influxdb query basic percentage calculation - influxdb

Question

I want calculate a division between a number of values different form zero in a specific table and the number of value equal to zero in the same table
SELECT (count("value") WHERE value = 0 / count("value") WHERE value != 0) * 100 FROM "ping_rtt" WHERE time < now() - 15
Obviously this is wrong and I was wondering what could me the correct way to structure the query.

Answer 1

If your field value consists of just zeros or ones; you can easily calculate percentage as:
SELECT 100*sum(value)/count(value) from your_metric
Or simply use Mean function instead of count/sum.
But if value consists of any arbitrary numbers; there is a tricky way (based on this fact that current InfluxDB implementation calculates zero/zero as zero) to achieve this :) You can first map your field value to zeros and ones and then calculate percentage:
SELECT 100*count(map_value)/sum(map_value) FROM (SELECT value/value as map_value FROM your_metric)
It works properly in my influxdb 1.6.0; suppose there is a metric called metric which contain a field val as:
> select * from metric
name: metric
time tag val
---- --- ---
1539780859073434500 15
1539780862064944400 10
1539780865272757400 7
1539780867449546100 0
1539780880145442700 -8
1539781131768616600 12 0
1539781644977103800 12 0.5
1539781649113051900 12 1.5
as you can see, there are different float number as 0,-8,1.5,0.5 and so on.
we can now map our val field to zero or one:
> select val/val as normal_val from metric
name: metric
time normal_val
---- ----------
1539780859073434500 1
1539780862064944400 1
1539780865272757400 1
1539780867449546100 0
1539780880145442700 1
1539781131768616600 0
1539781644977103800 1
1539781649113051900 1