PGAdapter - SQLAlchemy 2.x Connection Options

PGAdapter supports SQLAlchemy 2.0.1 and higher.

Limitations

PGAdapter supports SQLAlchemy 2.x with Cloud Spanner PostgreSQL databases. It has been tested with SQLAlchemy 2.0.1 and psycopg 3.1.8. Developing new applications using SQLAlchemy 2.x is possible as long as the listed limitations are taken into account. Porting an existing application from PostgreSQL to Cloud Spanner is likely to require code changes.

PGAdapter does not support SQLAlchemy 2.x with any other engines than psycopg 3.x. Using psycopg2 with SQLAlchemy 2.x is not supported.

See Limitations in the sqlalchemy2-sample directory for a full list of limitations.

Usage

First start PGAdapter:

export GOOGLE_APPLICATION_CREDENTIALS=/path/to/credentials.json
docker pull gcr.io/cloud-spanner-pg-adapter/pgadapter
docker run \
  -d -p 5432:5432 \
  -v ${GOOGLE_APPLICATION_CREDENTIALS}:${GOOGLE_APPLICATION_CREDENTIALS}:ro \
  -e GOOGLE_APPLICATION_CREDENTIALS \
  gcr.io/cloud-spanner-pg-adapter/pgadapter \
  -p my-project -i my-instance \
  -x

Then connect to PGAdapter and use SQLAlchemy 2.x like this (note the use of psycopg and NOT psycopg2):

conn_string = "postgresql+psycopg://user:password@localhost:5432/my-database"
engine = create_engine(conn_string)
with Session(engine) as session:
  user1 = User(
    name="user1",
    fullname="Full name of User 1",
    addresses=[Address(email_address="user1@sqlalchemy.org")]
  )
  session.add(user1)
  session.commit()

Full Sample and Limitations

This directory contains a full sample of how to work with SQLAlchemy 2.x with Cloud Spanner and PGAdapter. The sample readme file also lists the current limitations when working with SQLAlchemy 2.x.