orm1 0.2.1

Object-relational mapping library for PostgreSQL

orm1

orm1 is a minimal asynchronous Object-Relational Mapping (ORM) library for Python that makes it easy to map your Python classes to PostgreSQL database tables. Built on top of asyncpg, orm1 provides a minimal yet powerful API for CRUD operations, complex query building, and relationship management – all with full async support.

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Features

• Asynchronous by Design
  Leverage Python’s async/await syntax with an asyncpg backend for high-performance, non-blocking database operations.

• Auto-mapping with Type Hints
  Automatically generate entity mappings from your class type hints. orm1 infers column names (using snake_case conversion) and even detects relationships (both singular and plural) based on your annotations—greatly reducing boilerplate.

• Aggregate Support (Parent-Child Relationship)
  Define aggregates naturally by specifying child entities that are part of an aggregate. For instance, a Post aggregate can include multiple PostAttachment instances.

• Fluent Query Builder
  Construct complex SQL queries using a Pythonic API. orm1 supports filtering, joins, ordering, and pagination, all while keeping your code readable.

• Raw SQL Queries with Safe Parameter Binding
  Execute raw SQL queries while benefitting from an internal SQL Abstract Syntax Tree (AST) that safely binds parameters, protecting against SQL injection.

• Flexible Transaction Management
  Start and commit transactions with ease, using the session’s transaction context manager tx.

• Composite Key Support
  orm1 supports both single and composite keys for primary and parental keys. When multiple fields are specified, orm1 automatically combines them into a tuple key for consistent entity identification.

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Installation

Install orm1 from PyPI with pip:

pip install orm1

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Getting Started

Defining Your Entities

Define your entity classes with type hints to describe fields and relationships. Use the auto.mapped decorator from the AutoMappingBuilder to register your classes with orm1. Column names are automatically generated (using snake_case conversion) unless overridden in the configuration.

Below is an example using a Post aggregate with its child PostAttachment:

from orm1 import auto

@auto.mapped(
    table="posts",
    primary_key="id"
)
class Post:
    id: int
    title: str
    content: str
    # Define the aggregate relationship: a post has many attachments.
    attachments: list["PostAttachment"]

@auto.mapped(
    table="post_attachments",
    primary_key="id",
    parental_key="post_id"  # Indicates this entity belongs to a Post aggregate.
)
class PostAttachment:
    id: int
    post_id: int
    file_name: str
    url: str

The mappings above assume that you have a PostgreSQL database with tables posts and post_attachments. The PostAttachment table has a foreign key post_id that references the id column of the posts table.

CREATE TABLE posts (
    id SERIAL PRIMARY KEY,
    title TEXT NOT NULL,
    content TEXT NOT NULL
);

CREATE TABLE post_attachments (
    id SERIAL PRIMARY KEY,
    post_id INT NOT NULL REFERENCES posts(id),
    file_name TEXT NOT NULL,
    url TEXT NOT NULL
);

Composite Key Example

orm1 also supports composite keys. Simply provide a list of field names for primary_key (or parental_key) in your mapping configuration:

@auto.mapped(
    table="user_roles",
    primary_key=["user_id", "role_id"]
)
class UserRole:
    user_id: int
    role_id: int
    # additional fields...

In this case, orm1 will automatically combine user_id and role_id into a tuple key for entity identification.

Building Mappings

After decorating your entity classes, build the mappings. This process collects the configuration and type hints to create the internal mapping definitions used by orm1.

from orm1 import auto

mappings = auto.build()

Creating a Session

Create a session to interact with your database. The session uses a backend (such as AsyncPGSessionBackend) for executing SQL statements.

import asyncpg
from orm1 import Session, AsyncPGSessionBackend

async def main():
    # Create an asyncpg connection pool.
    pool = await asyncpg.create_pool(dsn="postgresql://user:password@localhost/dbname")
    
    # Initialize the backend and session.
    backend = AsyncPGSessionBackend(pool)
    session = Session(backend, mappings)
    
    # Now you can perform CRUD operations with your session.

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CRUD Operations

Inserting and Saving Entities

To insert a new entity or update an existing one, simply call save on your session. orm1 will determine whether to insert or update based on whether the entity is already tracked.

