PostgreSQL Advent Calendar 2014に参加しています。 数日前、SimonがPgSQL-Hackersに面白いパッチを投げてきた。 曰く、 KaiGai, David Rowley and myself have all made mention of various ways we could optimize aggregates. Following WIP patch adds an extra function called a "combining function", that is intended to allow the user to specify a semantically correct way of breaking down an aggregate into multiple steps. Gents, is this what