Are there techniques to write the above in compatible ways? For example: "replace mod with % operator", can a shim "mod" function be implemented on Postgres?

Are there techniques to write the above in compatible ways? For example: "replace mod with % operator", can a shim "mod" function be implemented on Postgres? Do you think it's reasonable to lint/test your way to compatibility before transition, and then remove transitional code afterwards, or do you think it needs to be a long running fork of the codebase? We did the former for our Python 2-3 migration and it worked really well.