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table.foreign_keys now handles compound foreign keys, refs #594

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This is a breaking change, since the return type is now a dataclass
and not a namedtuple.
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Simon Willison 2026-07-05 13:59:25 -07:00
commit f10459cffb
5 changed files with 232 additions and 36 deletions
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docs/python-api.rst
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@ -2204,17 +2204,35 @@ Almost all SQLite tables have a ``rowid`` column, but a table with no explicitly
.foreign_keys
-------------
The ``.foreign_keys`` property returns any foreign key relationships for the table, as a list of ``ForeignKey(table, column, other_table, other_column)`` named tuples. It is not available on views.
The ``.foreign_keys`` property returns any foreign key relationships for the table, as a list of ``ForeignKey`` objects. It is not available on views.
Each ``ForeignKey`` has the following attributes:
``table``
The table the foreign key is defined on.
``column``
The column on this table, or ``None`` for a compound foreign key.
``other_table``
The table being referenced.
``other_column``
The referenced column, or ``None`` for a compound foreign key.
``columns``
A list of the columns on this table, always populated (a single-item list for single-column foreign keys).
``other_columns``
A list of the referenced columns.
``is_compound``
``True`` if this is a compound (multi-column) foreign key.
``ForeignKey`` was a ``namedtuple`` prior to sqlite-utils 4.0. It is now a dataclass and can no longer be unpacked or indexed as a tuple - access its fields by name instead. See :ref:`upgrading_3_to_4` for details.
::
>>> db.table("Street_Tree_List").foreign_keys
[ForeignKey(table='Street_Tree_List', column='qLegalStatus', other_table='qLegalStatus', other_column='id'),
ForeignKey(table='Street_Tree_List', column='qCareAssistant', other_table='qCareAssistant', other_column='id'),
ForeignKey(table='Street_Tree_List', column='qSiteInfo', other_table='qSiteInfo', other_column='id'),
ForeignKey(table='Street_Tree_List', column='qSpecies', other_table='qSpecies', other_column='id'),
ForeignKey(table='Street_Tree_List', column='qCaretaker', other_table='qCaretaker', other_column='id'),
ForeignKey(table='Street_Tree_List', column='PlantType', other_table='PlantType', other_column='id')]
[ForeignKey(table='Street_Tree_List', column='qLegalStatus', other_table='qLegalStatus', other_column='id', columns=['qLegalStatus'], other_columns=['id'], is_compound=False),
ForeignKey(table='Street_Tree_List', column='qCareAssistant', other_table='qCareAssistant', other_column='id', columns=['qCareAssistant'], other_columns=['id'], is_compound=False),
...]
Compound foreign keys - defined with ``FOREIGN KEY (col_a, col_b) REFERENCES other(col_a, col_b)`` - are returned as a single ``ForeignKey`` with ``is_compound=True``, ``column`` and ``other_column`` set to ``None``, and the participating columns available in the ``columns`` and ``other_columns`` lists.
.. _python_api_introspection_schema: