Ruby on Rails / PostgreSQL Version Compatibility

[Don P]

I am currently upgrading a few Rails apps from 4.1.8 up the ladder to Rails 6 and finding some difficulty understanding which version of the `pg` gem should work with the various Rails and PostgreSQL versions.  Some issues: 

1. ActiveRecord::StatementInvalid (PG::UndefinedColumn: ERROR:  column "increment_by" does not exist  , pg gem version 0.21, PostgreSQL 10.  Which version of the gem supports later versions of PostgreSQL? 
2. If I upgrade to pg > 1.0.0, I get a different error: Specified 'postgresql' for database adapter, but the gem is not loaded. Add `gem 'pg'` to your Gemfile 
3. Has anyone written a version compatibility matrix? 
4. Has anyone written a migration guide up the versions?  

I would be willing to contribuite on #3 and #4, just wondering first if anything exists.  

Thanks!

Don

[Don P]

Version compatibility finding #1:  Rails 5.1.5. is required to use pg gem 1.0 or higher.