Problem using Pivot Table where externalProcessing=true and custom backend

I’m having trouble getting example from working with external processing. I have modified the code this way:

webix.ready(function() {

  class MyBackend extends {
    data() {
      return webix.promise.resolve(pivotData);

    view: "pivot",
    structure: {
      rows: ["form", "name"],
      columns: ["year"],
      values: [{ name: "oil", operation: ["min", "sum"] }],
    externalProcessing: true,
    override: new Map([[, MyBackend]]),

As you can see, the only change is to include externalProcessing: true. When set to true, the code fails with error “Incorrect formula in values”. When set to false, the example works perfectly. Is there some additional documentation that explains the protocol for external processing?

Hello @markaddleman .

We have updated our documentation about Pivot with externalProcessing enabled.
Please, check the new example with externalProcessing: true and local data as well: Code Snippet .