CODEWITHSUNDEEP
influxdb
Christophe Blin
Christophe Blin

Reputation: 1909

Counting boolean values in flux query

I have a bucket where one field is a boolean

I'd like to count the number of true and the number of false for each hour

from(bucket: "xxx")
  |> range(start: v.timeRangeStart, stop: v.timeRangeStop)
  |> window(every: 1h)
  |> filter(fn: (r) => r["_measurement"] == "xxx")
  |> filter(fn: (r) => r["_field"] == "myBoolField")
  |> group(columns: ["_stop"])

Because this is issued from a cron that runs every minute (more or less), this will give something like :

table _start              _stop            _time            _value otherfield1 otherfield2
0     2021-05-18T19:00:00 2021-05-18T20:00 2021-05-18T19:01 false  xxx         xxx
0     2021-05-18T19:00:00 2021-05-18T20:00 2021-05-18T19:02 true   xxx         xxx
0     2021-05-18T19:00:00 2021-05-18T20:00 2021-05-18T19:03 true   xxx         xxx
...
1     2021-05-18T20:00:00 2021-05-18T21:00 2021-05-18T20:01 false  xxx         xxx
1     2021-05-18T20:00:00 2021-05-18T21:00 2021-05-18T20:02 false  xxx         xxx
1     2021-05-18T20:00:00 2021-05-18T21:00 2021-05-18T20:03 false  xxx         xxx
...

Now, I'd like to count the total, the number of false and the number of true for each hour (so for each table) but without losing/dropping the other fields

So I'd like a structure like

table _stop            _value nbFalse nbTrue otherfield1 otherfield2
0     2021-05-18T20:00 59     1       58     xxx         xxx
1     2021-05-18T21:00 55     4       51     xxx         xxx

I've tried many combinations of pivot, count, ... without success

From my understanding, the correct way to do is

  1. drop _start and _time

  2. duplicate _value into nbTrue and nbFalse

  3. re-aggregate by _stop to keep only true in nbTrue and false in nbFalse

  4. count the three columns _value, nbTrue and nbFalse

    |> drop(columns: ["_start", "_time"]) |> duplicate(column: "_value", as: "nbTrue") |> duplicate(column: "_value", as: "nbFalse")

but I am stucked at step 3...

Upvotes: 2

Views: 1902

Answers (2)

Christophe Blin
Christophe Blin

Reputation: 1909

Answer from @dskalec should work, I did not test it directly because, in the end, I needed to aggregate more than just the boolean field

here is my query, you can see that it is using the same aggregate+reduce (I just use a pivot before to have more than one field to aggregate)

from(bucket: "rt")
  |> range(start: v.timeRangeStart, stop: v.timeRangeStop)
  |> filter(fn: (r) => r["_measurement"] == "xxx")

  |> pivot(
    rowKey:["_time"],
    columnKey: ["_field"],
    valueColumn: "_value"
  )

  |> window(every: 1h, createEmpty: true)

  |> reduce(fn: (r, accumulator) => ({ 
      nb: accumulator.nb + 1,
      field1: accumulator.field1 + r["field1"], //field1 is an int
      field2: if r["field2"] then accumulator.field2 + 1 else accumulator.field2, //field2 is a boolean
    }),
    identity: {nb: 0, field1: 0, field2: 0}
  )

  |> duplicate(column: "_stop", as: "_time")
  |> drop(columns: ["_start", "_stop"])

Upvotes: 1

dskalec
dskalec

Reputation: 326

Didn't test it, but I have something similar to this on my mind:

from(bucket: "xxx")
  |> range(start: v.timeRangeStart, stop: v.timeRangeStop)
  |> filter(fn: (r) => r["_measurement"] == "xxx")
  |> filter(fn: (r) => r["_field"] == "myBoolField")
  |> aggregateWindow(
        every: 1h,
        fn: (column, tables=<-) => tables |> reduce(
            identity: {true_count: 0.0},
            fn: (r, accumulator) => ({
                true_count:
                    if r._value == true then accumulator.true_count + 1.0
                    else accumulator.true_count + 0.0
            })
        )
    )

I got this from the docs and adjusted it a bit, I think it should get you what you need.

Upvotes: 2

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