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# microcosm-postgres Opinionated persistence with PostgreSQL. [](https://circleci.com/gh/globality-corp/microcosm-postgres/tree/develop) ## Usage This project includes example models and persistence stores. Assuming the testing database exists (see below), the following demonstrates basic usage: from microcosm.api import create_object_graph from microcosm_postgres.context import SessionContext, transaction from microcosm_postgres.example import Company # create the object graph graph = create_object_graph(name="example", testing=True) # wire up the persistence layer to the (testing) database [company_store] = graph.use("company_store") # set up a session with SessionContext(graph) as context: # drop and create database tables; *only* do this for testing context.recreate_all() with transaction(): # create a model company = company_store.create(Company(name="Acme")) # prints 1 print company_store.count() ## Convention Basics: - Databases are segmented by microservice; no service can see another's database - Every microservice connects to its database with a username and a password - Unit testing uses an real (non-mock) database with a non-overlapping name - Database names and usernames are generated according to convention Models: - Persistent models use a `SQLAlchemy` declarative base class - Persistent operations pass through a unifying `Store` layer - Persistent operations favor explicit queries and deletes over automatic relations and cascades ## Configuration To change the database host: config.postgres.host = "myhost" To change the database password: config.postgres.password = "mysecretpassword" ## Test Setup Tests (and automated builds) act as the "example" microservice and need a cooresponding database and user: createuser example createdb -O example example_test_db Note that production usage should always create the user with a password. For example: echo "CREATE ROLE example WITH LOGIN ENCRYPTED PASSWORD 'secret';" | psql Automated test do not enforce that a password is set because many development environments (OSX, Circle CI) configure `pg_hba.conf` for trusted login from localhost.