SQLite: Foreign Key "ON DELETE SET NULL" action not getting triggered - sql

Question

Why is ON DELETE SET NULL failing when deleting a row via the application code, but it behaves correctly when manually executing an SQL statement?
I have a todo table and a category table. The todo table has a category_id foreign key that references id in the category table, and it was created with the "ON DELETE SET NULL" action.
create table `category` (
`id` integer not null primary key autoincrement,
`name` varchar(255) not null
);
create table `todo` (
`id` integer not null primary key autoincrement,
`title` varchar(255) not null,
`complete` boolean not null default '0',
`category_id` integer,
foreign key(`category_id`) references `category`(`id`) on delete SET NULL on update CASCADE
);
I also have an endpoint in my application that allows users to delete a category.
categoryRouter.delete('/:id', async (req, res) => {
const { id } = req.params
await req.context.models.Category.delete(id)
return res.status(204).json()
})
This route successfully deletes categories, but the problem is that related todo items are not getting their category_id property set to null, so they end up with a category id that no longer exists. Strangely though, if I open up my database GUI and manually execute the query to delete a category... DELETE FROM category WHERE id=1... the "ON DELETE SET NULL" hook is successfully firing. Any todo item that had category_id=1 is now set to null.
Full application source can be found here.

Answer 1

Figured it out, thanks to MikeT.
So apparently SQLite by default has foreign key support turned off. WTF!
To enable FKs, I had to change my code from this...
const knex = Knex(knexConfig.development)
Model.knex(knex)
to this...
const knex = Knex(knexConfig.development)
knex.client.pool.on('createSuccess', (eventId, resource) => {
resource.run('PRAGMA foreign_keys = ON', () => {})
})
Model.knex(knex)
Alternatively, I could have done this inside of the knexfile.js...
module.exports = {
development: {
client: 'sqlite3',
connection: {
filename: './db.sqlite3'
},
pool: {
afterCreate: (conn, cb) => {
conn.run('PRAGMA foreign_keys = ON', cb)
}
}
},
staging: {},
production: {}
}

Answer 2

FYI and other people who stumbled across a similar problem, you need PRAGMA foreign_keys = ON not only for the child table but also for the parent table.
When I set PRAGMA foreign_keys = ON only for a program which handles the child table, ON UPDATE CASCADE was enabled but ON DELETE SET NULL was still disabled. At last I found out that I forgot PRAGMA foreign_keys = ON for another program which handles the parent table.