Documentation

Check if a value exists

This page documents an earlier version of InfluxDB. InfluxDB v2.2 is the latest stable version. View this page in the v2.2 documentation.

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

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