# Create a new post with an attachment.
post = Post()
post.title = "Introducing orm1"
post.content = "orm1 is a lightweight asynchronous ORM for Python."

attachment = PostAttachment()
attachment.file_name = "diagram.png"
attachment.url = "http://example.com/diagram.png"

post.attachments = [attachment]

# Save the post (and cascade save the attachment as part of the aggregate).
await session.save(post)

Querying Entities

Use the query builder to fetch entities with filtering, joins, and ordering.

# Query for a post by title.
query = session.query(Post, alias="p")
query = query.where('p."title" = :title', title="Introducing orm1")
posts = await query.fetch()

# Get a single post.
post = await query.fetch_one()

Updating Entities

Modify the attributes of an entity and call save again. orm1 will automatically update the corresponding database record.

# Update the post's title.
post.title = "Introducing orm1 - A Lightweight Async ORM"
await session.save(post)

Deleting Entities

Remove an entity by calling delete on the session. Deleting an aggregate root will cascade and remove its child entities as needed.

await session.delete(post)

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Transactions

Use the session’s transaction context manager tx to start and commit transactions.

async with session.tx():
    post = await session.get(Post, 1)
    post.title = "Transaction Test"
    await session.save(post)

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Advanced Querying

Joining Related Entities

Join related tables by using the join or left_join methods on a query. This is useful when you need to filter or retrieve data based on relationships.

# Join post attachments with their parent posts.
query = session.query(PostAttachment, "a")
query = query.join(Post, "p", 'a.post_id = p.id')
query = query.where('p.title = :title', title="Introducing orm1")
attachments = await query.fetch()

Ordering and Pagination

Sort your query results and paginate them easily.

# Ordering: specify ascending or descending order.
query = session.query(PostAttachment, "a")
query = query.order_by(query.asc('a.file_name'))
attachments = await query.fetch(limit=10, offset=0)

# Pagination: use paginate to get page information.
page = await query.paginate(first=10)
print("Attachment cursors on current page:", page.cursors)
print("Has next page?", page.has_next_page)

Executing Raw SQL Queries

If you need more control, execute raw SQL statements while still benefiting from safe parameter binding.

raw_query = session.raw("SELECT * FROM post_attachments WHERE file_name LIKE :pattern", pattern="%diagram%")
results = await raw_query.fetch()

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Auto-mapping and Relationship Detection

orm1’s auto-mapping leverages Python’s type hints to automatically generate entity mappings:

• Field Mapping: Fields without explicit configuration are automatically mapped to columns using a snake_case conversion.
• Relationship Detection:
  • If an attribute is annotated as a list of another mapped entity, orm1 interprets it as a one-to-many relationship.
  • If an attribute is annotated as an optional entity (e.g., Optional[Entity]), it’s treated as a singular relationship.

This auto-detection reduces manual configuration and simplifies managing aggregate entities and their children.

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API Reference

Session

• get(entity_type, id)
  Retrieve a single entity by its primary key.

• save(entity)
  Insert or update an entity (and its children, if applicable).

• delete(entity)
  Delete an entity (and cascade delete its children).

• query(entity_type, alias)
  Start building a query for the given entity type.

• raw(query, **params)
  Create a raw SQL query.

• tx()
  Start a new transaction.

SessionEntityQuery

• where(condition, **params)
  Add a where condition to the query.

• join(target, alias, on, **params) / left_join(target, alias, on, **params)
  Join another table (or entity) into the query.

• having(condition, **params)
  Add a having condition to the query.

• order_by(...)
  Specify ordering for the query results.

• fetch(limit, offset)
  Execute the query and retrieve a list of entities.

• fetch_one()
  Retrieve a single entity.

• count()
  Count the number of matching entities.

• paginate(first, after, last, before, offset)
  Paginate the query results.

AutoMappingBuilder

• @auto.mapped(**kwargs)
  Decorator to register and configure an entity’s mapping. Configuration options include specifying the table name, primary key (single or composite), parental key, field configurations, and child (relationship) configurations.

• auto.build()
  Build and return all entity mappings based on the registered configurations.

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License

This project is licensed under the Apache License.