I have a fast api app used to handle data base migrations with alembic and sql alchemy as per this example:
https://github.com/nf1s/fastapi_sqlalchemy_alembic/blob/master/alembic/env.py
The .env file in my alembic directory looks like this :
from logging.config import fileConfig
from sqlalchemy import engine_from_config
from sqlalchemy import pool
from alembic import context
# Loading .env variables in order to inject postgres db url into configuration
import os, sys
from dotenv import load_dotenv
BASE_DIR = os.path.dirname(os.path.dirname(os.path.abspath(__file__)))
load_dotenv(os.path.join(BASE_DIR, ".env"))
sys.path.append(BASE_DIR)
# this is the Alembic Config object, which provides
# access to the values within the .ini file in use.
config = context.config
# this will overwrite the ini-file sqlalchemy.url path
# with the path given in the config of the main code
config.set_main_option("sqlalchemy.url", os.environ["OPERATIONAL_DATABASE_URL"])
# Interpret the config file for Python logging.
# This line sets up loggers basically.
if config.config_file_name is not None:
fileConfig(config.config_file_name)
# add your model's MetaData object here
# for 'autogenerate' support
# from myapp import mymodel
# target_metadata = mymodel.Base.metadata
import models
from models import *
target_metadata = models.Base.metadata
# other values from the config, defined by the needs of env.py,
# can be acquired:
# my_important_option = config.get_main_option("my_important_option")
# ... etc.
def run_migrations_offline() -> None:
"""Run migrations in 'offline' mode.
This configures the context with just a URL
and not an Engine, though an Engine is acceptable
here as well. By skipping the Engine creation
we don't even need a DBAPI to be available.
Calls to context.execute() here emit the given string to the
script output.
"""
url = config.get_main_option("sqlalchemy.url")
context.configure(
url=url,
target_metadata=target_metadata,
literal_binds=True,
dialect_opts={"paramstyle": "named"},
)
with context.begin_transaction():
context.run_migrations()
def run_migrations_online() -> None:
"""Run migrations in 'online' mode.
In this scenario we need to create an Engine
and associate a connection with the context.
"""
connectable = engine_from_config(
config.get_section(config.config_ini_section, {}),
prefix="sqlalchemy.",
poolclass=pool.NullPool,
)
with connectable.connect() as connection:
context.configure(
connection=connection, target_metadata=target_metadata
)
with context.begin_transaction():
context.run_migrations()
if context.is_offline_mode():
run_migrations_offline()
else:
run_migrations_online()
My models.py file looks like this:
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy import Column, Integer, String
Base = declarative_base()
class User(Base):
__tablename__ = "users"
id = Column(Integer, primary_key=True, index=True)
first_name = Column(String,)
last_name = Column(String)
age = Column(Integer)
My alembic.ini file looks like this:
# A generic, single database configuration.
[alembic]
# path to migration scripts
script_location = alembic
# template used to generate migration file names; The default value is %%(rev)s_%%(slug)s
# Uncomment the line below if you want the files to be prepended with date and time
# see https://alembic.sqlalchemy.org/en/latest/tutorial.html#editing-the-ini-file
# for all available tokens
# file_template = %%(year)d_%%(month).2d_%%(day).2d_%%(hour).2d%%(minute).2d-%%(rev)s_%%(slug)s
# sys.path path, will be prepended to sys.path if present.
# defaults to the current working directory.
prepend_sys_path = .
