support duplicate field names in arrow format (#22705)

packages/grafana-data/src/dataframe/ArrowDataFrame.test.ts

@@ -71,7 +71,27 @@ describe('Read/Write arrow Table to DataFrame', () => {
     expect(after).toEqual(before);
   });
 
-  test('should parse output with dataframe', () => {
+  test('should support duplicate field names', () => {
+    const frame = toDataFrame({
+      name: 'Hello',
+      refId: 'XYZ',
+      fields: [
+        { name: 'time', config: {}, type: FieldType.time, values: [1, 2, 3] },
+        { name: 'a', values: [1, 2, 3] },
+        { name: 'a', values: ['a', 'b', 'c'] },
+      ],
+    });
+
+    const table = grafanaDataFrameToArrowTable(frame);
+    expect(table.length).toEqual(frame.length);
+
+    // Now back to DataFrame
+    const before = JSON.stringify(toDataFrameDTO(frame), null, 2);
+    const after = JSON.stringify(toDataFrameDTO(arrowTableToDataFrame(table)), null, 2);
+    expect(after).toEqual(before);
+  });
+
+  test('should read all types', () => {
     const fullpath = path.resolve(__dirname, './__snapshots__/all_types.golden.arrow');
     const arrow = fs.readFileSync(fullpath);
     const table = Table.from([arrow]);

packages/grafana-data/src/dataframe/ArrowDataFrame.ts

@@ -72,7 +72,7 @@ export function arrowTableToDataFrame(table: Table): ArrowDataFrame {
       }
 
       fields.push({
-        name: col.name,
+        name: stripFieldNamePrefix(col.name),
         type,
         values,
         config: parseOptionalMeta(col.metadata.get('config')) || {},
@@ -91,6 +91,17 @@ export function arrowTableToDataFrame(table: Table): ArrowDataFrame {
   };
 }
 
+// fieldNamePrefixSep is the delimiter used with fieldNamePrefix.
+const fieldNamePrefixSep = '🦥: ';
+
+function stripFieldNamePrefix(name: string): string {
+  const idx = name.indexOf(fieldNamePrefixSep);
+  if (idx > 0) {
+    return name.substring(idx + fieldNamePrefixSep.length);
+  }
+  return name;
+}
+
 function toArrowVector(field: Field): ArrowVector {
   // OR: Float64Vector.from([1, 2, 3]));
 
@@ -117,10 +128,17 @@ export function grafanaDataFrameToArrowTable(data: DataFrame): Table {
   if (table instanceof Table) {
     return table as Table;
   }
+  // Make sure the names are unique
+  const names = new Set<string>();
 
   table = Table.new(
-    data.fields.map(field => {
-      const column = Column.new(field.name, toArrowVector(field));
+    data.fields.map((field, index) => {
+      let name = field.name;
+      if (names.has(field.name)) {
+        name = `${index}${fieldNamePrefixSep}${field.name}`;
+      }
+      names.add(name);
+      const column = Column.new(name, toArrowVector(field));
       if (field.labels) {
         column.metadata.set('labels', JSON.stringify(field.labels));
       }

packages/grafana-data/src/dataframe/__snapshots__/ArrowDataFrame.test.ts.snap

@@ -103,7 +103,7 @@ Array [
 ]
 `;
 
-exports[`Read/Write arrow Table to DataFrame should parse output with dataframe 1`] = `
+exports[`Read/Write arrow Table to DataFrame should read all types 1`] = `
 Object {
   "fields": Array [
     Object {