Run tests on MySQL 8 with MySQL8InnoDBDialect

[dennis-gr]

Run tests on MySQL 8 since 5.7 has reached EOL

[RogerKratz]

Thanks!
As you can see, MySQL step in pipe now fails. Can you have a look please?

[dennis-gr]

Should be fixed now.

[RogerKratz]

still seems to be failing

[dennis-gr]

Third time’s the charm ;-)

[RogerKratz]

Do you have any clue why mysqls tests are so much slower now?

[dennis-gr]

It's most likely due to the schema creation being slower with MySQL 8 than 5.7. I did some measurements on a another project I'm working on, and the ALTER TABLE statements for foreign key creation made up about 80% of the total time spend on schema creation.

I've added another commit to put the data dir in tmpfs, which should speed up things a bit.

[dennis-gr]

@RogerKratz Anything else preventing you from merging this? There's unfortunately nothing more that can be done to speed up the tests (see the discussion here for example).
If the test runtime is an issue for you, I could prepare another PR that uses MariaDB where schema creation performance is much better.

[RogerKratz]

thanks! squashed and rebased