issue_comments: 506784912

Documentation, to be added as a subsection of https://sqlite-utils.readthedocs.io/en/latest/python-api.html#adding-foreign-key-constraints

Adding multiple foreign key constraints at once

The final step in adding a new foreign key to a SQLite database is to run VACUUM, to ensure the new foreign key is available in future introspection queries.

VACUUM against a large (multi-GB) database can take several minutes or longer. If you are adding multiple foreign keys using table.add_foreign_key(...) these can quickly add up.

Instead, you can use db.add_foreign_keys(...) to add multiple foreign keys within a single transaction. This method takes a list of four-tuples, each one specifying a table, column, other_table and other_column.

Here's an example adding two foreign keys at once:

db.add_foreign_keys([
    ("dogs", "breed_id", "breeds", "id"),
    ("dogs", "home_town_id", "towns", "id")
])