sqlalchemy_schemadisplay

Turn SQLAlchemy DB Model into a graph.

See SQLAlchemy wiki for the previous version of this doc.

Usage

You will need atleast SQLAlchemy and pydot along with graphviz for this. Graphviz-cairo is highly recommended to get tolerable image quality. If PIL and an image viewer are available then there are functions to automatically show the image. Some of the stuff, specifically loading list of tables from a database via a mapper and reflecting indexes currently only work on postgres.

This is an example of database entity diagram generation:

from sqlalchemy import MetaData, create_engine
from sqlalchemy_schemadisplay import create_schema_graph

# create the pydot graph object by autoloading all tables via a bound metadata object
graph = create_schema_graph(
   engine=create_engine('postgresql+psycopg2://user:pwd@host/database'),
   metadata=MetaData('postgres://user:pwd@host/database'),
   show_datatypes=False, # The image would get nasty big if we'd show the datatypes
   show_indexes=False, # ditto for indexes
   rankdir='LR', # From left to right (instead of top to bottom)
   concentrate=False # Don't try to join the relation lines together
)
graph.write_png('dbschema.png') # write out the file

And an UML class diagram from a model:

from myapp import model
from sqlalchemy_schemadisplay import create_uml_graph
from sqlalchemy.orm import class_mapper

# lets find all the mappers in our model
mappers = [model.__mapper__]
for attr in dir(model):
    if attr[0] == '_': continue
    try:
        cls = getattr(model, attr)
        mappers.append(cls.property.entity)
    except:
        pass

# pass them to the function and set some formatting options
graph = create_uml_graph(mappers,
    show_operations=False, # not necessary in this case
    show_multiplicity_one=False # some people like to see the ones, some don't
)
graph.write_png('schema.png') # write out the file

Changelog

2.0 - 2024-02-15

• Compatibility with SQLAlchemy 2.x [Jonathan Chico]
• Python requirements changed to >= 3.8 [zlopez]

1.4 - 2024-02-15

Last release to support Python 2.

• Limit SQLAlchemy dependency to < 2.0 to fix installation for Python 2 [abitrolly - Anatoli Babenia]
• Set dir kwarg in Edge instantiation to 'both' in order to show arrow heads and arrow tails. [bkrn - Aaron Di Silvestro]
• Add 'show_column_keys' kwarg to 'create_schema_graph' to allow a PK/FK suffix to be added to columns that are primary keys/foreign keys respectively [cchrysostomou - Constantine Chrysostomou]
• Add 'restrict_tables' kwarg to 'create_schema_graph' to restrict the desired tables we want to generate via graphviz and show relationships for [cchrysostomou - Constantine Chrysostomou]

1.3 - 2016-01-27

• Fix warning about illegal attribute in uml generation by using correct attribute. [electrocucaracha - Victor Morales]
• Use MIT license [fschulze]

1.2 - 2014-03-02

• Compatibility with SQLAlchemy 0.9. [fschulze]
• Compatibility with SQLAlchemy 0.8. [Surgo - Kosei Kitahara]
• Leave tables out even when a foreign key points to them but they are not in the table list. [tiagosab - Tiago Saboga]

1.1 - 2011-10-12

• New option to skip inherited attributes. [nouri]
• Quote class name, because some names like 'Node' confuse dot. [nouri - Daniel Nouri]

1.0 - 2011-01-07

• Initial release [fschulze - Florian Schulze]
• Original releases as recipe on SQLAlchemy Wiki by Ants Aasma