amazing @mleczakm ! Could you please take a look at failing jobs?

oh I know what is wrong, you need to add MySQL to the testsuite workflow file as well, it's not using docker-compose https://github.com/flow-php/flow/blob/1.x/.github/workflows/test-suite.yml#L74

some tests are failing now :(

not sure if I fully get the tests part, but let me explain my reasoning behind Bulk::insert and Bulk::upsert.

• Bulk::insert - insert BulkData into given table, whenever records are already in that table, this operation should let us to update them (and here is where custom settings comes into play)
• Bulk::update - update data in table taking values from BulkData

The reason why I decide to go with $insertOptions that takes optional keys is because I wasn't able to find common parts between PostgreSQL and MySQL so I decided that each engine can define it's own keys and make the optional.
There is also Dialect, that should prepare the query and check if all needed options are provided.

And about the tests, you don't need to replicate all PostgreSQL tests, it would be enough to just test all options supported by MySQL. As long as insert can do upserts and update is only about updates it should be fine.

Thanks @mleczakm! I left two small comments but they are something that can be improved later, nothing critical, mostly code organization.