Guess grouping by month is not yet supported. When will it be added? Is the following an appropriate workaround in the mean time?
- Add a month tag (possible values will be either 1 to 12, 0 to 11, jan to dec, etc) and year tag.
- Calculate the month and year based on the timestamp using some other means.
- Insert record with timestamp, month, year.
- Query the data using GROUP BY year, month.