Refactor swh.core.db.pytest_plugin
update the postgresql_fact fixture to be able to use new-ish pytest_postgresql ability to recreate databases between tests from a template database.
The ides is to stop using the fragile and confusing "reset" of the database between tests, which means de facto keep a stateful database between tests, which make tests result depend on de facto order of execution of these tests.
For example, test_smoke_test_people_db_up_and_reset cannot be executed alone, since it depends on the fact test_smoke_test_people_db_up has been executed before so that the people's db has been reset as a result of the test setup done by the fixture, which will happen if and only if the database already exists (thus if another test using this db has been executed before in this test session).
The old table truncate based behavior has been kept (using a no_db_drop flag argument) in this diff for bw compatibility reasons, and also because the new drop-and-create-from-template beahvior remains a bit slower, which might be a problem for some test cases.
Tests for dependencies (swh-storage, etc.) should still pass with this refactoring, but will be significantly slower.
A series of revisions for these dependencies is about to be proposed to adapt them to the new db metadata (version, module, flavor) handling feature coming with swh.core 2, as well as updating their tests to take advantage of the template-based db creation in tests, which should bring back test execution time to almost the same as before this refactoring.
This is needed to be able to implement and test support for the new 'swh db upgrade' all this is actually about.
Depends on !317 (closed)
Migrated from D7155 (view on Phabricator)