Module to manage people in a system.

It uses a base person class along with specialized people.

• Create a virtualenv
• Run pip install -r requirements.txt
• Set environment variables: FLASK_APP=people.py SQLALCHEMY_URI=<your database connection string> SQLALCHEMY_DATABASE_URI=SQLALCHEMY_URI USPS_USERID="<USPS User Id>"
• Set GRAPHIQL=true, if you wish to use the 'GraphiQL' interface.

Two additional, flask commands exist for prepping the database.

• initdb creates the table schema for the application. Shouldn't be needed. flask db upgrade should be used instead.

• seed populates the database with data found in the directory specified. DEMO loads demo data. It's not intended to do updates, only initial data load. Usage: flask seed {load files directory} (defaults to 'seed') {demo switch} (defaults to 'false').

You should be able to access the graphql console via http://127.0.0.1:5000/graphql

If the system reports

Usage: flask [OPTIONS] COMMAND [ARGS]...
Try "flask --help" for help.

Error: No such command "command".

when executing some commands then confirm you set FLASK_APP=people.py.

This section manages the database. It's primary focus is SqlAlchmey models used by other scripts. Additionally, it houses the migration scripts used for managing the database schema.

NOTE: The database is geared for Postgresql. It hasn't been tested with other database server types.

models.py describes the tables using SqlAlchemy.

migrations directory holds the migrations scripts.

alembic.ini configures the migration process. There's a copy of this file in ../migrations_config if you need to redo the migrations process.

functions directory contains Postgres function code.

views directory contains Postgres view code.

flask db, 'Alembic under the covers', is used for database migrations; making changes to tables.

Alembic is configured to generate migration files from changes to models.py. Manual modifications can be accomplished by manually changing the generated files.

3. Set SQLALCHEMY_DATABASE_URI to point to the proper database.

4. Run flask db migrate -m "<some comment>" to generate a new 'version' file within the 'versions' directory.

5. Check the migrations directory for a file matching your comment. Confirm the file has the expected changes. If not, you'll need to modify it so it aligns with the model changes you made earlier.

6. Run flask db upgrade to apply all version files.

Important Note: Migration must occur prior to 'seeding the database.

Run flask db upgrade followed by flask seed.

This section is dedicated to the problems and subsequent solutions encountered while working on the code.

Problem

(.env)% alembic revision --autogenerate -m "Create New Table"
INFO  [alembic.runtime.migration] Context impl SQLiteImpl.
INFO  [alembic.runtime.migration] Will assume non-transactional DDL.
ERROR [alembic.util.messaging] Target database is not up to date.
  FAILED: Target database is not up to date.

Solution

The migration script can't connect to a database. Make sure the environment variable, SQLALCHEMY_URI is set to the proper database.

Problem

The command alembic revision <command> results in ...

  File "<frozen importlib._bootstrap_external>", line 728, in exec_module
  File "<frozen importlib._bootstrap>", line 219, in _call_with_frames_removed
  File "migrations/env.py", line 11, in <module>
    from database import models
ModuleNotFoundError: No module named 'database'

Solution

PYTHONPATH isn't set correctly. Set it to point to the root of the workspace.

Problem

Running alembic command results in FAILED: No config file 'alembic.ini' found, or file has no '[alembic]' section

Solution

Change to the app directory and rerun the command.

Problem

The command alembic revision --autogenerate -m "some comment" returns

  File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/configparser.py", line 1197, in set
    self._validate_value_types(option=option, value=value)
  File "/Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/configparser.py", line 1182, in _validate_value_types
    raise TypeError("option values must be strings")
TypeError: option values must be strings

Solution

Make sure the environment variable, SQLALCHEMY_URI is set to the proper database.

Problem

Executing alembic upgrade head results in an error. For example:

  File "/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/site-packages/sqlalchemy/util/compat.py", line 207, in raise_
    raise exception
  File "/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/site-packages/sqlalchemy/engine/base.py", line 1771, in _execute_context
    self.dialect.do_execute(
  File "/Library/Frameworks/Python.framework/Versions/3.9/lib/python3.9/site-packages/sqlalchemy/engine/default.py", line 717, in do_execute
    cursor.execute(statement, parameters)
sqlalchemy.exc.InternalError: (psycopg2.errors.DependentObjectsStillExist) cannot drop view pg_stat_statements because extension pg_stat_statements requires it
HINT:  You can drop extension pg_stat_statements instead.

Solution

Troubleshoot as you would a Python program. In this is was a matter of removing a step in the migration script. That's why the migration output includes a line, # ### commands auto generated by Alembic - please adjust! ###