Check if a value exists

Use the Flux exists operator to check if a record contains a key or if that key’s value is null.

p = {firstName: "John", lastName: "Doe", age: 42}

exists p.firstName
// Returns true

exists p.height
// Returns false

If you’re just getting started with Flux queries, check out the following:

Use exists with row functions ( filter(), map(), reduce()) to check if a row includes a column or if the value for that column is null.

Filter null values

from(bucket: "example-bucket")
  |> range(start: -5m)
  |> filter(fn: (r) => exists r._value)

Map values based on existence

from(bucket: "default")
  |> range(start: -30s)
  |> map(fn: (r) => ({
      r with
        if exists r._value then "${r._field} is ${string(v:r._value)}."
        else "${r._field} has no value."

Ignore null values in a custom aggregate function

customSumProduct = (tables=<-) =>
    |> reduce(
      identity: {sum: 0.0, product: 1.0},
      fn: (r, accumulator) => ({
        r with
          if exists r._value then r._value + accumulator.sum
          else accumulator.sum,
          if exists r._value then r.value * accumulator.product
          else accumulator.product

New! Cloud or OSS?

InfluxDB OSS 2.0 now generally available!

InfluxDB OSS 2.0 is now generally available and ready for production use. See the InfluxDB OSS 2.0 release notes.

For information about upgrading to InfluxDB OSS 2.0, see: