我在用timescaledb
这基本上只是一个扩展postgres
。它带有一个名为的 SQL 函数time_bucket https://docs.timescale.com/latest/api/api-timescaledb#time_bucket-a-id-time_bucket-a-。我想将此函数与 ORM 结合使用来生成查询,如下所示:
SELECT
time_bucket('1 minute', time) AS tb,
AVG(s0)
FROM measurements
WHERE
time >= to_timestamp(1) AND
time <= to_timestamp(2)
GROUP BY tb
ORDER BY tb ASC;
models.py
:
class Measurement(models.Model):
device_id = models.IntegerField(primary_key=True)
time = models.DateTimeField()
s0 = models.FloatField(blank=True, null=True)
s1 = models.FloatField(blank=True, null=True)
到目前为止我的尝试:
class TimeBucket(Func):
function = 'time_bucket'
template = '%(function)s(\'{bucket_width}\', %(expressions)s)'.format(bucket_width='1 minute')
(Measurement.objects
.values('time')
.annotate(tb=TimeBucket('time'))
.annotate(s_desc=Avg('s0'))
.filter(
time__gte=datetime.fromtimestamp(start),
time__lte=datetime.fromtimestamp(end))
.order_by('tb')
)
结果是:
SELECT
"measurements"."time",
time_bucket('1 minute', "measurements"."time") AS "tb",
(AVG("measurements"."s0")) AS "s_desc"
FROM "measurements"
WHERE (
"measurements"."time" <= 2447-10-02 14:17:01+00:00 AND
"measurements"."time" >= 1970-01-01 00:00:01+00:00
)
GROUP BY "measurements"."time", time_bucket('1 minute', "measurements"."time")
ORDER BY "tb" ASC
正如你所看到的,还剩下两个难看的地方:
- 我如何使用别名
tb
in the GROUP BY
而不是重复它?
- 我只需要查询
time_bucket
and s0
。如何摆脱time
不破坏查询?