RENAME TO accounts
await db.schema('TABLE users').alter('RENAME TO accounts')

# ALTER TABLE users RENAME email TO email_address
await db.schema('TABLE users').alter('RENAME email TO email_address')

# ALTER TABLE users RENAME CONSTRAINT idx_name TO index_name
await db.schema('TABLE users').alter('RENAME CONSTRAINT idx_name TO index_name')

# ALTER TABLE users ADD COLUMN address text
await db.schema('TABLE users').alter('ADD COLUMN address text')

# ALTER TABLE users DROP address
await db.schema('TABLE users').alter('DROP address')

# CREATE INDEX idx_email ON users (name, email)
await db.schema('INDEX idx_email ON users').create('name', 'email')

# CREATE UNIQUE INDEX unique_name ON users(name) WHERE soft_deleted = FALSE
await db.schema('UNIQUE INDEX unique_name ON users').create('name',).where('soft_deleted', False)

# DROP INDEX idx_email CASCADE
await db.schema('INDEX idx_email').drop('CASCADE')

# DROP TABLE users
await db.schema('TABLE users').drop()

Raw

The raw method can be used to execute any form of SQL. Usually the raw method is used to execute complex hard-coded (versus dynamically built) queries. It's also very common to use raw method to run migrations.

The input to raw method is not validated, so it is not safe from SQL injection.

RAW for complex SQL

await db.raw('SELECT ROUND(AVG(group_id),1) AS avg_id, COUNT(1) AS total_users FROM users WHERE id in ($1, $2, $3)', 4, 5, 6)

await db.raw("SELECT * FROM (VALUES (1, 'one'), (2, 'two'), (3, 'three')) AS t (num, letter)")

await db.raw("""
    INSERT INTO user (id, name)
        SELECT $1, $2 WHERE NOT EXISTS (SELECT id FROM users WHERE id = $1)
""", 1, 'Tom')

RAW for migration

await schema.raw("""
    CREATE TABLE users(
        id                       INT NOT NULL,
        created_at               DATE NOT NULL,
        first_name               VARCHAR(100) NOT NULL,
        last_name                VARCHAR(100) NOT NULL,
        birthday_mmddyyyy        CHAR(10) NOT NULL,
    )
""")

JSONB examples

Methods are created to support jsonb data type for some simple use cases.

Create a table with jsonb data type

# CREATE TABLE users (
#    id     serial PRIMARY KEY,
#    data   jsonb
#)
await db.schema('TABLE users').create(
    'id     serial PRIMARY KEY',
    'data   jsonb',
)

Select jsonb field

# SELECT data->name AS name, data->>name AS name_text FROM users
rows = await db.table('users').select('data', 'data->name AS name', 'data->>name AS name_text')
# rows[0]['data'] == '{"name":"Tom"}'
# rows[0]['name'] == '"Tom"'
# rows[0]['name_text'] == 'Tom'

# SELECT data->name AS name FROM users WHERE data->>name LIKE 'Tom%'
await db.table('users').select('data->name AS name').where('data->>name', 'LIKE', 'Tom%')

# SELECT data->name AS name FROM users WHERE data->name = '"Tom"'
await db.table('users').select('data->name AS name').where("data->name", 'Tom')

Insert jsonb field

# INSERT INTO users (data) VALUES
#   ('{"name": "Tom"}'),
#   ('{"name": "Jerry"}')
#   RETURNING *
await db.table('users').insert(
    {'data': {'name': 'Tom'}},
    {'data': {'name': 'Jerry'}},
).returning()

Update jsonb field

# UPDATE SET data = '{"address": {"city": "New York"}}'
await db.table('users').update({'data': {'address': {'city': 'New York'}}})

# UPDATE SET data = jsonb_set(data, '{address,city}', '"Chicago"')
await db.table('users').update({'data->address->city': 'Chicago'})

Listen for a notification

Postgres implements LISTEN/NOTIFY for interprocess communications. In order to listen on a channel, use the DB.listen() method. It returns an awaitable object, which resolves to a dict when a notification fires.

# method 1: manually call start() and stop()
listener = db.listen('my_table')
await listener.start()
try:
    for _ in range(100):
        result = await listener
        # or result = await listener.next()
        print(result) 
        # {
        #     'channel': 'my_table',
        #     'payload': 'payload fired by the notifier',
        #     'listener_pid': 7321,
        #     'notifier_pid': 7322
        # }
finally:
    await listener.stop()

# method 2: use with statement
async with db.listen('my_table') as listener:
    for _ in range(100):
        result = await listener
        print(result)

Tests

Windyquery includes tests. These tests are also served as examples on how to use this library.

Running tests

Install pytest to run the included tests,

pip install -U pytest

Set up a postgres server with preloaded data. This can be done by using docker with the official postgre docker image,

docker run --rm --name windyquery-test -p 5432:5432 -v ${PWD}/windyquery/tests/seed_test_data.sql:/docker-entrypoint-initdb.d/seed_test_data.sql -e POSTGRES_USER=windyquery-test -e POSTGRES_PASSWORD=windyquery-test -e POSTGRES_DB=windyquery-test -d postgres:12-alpine

Note: to use existing postgres server, it must be configured to have the correct user, password, and database needed in tests/conftest.py. Data needed by tests is in tests/seed_test_data.sql.

To run the tests,

pytest

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