varco-sa 0.0.2

SQLAlchemy async backend for varco — runtime ORM generation, repository, schema guard, and Alembic helpers

varco-sa

SQLAlchemy async backend for varco.

Generates SQLAlchemy ORM classes at runtime from your DomainModel subclasses — no hand-written ORM models needed. Requires varco-core.

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Install

pip install varco-sa

# With PostgreSQL async driver:
pip install "varco-sa[postgresql]"

# With SQLite (tests / local dev):
pip install "varco-sa[sqlite]"

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Features

• Zero-boilerplate ORM — SAModelFactory generates DeclarativeBase subclasses at runtime; no duplication between domain and ORM layers
• Full async repository — AsyncSQLAlchemyRepository implements AsyncRepository (CRUD, exists(), stream_by_query() with server-side cursor)
• Unit of Work — SQLAlchemyUnitOfWork manages AsyncSession lifecycle and atomic commits
• One-liner bootstrap — SAFastrestApp + SAConfig wire engine, session factory, ORM generation, and table creation
• Alembic integration — get_target_metadata() and print_create_ddl() helpers for migration scripts
• Schema Guard — SchemaGuard detects drift between ORM metadata and the live database schema
• Query integration — accepts varco-core QueryParams / QueryBuilder AST natively; translates to SQLAlchemy where() clauses

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What's in the package

Module	Purpose
factory.py	SAModelFactory — generates DeclarativeBase subclasses at runtime; SAModelRegistry — escape hatch
repository.py	AsyncSQLAlchemyRepository — AsyncSession-backed CRUD + exists() + stream_by_query()
uow.py	SQLAlchemyUnitOfWork — session lifecycle + atomic commits
provider.py	SQLAlchemyRepositoryProvider — wires factory + repos + UoW
bootstrap.py	SAConfig, SAFastrestApp — one-liner app setup
alembic_helpers.py	get_target_metadata, print_create_ddl — Alembic integration
schema_guard.py	SchemaGuard — drift detection between ORM metadata and live DB

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Quick start

Bootstrap (one-liner)

from sqlalchemy.ext.asyncio import create_async_engine
from sqlalchemy.orm import DeclarativeBase
from varco_sa import SAConfig, SAFastrestApp

class Base(DeclarativeBase): pass

engine = create_async_engine("postgresql+asyncpg://user:pass@localhost/mydb")

app = SAFastrestApp(SAConfig(
    engine=engine,
    base=Base,
    entity_classes=(User, Post),
))

await app.create_all()              # CREATE TABLE IF NOT EXISTS ...
uow_provider = app.uow_provider     # ready to inject as IUoWProvider

Manual setup

from sqlalchemy.ext.asyncio import async_sessionmaker
from varco_sa import SQLAlchemyRepositoryProvider

sessions = async_sessionmaker(engine, expire_on_commit=False)
provider = SQLAlchemyRepositoryProvider(engine=engine, session_factory=sessions)
provider.register(User, Post)
await provider.create_all()

async with provider.make_uow() as uow:
    user = await uow.users.save(User(name="Edo", email="[e-mail]"))
    print(user.pk)

Query integration

from varco_core import QueryBuilder, QueryParams

async with provider.make_uow() as uow:
    # exists() — uses SA identity-map cache, no full ORM load when cached
    if await uow.posts.exists(post_id):
        ...

    # stream_by_query() — server-side cursor, constant memory regardless of result size
    params = QueryParams(node=QueryBuilder().eq("active", True).build())
    async for post in uow.posts.stream_by_query(params):
        await process(post)

Alembic integration

# alembic/env.py
from varco_sa import get_target_metadata
from myapp.models import User, Post

target_metadata = get_target_metadata(User, Post)

Preview the DDL before running a migration:

from varco_sa import print_create_ddl

print(print_create_ddl(User, Post, dialect="postgresql"))

Schema Guard — detect drift

from varco_sa import SchemaGuard

guard = SchemaGuard(engine, User, Post)
differences = await guard.check()
if differences:
    print("Schema drift detected:", differences)

Access the generated SA model (escape hatch)

from varco_sa import SAModelRegistry
from sqlalchemy.orm import relationship

UserORM = SAModelRegistry.get(User)
UserORM.posts = relationship("PostORM", back_populates="author")

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Related packages

Package	Description
varco-core	Domain model, service layer, query AST, JWT — required dependency
varco-beanie	Beanie / Motor MongoDB backend (alternative to this package)

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Links

• Repository: https://github.com/edoardoscarpaci/varco
• Full docs: https://github.com/edoardoscarpaci/varco#sqlalchemy-backend
• Issue tracker: https://github.com/edoardoscarpaci/varco/issues