Post-deploy migrations exist to allow for seamless Discourse upgrades. By design, they cause migrations to run out of numerical order. This has the potential to cause some unexpected edge cases. To reduce the likelihood of these edge cases, we will promote historical post_deploy migrations to regular migrations after a full Discourse stable release cycle.
This script is intended to be run at least during every Discourse release cycle.
This means that truly seamless upgrades will not be possible between non-consecutive Discourse versions. (Upgrades will still work, but may cause some server errors for users during the upgrade)
David Taylor