sb-db-common 0.1.4

A set of db wrappers

Db Common Lib

Mainly for myself, switching between different database providers all the time, I wanted a consistent interface.
Thats what this is for.
More consistent (Think ADO.NET) db connectivity

Overview

Links pgsql, mysql, mssql, oracle, sqlite and cockroachdb in a common interface
Unit tests provided to show usage

Exposed API

Import from sb_db_common:

from sb_db_common import (
    SessionFactory, Session, PersistentSession,
    ConnectionBase, MySqlConnection, PgSqlConnection, MsSqlConnection, SqliteConnection,
    OracleConnection, CockroachConnection,
    ManagedCursor, ConfigBase, RepositoryBase, TableBase,
    DataException, DatatypeException,
)
from sb_db_common.entity import entity
from sb_db_common.mapped_field import Mapped

Connections

ConnectionBase — Abstract base for all database connections. Holds connection_string, database, and connection. Subclasses implement start(), commit(), rollback(), execute(), execute_lastrowid(), fetch(), close(), and map_sql_value() (for mapping DB values to Python types). Use as a base when adding a new provider.

MySqlConnection, PgSqlConnection, MsSqlConnection, SqliteConnection, OracleConnection, CockroachConnection — Concrete connection classes for MySQL, PostgreSQL, SQL Server, SQLite, Oracle, and CockroachDB. Usually created via SessionFactory.get_connection(connection_string) rather than instantiated directly.

from sb_db_common import SessionFactory

conn = SessionFactory.get_connection("sqlite:///path/to/db.sqlite")
conn.start()
# ... use conn.execute(), conn.fetch(), etc. ...
conn.commit()
conn.close()

Session

Session — Context-managed database session. Opens the connection on __enter__, commits and closes on __exit__. Use for short-lived, transactional work.

with SessionFactory.connect("sqlite:///test.db") as session:
    session.execute("INSERT INTO test(name) VALUES (:name)", {"name": "alice"})
    id = session.execute_lastrowid("INSERT INTO test(name) VALUES (:name)", {"name": "bob"})
    row = session.fetch_one("SELECT * FROM test WHERE id = :id", {"id": id})
    val = session.fetch_scalar("SELECT COUNT(*) FROM test")
# commits and closes when the block ends

PersistentSession — Session that reuses a single global connection (e.g. for in-memory SQLite). Does not close the connection on exit; only commits. Use when you need one long-lived connection shared across multiple session blocks.

# First use: creates and keeps the connection
with SessionFactory.connect("sqlite:///memory") as session:
    session.execute("CREATE TABLE test(id INTEGER PRIMARY KEY, name TEXT)")
# Later: reuses same connection
with SessionFactory.connect("sqlite:///memory") as session:
    session.execute("INSERT INTO test(name) VALUES (:name)", {"name": "bob"})

SessionFactory — Creates sessions from connection strings. Call SessionFactory.register() once (e.g. at startup) so providers self-register. Use SessionFactory.connect(connection_string) to get a Session or PersistentSession.

SessionFactory.register()  # typically at app startup
with SessionFactory.connect("pgsql://user:pass@localhost/mydb") as session:
    session.execute("SELECT 1")

Infrastructure

ManagedCursor — Wrapper around a DB-API cursor that closes on context exit. Exposes execute(), executemany(), fetchall(), fetchone(), iteration, and properties like description (column names) and rowcount. Returned by Connection.fetch() / Session.fetch().

with SessionFactory.connect("sqlite:///test.db") as session:
    with session.fetch("SELECT id, name FROM test") as cursor:
        for row in cursor:
            print(row)
        # or: cursor.fetchall(), cursor.fetchone()

ConfigBase — Simple config holder with a connection_string. Subclass to add provider-specific or app-specific configuration.

from sb_db_common import ConfigBase

class MyConfig(ConfigBase):
    def __init__(self, connection_string: str = ""):
        super().__init__(connection_string)

Entity decorator and Mapped

@entity(table_name="...") — Decorator that turns a TableBase subclass into a full entity class. It inspects the class’s Mapped-declared fields and generates at class-definition time:

• __table_name__ — Set from the decorator argument.
• __init__(self, ...) — Constructor with one argument per non–auto-increment, non-ignored field.
• __str__(self) — String of all non-ignored field values.
• map_row(self, row, connection) — Maps a result row to instance attributes using connection.map_sql_value() for type coercion (e.g. DB datetime → Python datetime).
• get_insert_params(self) — Dict of field name → value for insert (excludes auto-increment).
• get_update_params(self) — Dict of all field names → values for update.
• get_id_params(self) — Dict of primary-key field(s) → value(s).

Use @entity(table_name="...") on a class that subclasses TableBase and declares columns with Mapped.mapped_column(...). The first time the class is built, get_fields() runs and the cache is populated; generate_queries(connection) (via repository prepare(session)) then fills the SQL script attributes on the class.

