TablePanel: Add support for Count calculation per column or per entire dataset

docs/sources/panels-visualizations/visualizations/table/index.md

@@ -160,3 +160,15 @@ Columns with filters applied have a blue funnel displayed next to the title.
 {{< figure src="/static/img/docs/tables/filtered-column.png" max-width="500px" caption="Filtered column" class="docs-image--no-shadow" >}}
 
 To remove the filter, click the blue funnel icon and then click **Clear filter**.
+
+## Table footer
+
+You can use the table footer to show [calculations]({{< relref "../../calculation-types/" >}}) on fields.
+
+After enabling the table footer, you can select your **Calculation** and select the **Fields** that should be calculated. Not selecting any field apply the calculation to all numeric fields.
+
+### Count rows
+
+On selecting the **Count** calculation, you will see the **Count rows** switch.
+
+By enabling this option the footer will show the number of rows in the dataset instead of the number of values in the selected fields.

packages/grafana-data/src/transformations/fieldReducer.ts

@@ -291,7 +291,7 @@ export function doStandardCalcs(field: Field, ignoreNulls: boolean, nullAsZero:
   } as FieldCalcs;
 
   const data = field.values;
-  calcs.count = data.length;
+  calcs.count = ignoreNulls ? data.length : data.toArray().filter((val) => val != null).length;
 
   const isNumberField = field.type === FieldType.number || FieldType.time;
 

packages/grafana-ui/src/components/Table/FooterRow.tsx

@@ -40,9 +40,7 @@ export const FooterRow = (props: FooterRowProps) => {
             data-testid={e2eSelectorsTable.footer}
             style={height ? { height: `${height}px` } : undefined}
           >
-            {footerGroup.headers.map((column: ColumnInstance, index: number) =>
-              renderFooterCell(column, tableStyles, height)
-            )}
+            {footerGroup.headers.map((column: ColumnInstance) => renderFooterCell(column, tableStyles, height))}
           </div>
         );
       })}
@@ -71,10 +69,19 @@ function renderFooterCell(column: ColumnInstance, tableStyles: TableStyles, heig
   );
 }
 
-export function getFooterValue(index: number, footerValues?: FooterItem[]) {
+export function getFooterValue(index: number, footerValues?: FooterItem[], isCountRowsSet?: boolean) {
   if (footerValues === undefined) {
     return EmptyCell;
   }
 
+  if (isCountRowsSet) {
+    const count = footerValues[index];
+    if (typeof count !== 'string') {
+      return EmptyCell;
+    }
+
+    return FooterCell({ value: [{ Count: count }] });
+  }
+
   return FooterCell({ value: footerValues[index] });
 }

packages/grafana-ui/src/components/Table/Table.test.tsx

@@ -399,6 +399,121 @@ describe('Table', () => {
     });
   });
 
