On 7th of February 2018, Tom Lane committed patch: Support all SQL:2011 options for window frame clauses. This patch adds the ability to use "RANGE offset PRECEDING/FOLLOWING" frame boundaries in window functions. We'd punted on that back in the original patch to add ...

On 12th of February Tom Lane committed patch by Hitoshi Harada: Log Message: ----------- Extend the set of frame options supported for window functions.   This patch allows the frame to start from CURRENT ROW (in either RANGE or ROWS mode), and it also adds support ...