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SQLAlchemy ​

SQLAlchemy is a Python SQL toolkit and ORM.

Driver ​

SQLAlchemy connects to PostgreSQL through a DBAPI driver. Use psycopg3 (postgresql+psycopg://) for the best compatibility with halephant.

SSL ​

Disable SSL in the connection URL:

db.py
python
engine = create_engine(
    "postgresql+psycopg://myapp:password@halephant:6432/myapp?sslmode=disable"
)

Read-only transactions ​

SQLAlchemy doesn't have a built-in read-only transaction mode. The simplest approach is to use a separate read-only user configured in halephant:

db.py
python
write_engine = create_engine("postgresql+psycopg://myapp:pw@halephant:6432/myapp")
read_engine = create_engine("postgresql+psycopg://myapp_ro:pw@halephant:6432/myapp")

Route sessions with a custom Session class or SQLAlchemy's horizontal sharding extension.

You can also set read_only on the underlying psycopg3 connection with an event listener:

db.py
python
from sqlalchemy import event

@event.listens_for(read_engine, "connect")
def set_readonly(dbapi_conn, connection_record):
    dbapi_conn.read_only = True

See the read replica guide for halephant configuration.