peewee a django style ORM

django model

https://docs.djangoproject.com/en/3.2/topics/db/models/

django的ORM工具， 具有非常简洁的接口，遵从django快速开发的理念。

但是此工具是跟django深度绑定的， 很难独立使用。

A model is the single, definitive source of information about your data. It contains the essential fields and behaviors of the data you’re storing. Generally, each model maps to a single database table.

The basics:

• Each model is a Python class that subclasses django.db.models.Model.
• Each attribute of the model represents a database field.
• With all of this, Django gives you an automatically-generated database-access API; see Making queries.

from django.db import models

class Person(models.Model):
    first_name = models.CharField(max_length=30)
    last_name = models.CharField(max_length=30)

https://www.pythoncentral.io/sqlalchemy-vs-orms/#:~:text=%20Comparison%20Between%20Python%20ORMs%20%201%20SQLObject.,the%20unit-of-work%20concept%20which%20is%20prevalent...%20More%20

Django's ORM

Pros:

1. Easy-to-use with a short learning curve
2. Tightly integrated with Django to make it the de-factor standard when dealing with databases in Django

Cons:

1. Does not handle complex queries very well; forcing the developer to go back to raw SQL
2. Tightly integrated with Django; making it hard to use outside of a Django context

SQLAlchemy

https://www.sqlalchemy.org/

企业级持久化套件， 设计上高效和高性能的数据库访问。

SQLAlchemy is the Python SQL toolkit and Object Relational Mapper that gives application developers the full power and flexibility of SQL.

It provides a full suite of well known enterprise-level persistence patterns, designed for efficient and high-performing database access, adapted into a simple and Pythonic domain language.

https://www.pythoncentral.io/sqlalchemy-vs-orms/#:~:text=%20Comparison%20Between%20Python%20ORMs%20%201%20SQLObject.,the%20unit-of-work%20concept%20which%20is%20prevalent...%20More%20

API比较重量，学习曲线长。

Pros:

1. Enterprise-level APIs; making the code robust and adaptable
2. Flexible design; making it painless to write complex queries

Cons:

1. The Unit-of-work concept is not common
2. A heavyweight API; leading to a long learning curve

migration

https://alembic.sqlalchemy.org/en/latest/autogenerate.html

peewee

https://stackoverflow.com/questions/53428/what-are-some-good-python-orm-solutions

正解： 拥有django风格。

If you're looking for lightweight and are already familiar with django-style declarative models, check out peewee: https://github.com/coleifer/peewee

import datetime
from peewee import *

class Blog(Model):
    name = CharField()

class Entry(Model):
    blog = ForeignKeyField(Blog)
    title = CharField()
    body = TextField()
    pub_date = DateTimeField(default=datetime.datetime.now)

# query it like django
Entry.filter(blog__name='Some great blog')

# or programmatically for finer-grained control
Entry.select().join(Blog).where(Blog.name == 'Some awesome blog')

https://www.pythoncentral.io/sqlalchemy-vs-orms/#:~:text=%20Comparison%20Between%20Python%20ORMs%20%201%20SQLObject.,the%20unit-of-work%20concept%20which%20is%20prevalent...%20More%20

轻量，易于集成。

Pros:

1. A Django-ish API; making it easy-to-use
2. A lightweight implementation; making it easy to integrate with any web framework

Cons:

1. Does not support automatic schema migrations
2. Many-to-Many queries are not intuitive to write

Reference

https://github.com/coleifer/peewee

http://docs.peewee-orm.com/en/latest/peewee/quickstart.html

DB migration

peewee built-in prestage

http://docs.peewee-orm.com/en/2.10.2/peewee/playhouse.html#migrate

peewee推荐的 migration方案

缺点：

跟模型隔离， 需要单独维护一份脚本。

Schema Migrations

Peewee now supports schema migrations, with well-tested support for Postgresql, SQLite and MySQL. Unlike other schema migration tools, peewee’s migrations do not handle introspection and database “versioning”. Rather, peewee provides a number of helper functions for generating and running schema-altering statements. This engine provides the basis on which a more sophisticated tool could some day be built.

Migrations can be written as simple python scripts and executed from the command-line. Since the migrations only depend on your applications Database object, it should be easy to manage changing your model definitions and maintaining a set of migration scripts without introducing dependencies.

from playhouse.migrate import *


# SQLite example:
my_db = SqliteDatabase('my_database.db')
migrator = SqliteMigrator(my_db)


title_field = CharField(default='')
status_field = IntegerField(null=True)

migrate(
    migrator.add_column('some_table', 'title', title_field),
    migrator.add_column('some_table', 'status', status_field),
    migrator.drop_column('some_table', 'old_column'),
)

peewee-db-evolve

https://github.com/keredson/peewee-db-evolve

优点：

根据模型同步更新数据库表。

缺点：

只支持两种数据库 mysql和postgre，

不支持sqlite

Peewee DB Evolve

Diffs your models against your database, and outputs SQL to (non-destructively) update your schema.

Think of it as db.create_tables() on steriods (which doesn't drop your database).

You can also think of it as schema migrations, without having to actually write the migrations.

使用样例

https://github.com/keredson/peewee-db-evolve/tree/master/examples/hello_world

peewee_migrate

https://stackoverflow.com/questions/24906683/can-flask-peewee-do-migration

https://github.com/klen/peewee_migrate

文档不友好， 不清楚是否支持哪些数据库， 是否支持从模型生成migrations文件。

Simple migration engine for Peewee

from peewee_migrate import Router
from peewee import SqliteDatabase

router = Router(SqliteDatabase('test.db'))

# Create migration
router.create('migration_name')

# Run migration/migrations
router.run('migration_name')

# Run all unapplied migrations
router.run()

peewee_migrations

https://github.com/aachurin/peewee_migrations

命令行友好。sqlite not support。

Migrations for peewee orm.