# timezone to use when rendering the date within the migration file
# as well as the filename.
# If specified, requires the python-dateutil library that can be
# installed by adding `alembic[tz]` to the pip requirements
# string value is passed to dateutil.tz.gettz()
# leave blank for localtime
# timezone =
# max length of characters to apply to the
# "slug" field
# truncate_slug_length = 40
# set to 'true' to run the environment during
# the 'revision' command, regardless of autogenerate
# revision_environment = false
# set to 'true' to allow .pyc and .pyo files without
# a source .py file to be detected as revisions in the
# versions/ directory
# sourceless = false
# version location specification; This defaults
# to alembic/versions. When using multiple version
# directories, initial revisions must be specified with --version-path.
# The path separator used here should be the separator specified by "version_path_separator" below.
# version_locations = %(here)s/bar:%(here)s/bat:alembic/versions
# version path separator; As mentioned above, this is the character used to split
# version_locations. The default within new alembic.ini files is "os", which uses os.pathsep.
# If this key is omitted entirely, it falls back to the legacy behavior of splitting on spaces and/or commas.
# Valid values for version_path_separator are:
#
# version_path_separator = :
# version_path_separator = ;
# version_path_separator = space
version_path_separator = os # Use os.pathsep. Default configuration used for new projects.
# set to 'true' to search source files recursively
# in each "version_locations" directory
# new in Alembic version 1.10
# recursive_version_locations = false
# the output encoding used when revision files
# are written from script.py.mako
# output_encoding = utf-8
sqlalchemy.url =
[post_write_hooks]
# post_write_hooks defines scripts or Python functions that are run
# on newly generated revision scripts. See the documentation for further
# detail and examples
# format using "black" - use the console_scripts runner, against the "black" entrypoint
# hooks = black
# black.type = console_scripts
# black.entrypoint = black
# black.options = -l 79 REVISION_SCRIPT_FILENAME
# Logging configuration
[loggers]
keys = root,sqlalchemy,alembic
[handlers]
keys = console
[formatters]
keys = generic
[logger_root]
level = WARN
handlers = console
qualname =
[logger_sqlalchemy]
level = WARN
handlers =
qualname = sqlalchemy.engine
[logger_alembic]
level = INFO
handlers =
qualname = alembic
[handler_console]
class = StreamHandler
args = (sys.stderr,)
level = NOTSET
formatter = generic
[formatter_generic]
format = %(levelname)-5.5s [%(name)s] %(message)s
datefmt = %H:%M:%S
My main.py looks like this:
import uvicorn
from fastapi import FastAPI
import os
from fastapi_sqlalchemy import DBSessionMiddleware
from fastapi_sqlalchemy import db
from models import User as ModelUser
from schema import User as SchemaUser
from dotenv import load_dotenv
BASE_DIR = os.path.dirname(os.path.abspath(__file__))
load_dotenv(os.path.join(BASE_DIR, ".env"))
app = FastAPI()
app.add_middleware(DBSessionMiddleware, db_url=os.environ["OPERATIONAL_DATABASE_URL"])
@app.post("/user/", response_model=SchemaUser)
def create_user(user: SchemaUser):
db_user = ModelUser(
first_name=user.first_name, last_name=user.last_name, age=user.age
)
db.session.add(db_user)
db.session.commit()
return db_user
if __name__ == "__main__":
uvicorn.run(app, host="0.0.0.0", port=8000)
And finally I have a .env file with my db url:
OPERATIONAL_DATABASE_URL = postgresql+psycopg2://postgres:postgres@db:5432
The url points to a postgres docker container that has a database called "test_db", created with the following docker-compose code:
db:
image: postgres:11
ports:
- "5432:5432"
environment:
- POSTGRES_USER=postgres
- POSTGRES_PASSWORD=postgres
- POSTGRES_DB=test_db
When I create a revision with auto generate and then run a migration, the table is created in a database called "postgres", and I can't see where this is specified in the configuration. I would like to be able to choose which database is being targeted and update "test_db" but have only found configuration at the server level (the db url).
Any help would be much appreciated.
This:
OPERATIONAL_DATABASE_URL = postgresql+psycopg2://postgres:postgres@db:5432
is incomplete if you want to point at test_db.
To do that modify to:
OPERATIONAL_DATABASE_URL = postgresql+psycopg2://postgres:postgres@db:5432/test_db
See here Connection strings Section 34.1.1.2. Connection URIs. Without an explicit database name the database name used will be equal to the user name, in this case postgres per Connection keywords.