Концепт ORM

orm.py

class ModelOptions:
  ...


class ModelMeta(type):
  
  def __new__(mcls, name, bases, attrs):
    cls = super().__new__(mcls, name, bases, attrs)
    # if name == 'Model':
    #   return cls
    parents = [b for b in bases[::-1] if isinstance(b, mcls)]
    if not parents:
      return cls
    cls._fields = ...
    cls._opts = ...
    ...
    cls.objects = ModelManager(cls)
    return cls
  

class ModelManager:
  
  def __init__(self, model):
    self.model = model
   
  @propery
  def db(self):
    return self.model.__database__
    
  async def scalar(self, *, using_db=None):
    db = using_db or self.db
    ...
  
  async def first(self, *, using_db=None):
    db = using_db or self.db
    ...
    
  async def all(self, *, using_db=None):
    db = using_db or self.db
    ...


class Model(metaclass=ModelMeta):
  
  async def save(self, *, using_db=None):
    ...

  
class Employe(Model):
  ...


employe = Employe(first_name='John', last_name='Doe', position='Python Programmer')

await employe.save()
# INSERT INTO employees (first_name, last_name) VALUES (%s, %s);

employe.position = 'Teamlead'
await employe.save()
# UPDATE employees SET position = %s WHERE id = %s;

await employe.remove()
# DELETE FROM employees WHERE id = %s;

await Employe.objects.where(Employe.company_id == 123).order_by(Employe.salary.desc())[25:50].all()
# SELECT employees.* FROM employees WHERE (employees.company_id = %s) ORDER BY employees.salary DESC LIMIT 25 OFFSET 50;

await Employe.objects.where(Employe.company_id == 123).avg(Employe.salary).scalar()
# SELECT AVG(employees.salary) FROM employees WHERE (employees.company_id = %s);

await Employe.objects.where(Employe.company_id == 123 & Employe.salary == fn.MAX(Employe.salary)).first()
# SELECT employees.* FROM employees WHERE ((employees.company_id = %s) AND (employees.salary = MAX(employees.salary)) LIMIT 1 OFFSET 0;

https://searchcode.com/file/54131568/svarga/contrib/appengine/models/gae.py#l-1

sql/__init__.py:

sql/nodes.py:

class Node:
  def accept(self, v):
     v.visit(self)

sql/visitors.py:

class Visitor:
  
  def visit(self, node):
    method = 'visit_' + node.__class__.__name__
    getattr(self, method)(node)