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:
- Get started with Flux for a conceptual overview of Flux and parts of a Flux query.
- Execute queries to discover a variety of ways to run your queries.
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,
}),
)
Support and feedback
Thank you for being part of our community! We welcome and encourage your feedback and bug reports for InfluxDB and this documentation. To find support, the following resources are available:
InfluxDB Cloud and InfluxDB Enterprise customers can contact InfluxData Support.