Use postgres unlogged tables when testing

README.md

In theory this should speed up tests running on Postgres as no WAL will be written, at the cost of completely hosing the test database if the instance crashes (which shouldn't be a problem with a test database).

When comparing builds with and without this patch applied though I had really inconsistent findings. Some builds ran much faster, but most ran much slower.

We already start postgres with the following CLI options which minimises WAL anyway, which likely renders the UNLOGGED change mostly redundant:

-c max_wal_senders=0
-c wal_level=minimal
-c min_wal_size=1024
-c fsync=off
-c full_page_writes=off

base.py

# /tests/postgres_unlogged/base.py

from django.db.backends.postgresql.base import *  # noqa: F403
from django.db.backends.postgresql.base import DatabaseWrapper as BaseDatabaseWrapper

from .schema import DatabaseSchemaEditor


class DatabaseWrapper(BaseDatabaseWrapper):  # type: ignore [no-redef]
    SchemaEditorClass = DatabaseSchemaEditor

schema.py

# /tests/postgres_unlogged/schema.py

from django.db.backends.postgresql.schema import DatabaseSchemaEditor as BaseDatabaseSchemaEditor


class DatabaseSchemaEditor(BaseDatabaseSchemaEditor):
    sql_create_table = BaseDatabaseSchemaEditor.sql_create_table.replace(
        "CREATE TABLE ", "CREATE UNLOGGED TABLE "
    )

settings.py

# /tests/settings.py

DATABASES = {
  "default": {
    "ENGINE": "tests.postgres_unlogged",
    ...
  }
}