Mapped — Descriptor for entity columns. Use Mapped.mapped_column(name, field_name, field_type, order, size=50, precision=2, primary_key=False, autoincrement=False, unique=False, optional=False, default="", ignore=False) to declare a column. order is the 0-based index of the column in result rows and in generated map_row. ignore=True excludes the field from generated __init__, __str__, and param builders.

import datetime
from sb_db_common import TableBase
from sb_db_common.entity import entity
from sb_db_common.mapped_field import Mapped

@entity(table_name="product")
class Product(TableBase):
    id = Mapped.mapped_column("id", "id", int, 0, primary_key=True, autoincrement=True)
    name = Mapped.mapped_column("name", "name", str, 1, 50)
    price = Mapped.mapped_column("price", "price", float, 2, precision=2)
    created = Mapped.mapped_column("created", "created", datetime.datetime, 3)

RepositoryBase and TableBase (with generated scripts)

RepositoryBase — Base for repository-style access. Subclass and set __table__ to an entity class (a TableBase subclass built with @entity). Each repository method calls prepare(session) first; if the table’s scripts are still empty, generate_queries(session.connection) runs and fills __insert_script__, __update_script__, __fetch_by_id_script__, etc. on the table class. The repository then uses those scripts and the entity’s generated map_row, get_insert_params, and get_update_params.

Provided methods: create_schema(session), drop_schema(session), schema_exists(session), _get_by_id(session, id), _item_exists(session, id), fetch_one(session, query, params), fetch(session, query, params), count(session), add(session, item), update(session, item), _delete(session, id).

TableBase — Base for table entities. Defines get_fields() (cached list of Mapped columns, with _autoincrement_field set for add()) and generate_queries(connection), which fills the script attributes (__create_script__, __insert_script__, __update_script__, etc.) using the connection’s generate_*_query(table) methods. Entity classes use the @entity decorator to get generated map_row, get_insert_params, get_update_params, and get_id_params; you do not implement these by hand when using @entity.

from sb_db_common import RepositoryBase, SessionFactory
from sb_db_common.entity import entity
from sb_db_common.mapped_field import Mapped

# Entity (see example above)
@entity(table_name="product")
class Product(TableBase):
    id = Mapped.mapped_column("id", "id", int, 0, primary_key=True, autoincrement=True)
    name = Mapped.mapped_column("name", "name", str, 1, 50)
    # ...

class ProductRepo(RepositoryBase):
    __table__ = Product

repo = ProductRepo()
with SessionFactory.connect("sqlite:///app.db") as session:
    repo.prepare(session)  # or let add/fetch/etc. call it
    repo.create_schema(session)
    p = Product(name="widget", price=9.99)
    repo.add(session, p)   # p.id set if auto-increment
    one = repo._get_by_id(session, {"id": 1})
    items = repo.fetch(session, "SELECT * FROM product WHERE name = :name", {"name": "widget"})
    repo.update(session, p)

Exceptions

DataException — Base exception for data-layer errors (e.g. invalid connection string, invalid id).

DatatypeException — Subclass of DataException for type/conversion errors.

from sb_db_common import DataException, DatatypeException

try:
    SessionFactory.get_connection("unknown://x")
except DataException as e:
    print(e)

Usage

Connection string format is: <provider>://<username>:<password>@<host>/<database>
The supported providers are: sqlite, mysql, mssql, pgsql, oracle, cockroach

The providers self-register. Call SessionFactory.register() before use.

with SessionFactory.connect(<connection string>) as session:
    id = session.execute_lastrowid("insert into test(name) values (:name);", {"name": "bob"})
    session.execute("update test set name = :name where id = :id", {"id": id, "name": "bob1"})

The session closes and commits automatically when it goes out of scope.
For more control, manually call commit and rollback.

The queries are db specific, but the mechanisms are the same for all.
Major differences are the different field types, the parameter specification and in the use of identity columns across the different db's.
Remember to add returning <field> to the insert statement for pgsql or you won't get the identity back.

Differences

sqlite

CREATE TABLE test(
    id INTEGER NOT NULL PRIMARY KEY AUTOINCREMENT, 
    name TEXT
);

INSERT INTO test(name) VALUES (:name)

mysql

CREATE TABLE test(
    id INT NOT NULL PRIMARY KEY AUTO_INCREMENT, 
    name VARCHAR(50) NULL
);

INSERT INTO test(name) VALUES (%(name)s);

pgsql

CREATE TABLE test(
    id INT NOT NULL PRIMARY KEY GENERATED ALWAYS AS IDENTITY, 
    name VARCHAR(50) NULL
 );

INSERT INTO test(name) VALUES (%(name)s) RETURNING id;

oracle

CREATE TABLE test(
    id NUMBER GENERATED ALWAYS AS IDENTITY PRIMARY KEY, 
    name VARCHAR(50) NULL
 );

INSERT INTO test(name) VALUES (:name) RETURNING id;

mssql

CREATE TABLE test(
    id INT IDENTITY(1,1) NOT NULL PRIMARY KEY, 
    name VARCHAR(50) NULL
 );

INSERT INTO test(name) output inserted.id VALUES (%(name)s);

Integrated security is supported, either by passing in a windows username / password, or by setting trusted_connection=yes - username / password are then optional, it will then ignore them if provided, and will use the current logged in user.

Building

python -m build

Deploying

python -m twine upload --repository pypi dist/*