Handle error ERROR 70100 (1317): foreign key constraints are not allowed, see https://code.openark.org/blog/mysql/the-problem-with-mysql-foreign-key-constraints-in-online-schema-changes

[janpio]

PlanetScale or Vitess (with foreign_key_mode=disallow) throws the following error if you try to create a foreign key:

Error: Database error
Error querying the database: Server error: `ERROR 70100 (1317): foreign key constraints are not allowed, see https://code.openark.org/blog/mysql/the-problem-with-mysql-foreign-key-constraints-in-online-schema-changes'
   0: sql_migration_connector::sql_database_step_applier::apply_migration
             at migration-engine\connectors\sql-migration-connector\src\sql_database_step_applier.rs:15
   1: migration_core::api::SchemaPush
             at migration-engine\core\src\api.rs:163

To reproduce: Run a DDL statement that creates a foreign key on a non production branch (created via UI) on a PlanetScale database.

We should catch this and output a known error message with the following message text:

Foreign keys can not be created on this database. Learn more how to handle this: https://pris.ly/d/migrate-no-foreign-keys

(The link currently points to a rather general issue, but will be updated to point to a specific issue or documentation later)

The Vitess instances we are testing against do not show this behavior by default yet, but can be configured to do so via FOREIGN_KEY_MODE: disallow in docker-compose.yml. (Outstanding PR at prisma/prisma-engines#1958)

[janpio]

I think this works:

C:\Users\Jan\Documents\throwaway\pscaleMigrationTable>npx prisma migrate dev
Environment variables loaded from .env
Prisma schema loaded from prisma\schema.prisma
Datasource "db": MySQL database "migration-table-3" at "127.0.0.1:56287"

Error: P3006

Migration `20210709232641_bar` failed to apply cleanly to the shadow database. 
Error code: P3018
Error:
A migration failed to apply. New migrations cannot be applied before the error is recovered from. Read more about how to resolve migration issues in a production database: https://pris.ly/d/migrate-resolve

Migration name: 20210709232641_bar

Database error code: 1317

Database error:
Foreign keys cannot be created on this database. Learn more how to handle this: https://pris.ly/d/migrate-no-foreign-keys

Please check the query number 2 from the migration file.

A direct reference to the migration sql file would be nice here, but that is unrelated.