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This is a tool that reads the structure of an existing database and generates the appropriate SQLAlchemy model code, using the declarative style if possible.

This tool was written as a replacement for sqlautocode_, which was suffering from several issues (including, but not limited to, incompatibility with Python 3 and the latest SQLAlchemy version).

.. _sqlautocode: http://code.google.com/p/sqlautocode/

Features

• Supports SQLAlchemy 2.x
• Produces declarative code that almost looks like it was hand written
• Produces PEP 8_ compliant code
• Accurately determines relationships, including many-to-many, one-to-one
• Automatically detects joined table inheritance
• Excellent test coverage

.. _PEP 8: http://www.python.org/dev/peps/pep-0008/

Installation

To install, do::

pip install sqlacodegen

To include support for the PostgreSQL CITEXT extension type (which should be considered as tested only under a few environments) specify the citext extra::

pip install sqlacodegen[citext]

To include support for the PostgreSQL GEOMETRY, GEOGRAPHY, and RASTER types (which should be considered as tested only under a few environments) specify the geoalchemy2 extra:

To include support for the PostgreSQL PGVECTOR extension type, specify the pgvector extra::

pip install sqlacodegen[pgvector]

.. code-block:: bash

pip install sqlacodegen[geoalchemy2]

Quickstart

At the minimum, you have to give sqlacodegen a database URL. The URL is passed directly to SQLAlchemy's create_engine()_ method so please refer to SQLAlchemy's documentation_ for instructions on how to construct a proper URL.

Examples::

sqlacodegen postgresql:///some_local_db
sqlacodegen --generator tables mysql+pymysql://user:password@localhost/dbname
sqlacodegen --generator dataclasses sqlite:///database.db
# --engine-arg values are parsed with ast.literal_eval
sqlacodegen oracle+oracledb://user:[email protected]:1521/XE --engine-arg thick_mode=True
sqlacodegen oracle+oracledb://user:[email protected]:1521/XE --engine-arg thick_mode=True --engine-arg connect_args='{"user": "user", "dsn": "..."}'

To see the list of generic options::

sqlacodegen --help

.. _create_engine(): http://docs.sqlalchemy.org/en/latest/core/engines.html#sqlalchemy.create_engine .. _SQLAlchemy's documentation: http://docs.sqlalchemy.org/en/latest/core/engines.html

Available generators

The selection of a generator determines the

The following built-in generators are available:

• tables (only generates Table objects, for those who don't want to use the ORM)
• declarative (the default; generates classes inheriting from declarative_base()
• dataclasses (generates dataclass-based models; v1.4+ only)
• sqlmodels (generates model classes for SQLModel_)

.. _SQLModel: https://sqlmodel.tiangolo.com/

Generator-specific options

The following options can be turned on by passing them using --options (multiple values must be delimited by commas, e.g. --options noconstraints,nobidi):

• tables

  • noconstraints: ignore constraints (foreign key, unique etc.)
  • nocomments: ignore table/column comments
  • noindexes: ignore indexes
  • nonativeenums: don't generate Python enum classes for native database ENUM types (e.g., PostgreSQL ENUM); use plain string mapping instead
  • nosyntheticenums: don't generate Python enum classes from CHECK constraints with IN clauses (e.g., column IN ('value1', 'value2', ...)); preserves CHECK constraints as-is
  • noidsuffix: prevent the special naming logic for single column many-to-one and one-to-one relationships (see Relationship naming logic_ for details)
  • include_dialect_options: render a table' dialect options, such as starrocks_partition for StarRocks' specific options.
  • keep_dialect_types: preserve dialect-specific column types instead of adapting to generic SQLAlchemy types.

• declarative

  • all the options from tables
  • use_inflect: use the inflect library when naming classes and relationships (turning plural names into singular; see below for details)
  • nojoined: don't try to detect joined-class inheritance (see below for details)
  • nobidi: generate relationships in a unidirectional fashion, so only the many-to-one or first side of many-to-many relationships gets a relationship attribute, as on v2.X
  • nofknames: disable improved relationship naming when multiple FKs or junction tables connect to the same target. By default, uses FK column names for one-to-many (e.g., simple_items_parent_container) and junction table names for many-to-many (e.g., students_enrollments). Reverts to underscore suffixes (simple_items_, student_).

