问Ruby ActiveRecord组和平均“语法错误在或接近”AS“

EN

params = {device_id: "u100", device_point: "1", point_no: "1", max_date: "2016-12-01 12:00", min_date: "2016-12-01 11:40"}

.group("date_trunc('minute', device_time)").average('point_data_val')

device_data = DeviceDatum.select('device_time, point_data_val').filter(params.slice(:device_id, :device_point, :point_no, :iot_version, :iot_time, :device_time, :point_data_type, :point_data_val, :point_bat_val,:min_val, :max_val, :min_date, :max_date)).limit(1008).group("date_trunc('minute', device_time)").average('point_data_val')
   (240.3ms)  SELECT  AVG("device_data"."point_data_val") AS average_point_data_val, date_trunc('minute', device_time) AS date_trunc_minute_device_time FROM "device_data" WHERE "device_data"."device_id" = $1 AND "device_data"."device_point" = $2 AND "device_data"."point_no" = $3 AND (device_time >= '2016-12-01 11:40') AND (device_time <= '2016-12-01 12:00') GROUP BY date_trunc('minute', device_time) LIMIT 1008  [["device_id", "u100"], ["device_point", 1], ["point_no", 1]]
=> {2016-12-01 11:41:00 +0900=>#<BigDecimal:7f91599cfbc0,'-0.4816E1',18(27)>, 2016-12-01 11:51:00 +0900=>#<BigDecimal:7f91599cf8f0,'-0.4868E1',18(27)>}

DeviceDatum.select('device_time, point_data_val')
.filter(params.slice(:device_id, :device_point, :point_no, :iot_version, :iot_time, :device_time, 
:point_data_type, :point_data_val, :point_bat_val,:min_val, :max_val, :min_date, 
:max_date)).limit(1008)
.group("date_trunc('hour', device_time) AS hour_stump,
(extract(minute FROM device_time)::int / 10) 
AS min10_slot,count(*)").average('point_data_val')

ActiveRecord::StatementInvalid: PG::SyntaxError: ERROR:  syntax error at or near "AS"
LINE 1: ... 12:00') GROUP BY date_trunc('hour', device_time) AS hour_st... : SELECT  AVG("device_data"."point_data_val") AS average_point_data_val, date_trunc('hour', device_time) AS hour_stump,(extract(minute FROM device_time)::int / 10) AS min10_slot,count(*) AS date_trunc_hour_device_time_as_hour_stump_extract_minute_from_d FROM "device_data" WHERE "device_data"."device_id" = $1 AND "device_data"."device_point" = $2 AND "device_data"."point_no" = $3 AND (device_time >= '2016-12-01 11:40') AND (device_time <= '2016-12-01 12:00') GROUP BY date_trunc('hour', device_time) AS hour_stump,(extract(minute FROM device_time)::int / 10) AS min10_slot,count(*) LIMIT 1008
from ...../bundle/ruby/2.1.0/gems/activerecord-4.2.6/lib/active_record/connection_adapters/postgresql_adapter.rb:637:in `prepare'

 SELECT
   AVG("device_data"."point_data_val") AS average_point_data_val,
   date_trunc('hour', device_time) AS hour_stump,
   (
      extract(minute 
   FROM
      device_time)::int / 10
   )
   AS min10_slot,
   count(*) AS date_trunc_hour_device_time_as_hour_stump_extract_minute_from_d 
FROM
   "device_data" 
WHERE
   "device_data"."device_id" = $1 
   AND "device_data"."device_point" = $2 
   AND "device_data"."point_no" = $3 
   AND 
   (
      device_time >= '2016-12-01 11:40'
   )
   AND 
   (
      device_time <= '2016-12-01 12:00'
   )
GROUP BY
   date_trunc('hour', device_time) AS hour_stump,
   (
      extract(minute 
   FROM
      device_time)::int / 10
   )
   AS min10_slot,
   count(*) LIMIT 1008