eralchemy2 1.4.1
Simple entity relation (ER) diagrams generation
License: Apache-2.0
Requires Python: >=3.8
Keywords: sql, ORM, relational databases, ER diagram, render


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# Entity relation diagrams generator

eralchemy2 generates Entity Relation (ER) diagram (like the one below) from databases or from SQLAlchemy models.
Works with SQLAlchemy < 1.4 but also with versions greater than 1.4

## Example

![Example for a graph](https://raw.githubusercontent.com/maurerle/eralchemy2/main/newsmeme.svg?raw=true "Example for NewsMeme")

[Example for NewsMeme](https://bitbucket.org/danjac/newsmeme)

## Quick Start

### Install
To install eralchemy2, just do:

    $ pip install eralchemy2

`eralchemy2` requires [GraphViz](http://www.graphviz.org/download) to generate the graphs and Python. Both are available for Windows, Mac and Linux.

For Debian based systems, run:

    $ apt install graphviz libgraphviz-dev

before installing eralchemy2.

### Install using conda

There is also a packaged version in conda-forge, which directly installs the dependencies:

    $ conda install -c conda-forge eralchemy2

### Usage from Command Line

#### From a database

    $ eralchemy2 -i sqlite:///relative/path/to/db.db -o erd_from_sqlite.pdf

The database is specified as a [SQLAlchemy](https://docs.sqlalchemy.org/en/20/core/engines.html#database-urls)
database url.

#### From a markdown file.

    $ curl 'https://raw.githubusercontent.com/maurerle/eralchemy2/main/example/newsmeme.er' > markdown_file.er
    $ eralchemy2 -i 'markdown_file.er' -o erd_from_markdown_file.pdf

#### From a Postgresql DB to a markdown file excluding tables named `temp` and `audit`

    $ eralchemy2 -i 'postgresql+psycopg2://username:password@hostname:5432/databasename' -o filtered.er --exclude-tables temp audit

#### From a Postgresql DB to a markdown file excluding columns named `created_at` and `updated_at` from all tables

    $ eralchemy2 -i 'postgresql+psycopg2://username:password@hostname:5432/databasename' -o filtered.er --exclude-columns created_at updated_at

#### From a Postgresql DB to a markdown file for the schemas `schema1` and `schema2`

    $ eralchemy2 -i 'postgresql+psycopg2://username:password@hostname:5432/databasename' -s "schema1, schema2"

#### Specify Output Mode

    $ eralchemy2 -i 'markdown_file.er' -o erd_from_markdown_file.md -m mermaid_er

### Usage from Python

```python
from eralchemy2 import render_er
## Draw from SQLAlchemy base
render_er(Base, 'erd_from_sqlalchemy.png')

## Draw from database
render_er("sqlite:///relative/path/to/db.db", 'erd_from_sqlite.png')
```

## Architecture
![Architecture schema](https://raw.githubusercontent.com/maurerle/eralchemy2/main/eralchemy_architecture.png?raw=true "Architecture schema")

Thanks to it's modular architecture, it can be connected to other ORMs/ODMs/OGMs/O*Ms.

## Contribute

Every feedback is welcome on the [GitHub issues](https://github.com/maurerle/eralchemy2/issues).

### Development

Install the development dependencies using

    $ pip install -e .[ci,dev]

Make sure to run the pre-commit to fix formatting

    $ pre-commit run --all

All tested PR are welcome.

## Running tests

This project uses the pytest test suite.
To run the tests, use : `$ pytest` or `$ tox`.

Some tests require having a local PostgreSQL database with a schema named test in a database
named test all owned by a user named eralchemy with a password of eralchemy.
If docker compose is available, one can use `docker compose up -d` for this purpose.
You can deselct the tests which require a PostgreSQL database using:

    $ pytest -m "not external_db"

## Publishing a release

    $ rm -r dist && python -m build && python3 -m twine upload --repository pypi dist/*

## Notes

eralchemy2 is a fork of its predecessor [ERAlchemy](https://github.com/Alexis-benoist/eralchemy) by @Alexis-benoist, which is not maintained anymore and does not work with SQLAlchemy > 1.4.
If it is maintained again, I'd like to push the integrated changes upstream.

ERAlchemy was inspired by [erd](https://github.com/BurntSushi/erd), though it is able to render the ER diagram directly
from the database and not just only from the `ER` markup language.

Released under an Apache License 2.0

Initial Creator: Alexis Benoist [Alexis_Benoist](https://github.com/Alexis-benoist)