Transformers: Support adding the row index using calculate field transformer (#65148)

docs/sources/panels-visualizations/query-transform-data/transform-data/index.md

@@ -89,6 +89,7 @@ Use this transformation to add a new field calculated from two other fields. Eac
 - **Mode -** Select a mode:
   - **Reduce row -** Apply selected calculation on each row of selected fields independently.
   - **Binary option -** Apply basic math operation(sum, multiply, etc) on values in a single row from two selected fields.
+  - **Index -** Will insert a field with the row index.
 - **Field name -** Select the names of fields you want to use in the calculation for the new field.
 - **Calculation -** If you select **Reduce row** mode, then the **Calculation** field appears. Click in the field to see a list of calculation choices you can use to create the new field. For information about available calculations, refer to [Calculation types]({{< relref "../../calculation-types" >}}).
 - **Operation -** If you select **Binary option** mode, then the **Operation** fields appear. These fields allow you to do basic math operations on values in a single row from two selected fields. You can also use numerical values for binary operations.

packages/grafana-data/src/transformations/transformers/calculateField.test.ts

@@ -222,6 +222,22 @@ describe('calculateField transformer w/ timeseries', () => {
     });
   });
 
+  it('can add index field', async () => {
+    const cfg = {
+      id: DataTransformerID.calculateField,
+      options: {
+        mode: CalculateFieldMode.Index,
+        replaceFields: true,
+      },
+    };
+
+    await expect(transformDataFrame([cfg], [seriesBC])).toEmitValuesWith((received) => {
+      const data = received[0][0];
+      expect(data.fields.length).toEqual(1);
+      expect(data.fields[0].values.toArray()).toEqual([0, 1]);
+    });
+  });
+
   it('uses template variable substituion', async () => {
     const cfg = {
       id: DataTransformerID.calculateField,

packages/grafana-data/src/transformations/transformers/calculateField.ts

@@ -5,7 +5,7 @@ import { getTimeField } from '../../dataframe/processDataFrame';
 import { getFieldDisplayName } from '../../field';
 import { DataFrame, DataTransformerInfo, Field, FieldType, NullValueMode, Vector } from '../../types';
 import { BinaryOperationID, binaryOperators } from '../../utils/binaryOperators';
-import { ArrayVector, BinaryOperationVector, ConstantVector } from '../../vector';
+import { ArrayVector, BinaryOperationVector, ConstantVector, IndexVector } from '../../vector';
 import { AsNumberVector } from '../../vector/AsNumberVector';
 import { RowVector } from '../../vector/RowVector';
 import { doStandardCalcs, fieldReducers, ReducerID } from '../fieldReducer';
@@ -19,6 +19,7 @@ import { noopTransformer } from './noop';
 export enum CalculateFieldMode {
   ReduceRow = 'reduceRow',
   BinaryOperation = 'binary',
+  Index = 'index',
 }
 
 export interface ReduceOptions {
@@ -98,6 +99,22 @@ export const calculateFieldTransformer: DataTransformerInfo<CalculateFieldTransf
           };
 
           creator = getBinaryCreator(defaults(binaryOptions, defaultBinaryOptions), data);
+        } else if (mode === CalculateFieldMode.Index) {
+          return data.map((frame) => {
+            const f = {
+              name: options.alias ?? 'Row',
+              type: FieldType.number,
+              values: new IndexVector(frame.length),
+              config: {
+                min: 0,
+                max: frame.length - 1,
+              },
+            };
+            return {
+              ...frame,
+              fields: options.replaceFields ? [f] : [...frame.fields, f],
+            };
+          });
         }
 
         // Nothing configured
@@ -235,16 +252,21 @@ export function getNameFromOptions(options: CalculateFieldTransformerOptions) {
     return options.alias;
   }
 
-  if (options.mode === CalculateFieldMode.BinaryOperation) {
-    const { binary } = options;
-    return `${binary?.left ?? ''} ${binary?.operator ?? ''} ${binary?.right ?? ''}`;
-  }
-
-  if (options.mode === CalculateFieldMode.ReduceRow) {
-    const r = fieldReducers.getIfExists(options.reduce?.reducer);
-    if (r) {
-      return r.name;
+  switch (options.mode) {
+    case CalculateFieldMode.BinaryOperation: {
+      const { binary } = options;
+      return `${binary?.left ?? ''} ${binary?.operator ?? ''} ${binary?.right ?? ''}`;
     }
+    case CalculateFieldMode.ReduceRow:
+      {
+        const r = fieldReducers.getIfExists(options.reduce?.reducer);
+        if (r) {
+          return r.name;
+        }
+      }
+      break;
+    case CalculateFieldMode.Index:
+      return 'Row';
   }
 
   return 'math';

public/app/features/transformers/editors/CalculateFieldTransformerEditor.tsx

@@ -37,6 +37,7 @@ interface CalculateFieldTransformerEditorState {
 const calculationModes = [
   { value: CalculateFieldMode.BinaryOperation, label: 'Binary operation' },
   { value: CalculateFieldMode.ReduceRow, label: 'Reduce row' },
+  { value: CalculateFieldMode.Index, label: 'Row index' },
 ];
 
 const okTypes = new Set<FieldType>([FieldType.time, FieldType.number, FieldType.string]);