Join measurements to fieldkeys in InfluxDB using map and reduce functions - influxdb

Question

In InfluxDB 2.x, I need to create a simplified data dictionary listing all of the measurements and their fields. I want to get all of the fieldKeys for all of the measurements within a bucket. The query should get all of the measurements for the bucket, then for each measurement get all of the fieldKeys and concat them into a large string separated with commas. The end result should have two columns with the measurement and list of fieldKeys like the following:
mem,"field1,field2,field3"
cpu,"field1,field2,field3,field4"
I can create the concatenated list of fieldKeys with the following function:
import "influxdata/influxdb/schema"
import "strings"
import "array"
getFieldsForMeasure = (measureName) => schema.measurementFieldKeys(bucket: "mybucket", measurement: measureName)
|> reduce(
fn: (r, accumulator) => ({sum: r._value + "," + accumulator.sum}),
identity: {sum: ""},
)
getFieldsForMeasure(measureName: "mem")
Putting that with a map function and a query for the measruements look like the following:
import "influxdata/influxdb/schema"
import "strings"
import "array"
getFieldsForMeasure = (measureName) => schema.measurementFieldKeys(bucket: "mybucket", measurement: measureName)
|> reduce(
fn: (r, accumulator) => ({sum: r._value + "," + accumulator.sum}),
identity: {sum: ""},
)
data = schema.measurements(bucket: "mybucket")
|> yield()
|> findColumn(
fn: (key) => key._field == "",
column: "_value",
)
data |> map(fn: (r) => ({fieldsList: string(v: getFieldsForMeasure(measureName: r._value))}))
Although, I get this error:
Error: failed to execute query: 400 Bad Request: error #20:1-20:5: expected stream[{A with _value: B}] but found [{A with _value: B}] (array) (argument tables)

Answer 1

It is because findColumn returns an array, but pipeline functions require stream input. It seems that you have just misplaced it in the code, I guess you meant to use it for fields list extraction in getFieldsForMeasure.
So I hope the following returns expected result:
import "influxdata/influxdb/schema"
import "strings"
import "array"
getFieldsForMeasure = (measureName) => schema.measurementFieldKeys(bucket: "mybucket", measurement: measureName)
|> reduce(
fn: (r, accumulator) => ({sum: r._value + "," + accumulator.sum}),
identity: {sum: ""},
)
|> findColumn(column: "sum", fn: (key) => true)
data = schema.measurements(bucket: "mybucket")
data
|> map(fn: (r) => ({r with fieldsList: string(v: getFieldsForMeasure(measureName: r._value)[0])}))
Output:
win_cpu Percent_User_Time,Percent_Processor_Time,Percent_Privileged_Time,Percent_Interrupt_Time,Percent_Idle_Time,Percent_DPC_Time,
win_disk Percent_Idle_Time,Percent_Free_Space,Percent_Disk_Write_Time,Percent_Disk_Time,Percent_Disk_Read_Time,Free_Megabytes,Current_Disk_Queue_Length,
win_mem ...