Blacklist tables for add_column_with_default
What does this MR do?
We added a rubocop to warn about using add_column_with_default ... allow_nulls: false. This was meant to spark discussion about whether or not the table in question is potentially too large and if we would expect problems on large installations like GitLab.com.
However, I think it rather led to confusion and actually avoiding the helper all together (and finding more creative solutions to work around the cop ;) ). It is relatively safe to ignore the cop for small tables. Only for larger tables, we need to discuss in more detail during review.
I would like to turn the logic around and only trigger the warning for selected tables. Here, I've selected all tables from GitLab.com larger than 10 GB (also see Grafana):
In the longer term, the whole topic should go away with #207820 (closed).
Note we also have Migration/UpdateLargeTable which is related: In contrast to this cop, the cop we're changing here only cares about allow_null: false variants of the helper. This is because validating the NOT NULL constraint can take quite some time - in that sense, it's only tangentially related to the other cop.
Issue: #198351 (closed)