filter() function

The filter() function filters data based on conditions defined in a predicate function (fn). The output tables have the same schema as the corresponding input tables.

Function type: Transformation
Output data type: Object

filter(fn: (r) => r._measurement == "cpu")



A single argument predicate function that evaluates true or false. Records are passed to the function. Those that evaluate to true are included in the output tables. Records that evaluate to null or false are not included in the output tables.

Data type: Function

Objects evaluated in fn functions are represented by r, short for “record” or “row”.

Make sure fn parameter names match each specified parameter. To learn why, see Match parameter names.


  |> range(start:-1h)
  |> filter(fn: (r) =>
    r._measurement == "cpu" and
    r._field == "usage_system" and
    r.cpu == "cpu-total"


This documentation is open source. See a typo? Please, open an issue.

Need help getting up and running? Get Support