One thing you can do to speed things up is to eliminate the `=~` in your
query. Using regexp matching means it has to do a string search over every
instance in your Prometheus for each metric. Using exact matching (`=`)
will speed things up a lot. Although you won't be able to do multiple
matching if you want that in your dashboard variables.
On Mon, Sep 18, 2023 at 7:58 AM David Leibovic <david.leibo...@gmail.com>
wrote:
> Hi there, I'm trying to optimize a slow query of this form:
>
> (1 * avg_over_time(foo{instance=~"$i"}[$interval]) <= 10) or
> (2 * avg_over_time(foo{instance=~"$i"}[$interval]) <= 20) or
> (3 * avg_over_time(foo{instance=~"$i"}[$interval]) <= 30) or
> (10 * avg_over_time(foo{instance=~"$i"}[$interval]))
>
> I suspect it's slow because of the many duplicate calls to
> avg_over_time(foo{instance=~"$i"}[$interval])
>
> Is there some way to only call the avg_over_time function once and re-use
> the results subsequently? I'm using Prometheus in conjunction with Grafana,
> in case it's relevant.
>
> The full query I'm trying to optimize is much more complicated, but I
> figured the above would be enough to understand the problem. But in case
> it's helpful, here is the full query I am trying to optimize (it's an Air
> Quality Index computation):
>
> ((50 - 0) / (12 - 0) *
> ((avg_over_time(ambient_pm25_env{instance=~"$room.*"}[$aqi_interval]) <=
> 12) - 0) + 0) or
> ((100 - 51) / (35.4 - 12.1) *
> ((avg_over_time(ambient_pm25_env{instance=~"$room.*"}[$aqi_interval]) > 12
> and avg_over_time(ambient_pm25_env{instance=~"$room.*"}[$aqi_interval]) <=
> 35.4) - 12.1) + 51) or
> ((150 - 101) / (55.4 - 35.5) *
> ((avg_over_time(ambient_pm25_env{instance=~"$room.*"}[$aqi_interval]) >
> 35.4 and
> avg_over_time(ambient_pm25_env{instance=~"$room.*"}[$aqi_interval]) <=
> 55.4) - 35.5) + 101) or
> ((200 - 151) / (150.4 - 55.5) *
> ((avg_over_time(ambient_pm25_env{instance=~"$room.*"}[$aqi_interval]) >
> 55.4 and
> avg_over_time(ambient_pm25_env{instance=~"$room.*"}[$aqi_interval]) <=
> 150.4) - 55.5) + 151) or
> ((300 - 201) / (250.4 - 150.5) *
> ((avg_over_time(ambient_pm25_env{instance=~"$room.*"}[$aqi_interval]) >
> 150.4 and
> avg_over_time(ambient_pm25_env{instance=~"$room.*"}[$aqi_interval]) <=
> 250.4) - 150.5) + 201) or
> ((400 - 301) / (350.4 - 250.5) *
> ((avg_over_time(ambient_pm25_env{instance=~"$room.*"}[$aqi_interval]) >
> 250.4 and
> avg_over_time(ambient_pm25_env{instance=~"$room.*"}[$aqi_interval]) <=
> 350.4) - 250.5) + 301) or
> ((500 - 401) / (500.4 - 350.5) *
> ((avg_over_time(ambient_pm25_env{instance=~"$room.*"}[$aqi_interval]) >
> 350.4 and
> avg_over_time(ambient_pm25_env{instance=~"$room.*"}[$aqi_interval]) <=
> 500.4) - 350.5) + 401) or
> clamp_max(avg_over_time(ambient_pm25_env{instance=~"$room.*"}[$aqi_interval]),
> 600)
>
> Thanks for any help you can provide!
>
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