Documentation Index
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Life Cost persists all financial data — wallets, transactions, categories, tags, and user accounts — in a MySQL 8.0 database. The application uses Flask-SQLAlchemy as its ORM and creates all required tables automatically the first time the server starts. No separate migration step is needed for a fresh installation.
Requirements
- MySQL 8.0 (or a compatible MariaDB version)
- The database and user must be created before starting the app
- The
mysqlclient Python package (included in requirements.txt) is used as the database driver
The easiest way to satisfy these requirements is with the bundled Docker Compose setup described at the bottom of this page.
The database connection is configured entirely through the DATABASE_URL environment variable. SQLAlchemy expects a URL in the following format:
mysql://user:password@host:port/dbname
| Segment | Description | Example |
|---|
user | MySQL username | admin |
password | MySQL password for that user | secret |
host | Hostname or IP of the MySQL server | localhost |
port | MySQL port (optional; defaults to 3306) | 3306 |
dbname | Name of the target database | life_db |
DATABASE_URL=mysql://admin:secret@localhost/life_db
Schema Overview
All tables are defined as SQLAlchemy models in app/models.py. The following tables are created automatically by db.create_all() on startup.
user
Stores authenticated user accounts. Populated on first Google sign-in.
| Column | Type | Notes |
|---|
id | Integer (PK) | Auto-increment primary key |
username | String(150) | Unique; synced from Google profile name |
email | String(150) | Unique; synced from Google account email |
picture | String(300) | URL of Google profile picture; nullable |
last_visited_wallet_id | Integer (FK) | Foreign key → wallet.id; nullable |
wallet
Represents a spending wallet (e.g., a budget or account).
| Column | Type | Notes |
|---|
id | Integer (PK) | Auto-increment primary key |
name | String(150) | Unique; required |
description | String(300) | Optional |
user_wallet
Many-to-many association table linking users to wallets. Every new wallet is automatically associated with all existing users.
| Column | Type | Notes |
|---|
user_id | Integer (PK/FK) | Foreign key → user.id |
wallet_id | Integer (PK/FK) | Foreign key → wallet.id |
created_at | DateTime | Defaults to UTC timestamp at insert |
category
Represents a spending category (tag label). Categories can be nested via category_parent.
| Column | Type | Notes |
|---|
id | Integer (PK) | Auto-increment primary key |
name | String(200) | Required |
category_parent | Integer | Optional self-reference to a parent category |
number_of_operation | Integer | Count of operations using this category |
money_transfer
The core financial record — a single income or expense entry.
| Column | Type | Notes |
|---|
id | Integer (PK) | Auto-increment primary key |
wallet_id | Integer | References wallet.id (no FK constraint at DB level) |
amount | Float | Positive = expense, negative = income; required |
description | String(200) | Free-text note; required |
created_at | DateTime | Defaults to UTC timestamp at insert |
modifed_at | DateTime | Defaults to UTC timestamp at insert; updated on edit |
user_id | Integer | References user.id (no FK constraint at DB level); required |
tag
Join table connecting a money_transfer record to one or more category entries.
| Column | Type | Notes |
|---|
id | Integer (PK) | Auto-increment primary key |
category_id | Integer (FK) | Foreign key → category.id |
money_transfer_id | Integer (FK) | Foreign key → money_transfer.id |
Automatic Table Creation
On every application startup, Flask-SQLAlchemy calls db.create_all() inside the app context:
with app.app_context():
db.create_all()
CREATE TABLE IF NOT EXISTS statements for any tables that do not yet exist. It is safe to run against an already-initialised database — existing tables and data are never touched.
db.create_all() does not run schema migrations. If you add a new column or change a column type in a model after the table has already been created, the change will not be applied automatically. You must either apply the change manually with raw SQL or introduce a migration tool such as Flask-Migrate / Alembic.-- Example: manually adding a column that was added to a model
ALTER TABLE money_transfer ADD COLUMN currency VARCHAR(10) DEFAULT 'USD';
Using the Bundled Docker MySQL
The docker-compose.yml file in the repository starts a MySQL 8.0 container alongside the application. The relevant portion of the file is:
services:
mysql:
image: mysql:8.0
container_name: mysql_container
environment:
MYSQL_ROOT_PASSWORD: Spigit123!
MYSQL_DATABASE: life_db
MYSQL_USER: admin
MYSQL_PASSWORD: 123
volumes:
- mysql_data:/var/lib/mysql
ports:
- "3306:3306"
phpmyadmin:
image: phpmyadmin/phpmyadmin
container_name: phpmyadmin
environment:
PMA_HOST: mysql_container
MYSQL_ROOT_PASSWORD: Spigit123!
ports:
- "8080:80"
depends_on:
- mysql
volumes:
mysql_data:
mysql_data, so data persists across container restarts.
After starting the MySQL container, verify connectivity before launching the app by running a simple liveness query:docker exec -it mysql_container mysql -u admin -p123 life_db -e "SELECT 1;"
1 confirms the server is reachable and the life_db database exists. If you are connecting from outside Docker, you can use any MySQL client:mysql -h 127.0.0.1 -P 3306 -u admin -p123 life_db -e "SELECT 1;"