• dataclasses

  • all the options from declarative

• sqlmodels

  • all the options from declarative
  • nolinktables: don't render many-to-many association tables as link model classes (Relationship(link_model=...)); render them as plain Table objects referenced via secondary instead

Model class generators

The code generators that generate classes try to generate model classes whenever possible. There are two circumstances in which a Table is generated instead:

• the table has no primary key constraint (which is required by SQLAlchemy for every model class)
• the table is an association table between two other tables (see below for the specifics)

Model class naming logic ++++++++++++++++++++++++

By default, table names are converted to valid PEP 8 compliant class names by replacing all characters unsuitable for Python identifiers with _. Then, each valid parts (separated by underscores) are title cased and then joined together, eliminating the underscores. So, example_name becomes ExampleName.

If the use_inflect option is used, the table name (which is assumed to be in English) is converted to singular form using the "inflect" library. For example, sales_invoices becomes SalesInvoice. Since table names are not always in English, and the inflection process is far from perfect, inflection is disabled by default.

Relationship detection logic ++++++++++++++++++++++++++++

Relationships are detected based on existing foreign key constraints as follows:

• many-to-one: a foreign key constraint exists on the table
• one-to-one: same as many-to-one, but a unique constraint exists on the column(s) involved
• many-to-many: an association table is found to exist between two tables (the sqlmodels generator renders association tables that have a primary key as link model classes, passed to the relationships via link_model=)

A table is considered an association table if it satisfies all of the following conditions:

#. has exactly two foreign key constraints #. all its columns are involved in said constraints

Relationship naming logic +++++++++++++++++++++++++

Relationships are typically named based on the table name of the opposite class. For example, if a class has a relationship to another class with the table named companies, the relationship would be named companies (unless the use_inflect option was enabled, in which case it would be named company in the case of a many-to-one or one-to-one relationship).

A special case for single column many-to-one and one-to-one relationships, however, is if the column is named like employer_id. Then the relationship is named employer due to that _id suffix.

For self referential relationships, the reverse side of the relationship will be named with the _reverse suffix appended to it.

When multiple foreign keys or junction tables connect to the same target table, relationships use qualifiers for disambiguation. One-to-many relationships use FK column names (e.g., simple_items_parent_container, simple_items_top_container). Many-to-many relationships use junction table names (e.g., students_enrollments, students_waitlist), except for self-referential cases which use FK column names (e.g., parent, child). The nofknames option reverts to underscore suffixes (simple_items_, student_).

Customizing code generation logic

If the built-in generators with all their options don't quite do what you want, you can customize the logic by subclassing one of the existing code generator classes. Override whichever methods you need, and then add an entry point_ in the sqlacodegen.generators namespace that points to your new class. Once the entry point is in place (you typically have to install the project with pip install), you can use --generator <yourentrypoint> to invoke your custom code generator.

For examples, you can look at sqlacodegen's own entry points in its pyproject.toml_.

.. _entry point: https://setuptools.readthedocs.io/en/latest/userguide/entry_point.html .. _pyproject.toml: https://github.com/agronholm/sqlacodegen/blob/master/pyproject.toml

Getting help

If you have problems or other questions, you should start a discussion on the sqlacodegen discussion forum. As an alternative, you could also try your luck on the sqlalchemy room on Gitter.

.. _sqlacodegen discussion forum: https://github.com/agronholm/sqlacodegen/discussions/categories/q-a .. _sqlalchemy: https://app.gitter.im/#/room/#sqlalchemy_community:gitter.im

Security contact information

To report a security vulnerability, please use the Tidelift security contact_. Tidelift will coordinate the fix and disclosure.

.. _Tidelift security contact: https://tidelift.com/security