Neat library. Just to note that this approach to fake upsert is not safe to concurrent sessions. There were exactly two concurrency-safe ways to implement upsert prior to 9.5:<p>1. An exclusive lock on the table, which is slow as hell
2. A PGPSQL function that attempts to INSERT, catches the duplicate key exception and instead UPDATEs (also handling the case that the row vanishes), which is slower than hell<p>This is why ON CONFLICT is such a huge deal. If it were as simple as checking keys with a SELECT then sending some to INSERT and some to UPDATE it would just be nice syntax sugar.