This document summarizes the differences between the ruby-postgres and postgres-pr PostgreSQL database adapters for ActiveRecord in Ruby. It notes that postgres-pr is pure Ruby while ruby-postgres uses the libpq C library. It provides examples showing that postgres-pr is missing some functionality that ruby-postgres has like ParameterStatus support and asynchronous query execution. It concludes that while postgres-pr is useful, it has limitations that may prevent ActiveRecord from working properly, so ruby-postgres is likely better supported.