VirtualField

Source: src/Axiom/VirtualField.ts

An Axiom virtual field — a saved APL expression that appears as a derived column on a dataset at query time. Use these to standardise common computations (status classes, latency buckets, parsed JSON paths) so dashboards and monitors don’t have to redefine them.

Bound to a single dataset; changing the dataset triggers a replacement.

Creating a Virtual Field

HTTP status class (e.g. 200 → “2xx”)

yield* Axiom.VirtualField("status-class", {
  dataset: "my-app-traces",
  name: "status_class",
  description: "HTTP response class bucket",
  expression: 'strcat(tostring(toint(status / 100)), "xx")',
  type: "string",
});

Latency bucket in seconds

yield* Axiom.VirtualField("latency-bucket", {
  dataset: "my-app-traces",
  name: "latency_bucket_s",
  expression: "bin(duration_ms / 1000.0, 0.5)",
  type: "number",
  unit: "s",
});