Update v61 migration to handle duplicate job names before unique constraint

[collado-mike]

Problem

The v61 migration reapplies a unique constraint on job name and namespace without regard to parent job. Unfortunately, there are some cases when job FQNs are duplicated (mostly due to the issue fixed in #2097 , but also including cases when a job previously had no parent and now has a parent, but the same FQN). This update to the migration renames jobs that have been symlinked to point to newer versions of themselves so that the job FQN doesn't conflict and the unique constraint can be applied.

Any installations that have already applied this migration will not see any new operations on their data, but installations that have duplicates will need this fix for the migration to successfully complete.

I tested this on an installation with ~200,000 job names and was able to complete the migration successfully.

Checklist

• You've signed-off your work
• Your changes are accompanied by tests (if relevant)
• Your change contains a small diff and is self-contained
• You've updated any relevant documentation (if relevant)
• You've included a one-line summary of your change for the CHANGELOG.md (Depending on the change, this may not be necessary).
• You've versioned your .sql database schema migration according to Flyway's naming convention (if relevant)
• You've included a header in any source code files (if relevant)

[codecov]

Codecov Report

Merging #2464 (9912536) into main (3b0cde3) will not change coverage.
The diff coverage is n/a.

❗ Current head 9912536 differs from pull request most recent head 0ef8e13. Consider uploading reports for the commit 0ef8e13 to get more accurate results

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[wslulciuc]

This will set a job with a conflict to {job_name}_{row_num}?

[collado-mike]

Right, but row_number() over (PARTITION BY j.namespace_name, j.name ORDER BY j.created_at) AS row means that all jobs that have the same name will have an incrementing counter suffixed so we avoid the conflict. E.g., if we had three jobs with the FQN a.b, the names would be

1. a.b_1
2. a.b_2
3. a.b_3
   Thus, we can add the uniqueness constraint because they'll all end up with different names.

[wslulciuc]

Sweet, thanks for clarifying and the examples 👍

[wslulciuc]

Your writeup in the PR description was helpful in understanding all that's going on in the migration script. Thanks! And, also, 👍