Foreign Key creation with SQLite

[Mavv3006]

Hi everyone,

I have a question about the foreign key index generation during database migrations because I noticed some strange behaviour.

Question: Are the foreign key indices during database migration only created when the database table has not been created yet, so only during the create table SQL command?

Background:
I have a table called setlist_entries which currently has the following columns: id, song_id (foreign key to the songs table), sequence_number. What I want to do is to alter this table and add a foreign key constrained to the concerts table (which has an id as primary key). The issue I am facing currently is that $table->foreignId('concert_id')->constrained('concerts'); is only generating this SQL: alter table "setlist_entries" add column "concert_id" integer not null, but no foreign key constrained (or index). Am I doing something wrong, or is Laravel just behaving this way, that foreign key constraines are only evaluated and created during initial database table generation?

Update:
See https://github.com/Mavv3006/db-foreign-key-test as a reference.

Steps to reproduce (use sqlite database):

1. run all migrations with php artisan migrate
2. reroll last migration with php artisan migrate:rollback --step=1
3. look at the SQL for the last migration with php artisan migrate --pretend

This is what the console output looks like:

[Mavv3006]

I found my answer in this Stackoverflow answer: https://stackoverflow.com/a/1884841/13791215