# Python ERD Generator from Postgres schema dump file

pypgsvg is an open source Python application that parses postgresql schema SQL dump files and generates 
Directed Entity Relationship Diagrams (Diagraph, ERDs) using Graphviz.  In a past life I had been tasked
with showing what the normalized postgresql database looks like for employers who do not want to pay for 
postgres tools that have the graphical tools. There are some free ones out there but requires the installation of Java, 
and does work well for what I needed it for, so admittedly this started as an academic excersise. By no 
means is this even an alledgedly full throated tool, but is being adapted to take all diagraph  args shortly as to 
offer some options for best display of the ERD. Some versions of this saved me hours of time in explainations, 
now easier to share.


```
 PYTHONPATH=src python -m pytest tests/tests/ 
 python -m src.pypgsvg Samples/schema.dump --output=test
```



## BETA, TODO, and Features
- TODO: Allow all argument options for Diagraph..
  - allow show/hide FK based on cascade type. 
  - CSS facelift.
- Parse PostgreSQL dump files to extract table definitions and relationships
- Generate interactive SVG Entity Relationship Diagrams
- Automatic color coding for tables with accessible color palette
- Support for complex SQL structures including foreign keys, constraints, and various data types
- Table filtering to exclude temporary/utility tables
- Comprehensive test suite with >90% code coverage

## Installation

1. Install pypgsvg:

```bash
pip install .
```

2. Ensure Graphviz is installed on your system:
   - **macOS**: `brew install graphviz`
   - **Ubuntu/Debian**: `sudo apt-get install graphviz`
   - **Windows**: Download from <https://graphviz.org/download/>

## Usage

### Basic Usage

Generate an ERD from your SQL dump file:

```bash
pypgsvg your_database.sql
```

This will create an SVG file with the same name as your input file (e.g., `your_database_erd.svg`).

### Example Output

Here's an example of the generated ERD from a sample database schema with users, posts, and comments:

[![Sample ERD](Samples/sample_schema_erd.svg)](Samples/sample_schema_erd.svg)

*Simple Blog Schema - showing basic relationships between users, posts, and comments*

---

For more complex databases, pypgsvg can handle extensive schemas with many tables and relationships:

[![Complex Database Schema](Samples/example.png)](Samples/schema_erd.svg)

*Complex Database Schema - demonstrating pypgsvg's ability to visualize large, real-world database structures*

*View the interactive SVG diagrams:*

- [Simple Schema Example](Samples/sample_schema_erd.svg)
- [Complex Database Schema Example](Samples/schema_erd.svg)

The diagram shows:

- **Tables** as nodes with their column definitions
- **Foreign key relationships** as directed edges between tables
- **Automatic color coding** for visual distinction
- **Accessible color palette** with proper contrast for readability

### Usage

Specify a custom output filename:

```bash
pypgsvg your_database_dump.sql --output custom_diagram.svg
```

View the diagram immediately after generation:

```bash
pypgsvg your_database_dump.sql --view
```

### Python API Usage

For programmatic use:

```python
from src.pypgsvg import parse_sql_dump, generate_erd_with_graphviz

# Load SQL dump
with open("your_database_dump.sql", "r", encoding='utf-8') as file:
    sql_content = file.read()

# Parse tables and relationships
tables, foreign_keys, errors = parse_sql_dump(sql_content)

# Generate ERD
if not errors:
    generate_erd_with_graphviz(tables, foreign_keys, "database_diagram")
    print("ERD generated successfully!")
else:
    print("Parsing errors found:", errors)
```

## Testing

Run the complete test suite with coverage:

```bash
# Run all tests with coverage
PYTHONPATH=src python -m pytest tests/tests/


# Run specific test categories
pytest -m unit          # Unit tests only
pytest -m integration   # Integration tests only

# Run with verbose output
pytest -v

# Generate HTML coverage report
pytest --cov-report=html
open htmlcov/index.html  # View coverage report
```

## Project Structure

```text
├── src/
│   └── create_graph.py          # Main application code
├── tests/
│   ├── conftest.py              # Test fixtures and configuration
│   ├── test_utils.py            # Tests for utility functions
│   ├── test_parser.py           # Tests for SQL parsing
│   ├── test_erd_generation.py   # Tests for ERD generation
│   └── test_integration.py      # Integration tests
├── requirements.txt             # Python dependencies
├── pyproject.toml              # pytest configuration
└── README.md                   # This file
```

## Configuration

### Table Exclusion

The application automatically excludes tables matching certain patterns (defined in `should_exclude_table`):

- Views (`vw_`)
- Backup tables (`bk`)
- Temporary fix tables (`fix`)
- Duplicate tables (`dups`, `duplicates`)
- Match tables (`matches`)
- Version logs (`versionlog`)
- Old tables (`old`)
- Member data (`memberdata`)

### Color Palette

The ERD uses an accessible color palette with automatic contrast calculation for text readability following WCAG guidelines.

## Supported SQL Features

- `CREATE TABLE` statements with various column types
- `CREATE TABLE IF NOT EXISTS`
- `ALTER TABLE ... ADD CONSTRAINT ... FOREIGN KEY`
- Quoted identifiers
- Complex data types (numeric, timestamp, jsonb, etc.)
- Multiple constraint variations

## Error Handling

The application includes comprehensive error handling for:

- Malformed SQL syntax
- Missing table references in foreign keys
- Unicode encoding issues
- File reading errors

## Contributing

1. Follow PEP 8 style guidelines
2. Write tests for new functionality
3. Maintain >90% test coverage
4. Use type hints where appropriate
5. Update documentation as needed

## Dependencies

- `graphviz>=0.20.1` - For generating diagrams
- `pytest>=7.4.0` - Testing framework
- `pytest-cov>=4.1.0` - Coverage reporting
- `pytest-mock>=3.11.0` - Mocking utilities
