Issue with Flux Query Handling Empty Results

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1

Hello,

I’m encountering an issue with a Flux query, and I’d appreciate some guidance on how to handle it properly. Here’s the problematic query:

flux

import "http/requests"
import "experimental/json"
import "array"
import "join"
import "strings"
import "math"

mainQuery = from(bucket: "foobar")
  |> range(start: -7d)
  |> filter(fn: (r) => r["_measurement"] == "muh")
  |> filter(fn: (r) => r["_field"] == "baz")
  |> last()
  |> pivot(rowKey: ["lala"], columnKey: ["_field"], valueColumn: "_value")
  |> group()
  |> filter(fn: (r) =>
    r.baz >= 42
    and r.baz <= 100
  )
  |> sort(columns: ["baz"], desc: true)
  |> limit(n: 40)
  |> keep(columns: ["baz", "dingdong",])

requestParams = mainQuery
  |> unique(column: "dingdong")
  |> findColumn(fn: (key) => true, column: "dingdong")

response = requests.get(url: "http://<MAGIC-HOST>/id2name", params: ["id[]": requestParams])
data = json.parse(data: response.body)
id2Name = array.from(rows: data)

translated = join.left(
  left: mainQuery,
  right: id2Name,
  on: (l, r) => l.dingdong == r.id,
  as: (l, r) => ({l with rName: (if exists r.name then r.name else l.dingdong)}),
)
  |> sort(columns: ["baz"], desc: true)

yield translated

The issue arises when mainQuery returns an empty result. In this case, the subsequent line id2Name = array.from(rows: data) throws an error because data is empty. I want the entire query to return an empty result when mainQuery has no results, to avoid this error.

Could you please provide guidance on how to handle this situation gracefully? I want the query to terminate immediately and return an empty result when no data is available in mainQuery.

Thank you for your help!

Best regards, Volker.

2

okay, this is my current approach:

import "http/requests"
import "experimental/json"
import "array"
import "join"
import "strings"
import "math"

mainQuery = from(bucket: "foobar")
  |> range(start: -7d)
  |> filter(fn: (r) => r["_measurement"] == "muh")
  |> filter(fn: (r) => r["_field"] == "baz")
  |> last()
  |> pivot(rowKey: ["lala"], columnKey: ["_field"], valueColumn: "_value")
  |> group()
  |> filter(fn: (r) =>
    r.baz >= 42
    and r.baz <= 100
  )
  |> sort(columns: ["baz"], desc: true)
  |> limit(n: 40)
  |> keep(columns: ["baz", "dingdong",])
  
check = exists (mainQuery |> count(column: "dingdong")  |> findRecord( fn: (key) => true, idx: 0) ).dingdong

resultFunc = (mainQuery) => {
  requestParams = mainQuery
    |> unique(column: "dingdong")
    |> findColumn(fn: (key) => true, column: "dingdong")

  response = requests.get(url: "http://<MAGIC-HOST>/id2name", params: ["id[]": requestParams])
  data = json.parse(data: response.body)
  id2Name = array.from(rows: data)

  translated = join.left(
    left: mainQuery,
    right: id2Name,
    on: (l, r) => l.dingdong == r.id,
    as: (l, r) => ({l with rName: (if exists r.name then r.name else l.dingdong)}),
  )
    |> sort(columns: ["baz"], desc: true)
}

if check then
    resultFunc(mainQuery: mainQuery) |> yield()
else
    mainQuery |> yield()

any additional suggestions?

regards, volker.

3

Hello @skydiablo,
Thank you for sharing your approach with the community! We really appreciate it