Explore: reuse table merge from table panel

- Extracted table panel's merge logic to combine multiple tables into one
- Put the merge logic into the table model as it merges multiple table
  models
- make use of merge in Explore's table query response handler
- copied tests over to table model spec, kept essential tests in
  transformer spec

public/app/core/specs/table_model.test.ts

@@ -1,4 +1,4 @@
-import TableModel from 'app/core/table_model';
+import TableModel, { mergeTablesIntoModel } from 'app/core/table_model';
 
 describe('when sorting table desc', () => {
   let table;
@@ -79,3 +79,118 @@ describe('when sorting with nulls', () => {
     expect(values).toEqual([null, null, 'd', 'c', 'b', 'a', '', '']);
   });
 });
+
+describe('mergeTables', () => {
+  const time = new Date().getTime();
+
+  const singleTable = new TableModel({
+    type: 'table',
+    columns: [{ text: 'Time' }, { text: 'Label Key 1' }, { text: 'Value' }],
+    rows: [[time, 'Label Value 1', 42]],
+  });
+
+  const multipleTablesSameColumns = [
+    new TableModel({
+      type: 'table',
+      columns: [{ text: 'Time' }, { text: 'Label Key 1' }, { text: 'Label Key 2' }, { text: 'Value #A' }],
+      rows: [[time, 'Label Value 1', 'Label Value 2', 42]],
+    }),
+    new TableModel({
+      type: 'table',
+      columns: [{ text: 'Time' }, { text: 'Label Key 1' }, { text: 'Label Key 2' }, { text: 'Value #B' }],
+      rows: [[time, 'Label Value 1', 'Label Value 2', 13]],
+    }),
+    new TableModel({
+      type: 'table',
+      columns: [{ text: 'Time' }, { text: 'Label Key 1' }, { text: 'Label Key 2' }, { text: 'Value #C' }],
+      rows: [[time, 'Label Value 1', 'Label Value 2', 4]],
+    }),
+    new TableModel({
+      type: 'table',
+      columns: [{ text: 'Time' }, { text: 'Label Key 1' }, { text: 'Label Key 2' }, { text: 'Value #C' }],
+      rows: [[time, 'Label Value 1', 'Label Value 2', 7]],
+    }),
+  ];
+
+  const multipleTablesDifferentColumns = [
+    new TableModel({
+      type: 'table',
+      columns: [{ text: 'Time' }, { text: 'Label Key 1' }, { text: 'Value #A' }],
+      rows: [[time, 'Label Value 1', 42]],
+    }),
+    new TableModel({
+      type: 'table',
+      columns: [{ text: 'Time' }, { text: 'Label Key 2' }, { text: 'Value #B' }],
+      rows: [[time, 'Label Value 2', 13]],
+    }),
+    new TableModel({
+      type: 'table',
+      columns: [{ text: 'Time' }, { text: 'Label Key 1' }, { text: 'Value #C' }],
+      rows: [[time, 'Label Value 3', 7]],
+    }),
+  ];
+
+  it('should return the single table as is', () => {
+    const table = mergeTablesIntoModel(new TableModel(), singleTable);
+    expect(table.columns.length).toBe(3);
+    expect(table.columns[0].text).toBe('Time');
+    expect(table.columns[1].text).toBe('Label Key 1');
+    expect(table.columns[2].text).toBe('Value');
+  });
+
+  it('should return the union of columns for multiple tables', () => {
+    const table = mergeTablesIntoModel(new TableModel(), ...multipleTablesSameColumns);
+    expect(table.columns.length).toBe(6);
+    expect(table.columns[0].text).toBe('Time');
+    expect(table.columns[1].text).toBe('Label Key 1');
+    expect(table.columns[2].text).toBe('Label Key 2');
+    expect(table.columns[3].text).toBe('Value #A');
+    expect(table.columns[4].text).toBe('Value #B');
+    expect(table.columns[5].text).toBe('Value #C');
+  });
+
+  it('should return 1 row for a single table', () => {
+    const table = mergeTablesIntoModel(new TableModel(), singleTable);
+    expect(table.rows.length).toBe(1);
+    expect(table.rows[0][0]).toBe(time);
+    expect(table.rows[0][1]).toBe('Label Value 1');
+    expect(table.rows[0][2]).toBe(42);
+  });
+
+  it('should return 2 rows for a multiple tables with same column values plus one extra row', () => {
+    const table = mergeTablesIntoModel(new TableModel(), ...multipleTablesSameColumns);
+    expect(table.rows.length).toBe(2);
+    expect(table.rows[0][0]).toBe(time);
+    expect(table.rows[0][1]).toBe('Label Value 1');
+    expect(table.rows[0][2]).toBe('Label Value 2');
+    expect(table.rows[0][3]).toBe(42);
+    expect(table.rows[0][4]).toBe(13);
+    expect(table.rows[0][5]).toBe(4);
+    expect(table.rows[1][0]).toBe(time);
+    expect(table.rows[1][1]).toBe('Label Value 1');
+    expect(table.rows[1][2]).toBe('Label Value 2');
+    expect(table.rows[1][3]).toBeUndefined();
+    expect(table.rows[1][4]).toBeUndefined();
+    expect(table.rows[1][5]).toBe(7);
+  });
+
+  it('should return 2 rows for multiple tables with different column values', () => {
+    const table = mergeTablesIntoModel(new TableModel(), ...multipleTablesDifferentColumns);
+    expect(table.rows.length).toBe(2);
+    expect(table.columns.length).toBe(6);
+
+    expect(table.rows[0][0]).toBe(time);
+    expect(table.rows[0][1]).toBe('Label Value 1');
+    expect(table.rows[0][2]).toBe(42);
+    expect(table.rows[0][3]).toBe('Label Value 2');
+    expect(table.rows[0][4]).toBe(13);
+    expect(table.rows[0][5]).toBeUndefined();
+
+    expect(table.rows[1][0]).toBe(time);
+    expect(table.rows[1][1]).toBe('Label Value 3');
+    expect(table.rows[1][2]).toBeUndefined();
+    expect(table.rows[1][3]).toBeUndefined();
+    expect(table.rows[1][4]).toBeUndefined();
+    expect(table.rows[1][5]).toBe(7);
+  });
+});