def group_clause
time_zone = @time_zone.tzinfo.name
day_start_column = "#{column}::timestamptz AT TIME ZONE ? - INTERVAL ?"
day_start_interval = "#{day_start} second"
query =
case period
when :minute_of_hour
["EXTRACT(MINUTE FROM #{day_start_column})::integer", time_zone, day_start_interval]
when :hour_of_day
["EXTRACT(HOUR FROM #{day_start_column})::integer", time_zone, day_start_interval]
when :day_of_week
["EXTRACT(DOW FROM #{day_start_column})::integer", time_zone, day_start_interval]
when :day_of_month
["EXTRACT(DAY FROM #{day_start_column})::integer", time_zone, day_start_interval]
when :day_of_year
["EXTRACT(DOY FROM #{day_start_column})::integer", time_zone, day_start_interval]
when :month_of_year
["EXTRACT(MONTH FROM #{day_start_column})::integer", time_zone, day_start_interval]
when :week
["(DATE_TRUNC('day', #{day_start_column} - INTERVAL '1 day' * ((? + EXTRACT(DOW FROM #{day_start_column})::integer) % 7)) + INTERVAL ?)::date", time_zone, day_start_interval, 13 - week_start, time_zone, day_start_interval, day_start_interval]
when :custom
if @adapter_name == "Redshift"
["TIMESTAMP 'epoch' + (FLOOR(EXTRACT(EPOCH FROM #{column}::timestamp) / ?) * ?) * INTERVAL '1 second'", n_seconds, n_seconds]
else
["TO_TIMESTAMP(FLOOR(EXTRACT(EPOCH FROM #{column}::timestamptz) / ?) * ?)", n_seconds, n_seconds]
end
when :day, :month, :quarter, :year
["DATE_TRUNC(?, #{day_start_column})::date", period, time_zone, day_start_interval]
else
["DATE_TRUNC(?, #{day_start_column}) AT TIME ZONE ?", period, time_zone, day_start_interval, time_zone]
end
clean_group_clause(@relation.send(:sanitize_sql_array, query))
end