+  describe('on table footer enabled and count calculation selected', () => {
+    it('should show count of non-null values', async () => {
+      getTestContext({
+        footerOptions: { show: true, reducer: ['count'] },
+        data: toDataFrame({
+          name: 'A',
+          fields: [
+            {
+              name: 'number',
+              type: FieldType.number,
+              values: [1, 1, 1, 2, null],
+              config: {
+                custom: {
+                  filterable: true,
+                },
+              },
+            },
+          ],
+        }),
+      });
+
+      expect(within(getFooter()).getByRole('columnheader').getElementsByTagName('span')[0].textContent).toEqual('4');
+    });
+
+    it('should show count of rows when `count rows` is selected', async () => {
+      getTestContext({
+        footerOptions: { show: true, reducer: ['count'], countRows: true },
+        data: toDataFrame({
+          name: 'A',
+          fields: [
+            {
+              name: 'number1',
+              type: FieldType.number,
+              values: [1, 1, 1, 2, null],
+              config: {
+                custom: {
+                  filterable: true,
+                },
+              },
+            },
+          ],
+        }),
+      });
+
+      expect(within(getFooter()).getByRole('columnheader').getElementsByTagName('span')[0].textContent).toEqual(
+        'Count:'
+      );
+      expect(within(getFooter()).getByRole('columnheader').getElementsByTagName('span')[1].textContent).toEqual('5');
+    });
+
+    it('should show correct counts when turning `count rows` on and off', async () => {
+      const { rerender } = getTestContext({
+        footerOptions: { show: true, reducer: ['count'], countRows: true },
+        data: toDataFrame({
+          name: 'A',
+          fields: [
+            {
+              name: 'number1',
+              type: FieldType.number,
+              values: [1, 1, 1, 2, null],
+              config: {
+                custom: {
+                  filterable: true,
+                },
+              },
+            },
+          ],
+        }),
+      });
+
+      expect(within(getFooter()).getByRole('columnheader').getElementsByTagName('span')[0].textContent).toEqual(
+        'Count:'
+      );
+      expect(within(getFooter()).getByRole('columnheader').getElementsByTagName('span')[1].textContent).toEqual('5');
+
+      const onSortByChange = jest.fn();
+      const onCellFilterAdded = jest.fn();
+      const onColumnResize = jest.fn();
+      const props: Props = {
+        ariaLabel: 'aria-label',
+        data: getDefaultDataFrame(),
+        height: 600,
+        width: 800,
+        onSortByChange,
+        onCellFilterAdded,
+        onColumnResize,
+      };
+
+      const propOverrides = {
+        footerOptions: { show: true, reducer: ['count'], countRows: false },
+        data: toDataFrame({
+          name: 'A',
+          fields: [
+            {
+              name: 'number',
+              type: FieldType.number,
+              values: [1, 1, 1, 2, null],
+              config: {
+                custom: {
+                  filterable: true,
+                },
+              },
+            },
+          ],
+        }),
+      };
+
+      Object.assign(props, propOverrides);
+
+      rerender(<Table {...props} />);
+
+      expect(within(getFooter()).getByRole('columnheader').getElementsByTagName('span')[0].textContent).toEqual('4');
+    });
+  });
+
   describe('when mounted with data and sub-data', () => {
     it('then correct rows should be rendered and new table is rendered when expander is clicked', () => {
       getTestContext({

packages/grafana-ui/src/components/Table/Table.tsx

@@ -12,7 +12,7 @@ import {
 import usePrevious from 'react-use/lib/usePrevious';
 import { VariableSizeList } from 'react-window';
 
-import { DataFrame, getFieldDisplayName, Field } from '@grafana/data';
+import { DataFrame, getFieldDisplayName, Field, ReducerID } from '@grafana/data';
 
 import { useStyles2, useTheme2 } from '../../themes';
 import { CustomScrollbar } from '../CustomScrollbar/CustomScrollbar';
@@ -188,10 +188,27 @@ export const Table = memo((props: Props) => {
     return Array(data.length).fill(0);
   }, [data]);
 
+  const isCountRowsSet = Boolean(
+    footerOptions?.countRows &&
+      footerOptions.reducer &&
+      footerOptions.reducer.length &&
+      footerOptions.reducer[0] === ReducerID.count
+  );
+
   // React-table column definitions
   const memoizedColumns = useMemo(
-    () => getColumns(data, width, columnMinWidth, expandedIndexes, setExpandedIndexes, !!subData?.length, footerItems),
-    [data, width, columnMinWidth, footerItems, subData, expandedIndexes]
+    () =>
+      getColumns(
+        data,
+        width,
+        columnMinWidth,
+        expandedIndexes,
+        setExpandedIndexes,
+        !!subData?.length,
+        footerItems,
+        isCountRowsSet
+      ),
+    [data, width, columnMinWidth, footerItems, subData, expandedIndexes, isCountRowsSet]
   );
 
   // Internal react table state reducer
@@ -244,17 +261,24 @@ export const Table = memo((props: Props) => {
       return;
     }
 
-    if (footerOptions.show) {
-      setFooterItems(
-        getFooterItems(
-          headerGroups[0].headers as unknown as Array<{ field: Field }>,
-          createFooterCalculationValues(rows),
-          footerOptions,
-          theme
-        )
-      );
-    } else {
+    if (!footerOptions.show) {
       setFooterItems(undefined);
+      return;
+    }
+
+    const footerItems = getFooterItems(
+      headerGroups[0].headers as unknown as Array<{ field: Field }>,
+      createFooterCalculationValues(rows),
+      footerOptions,
+      theme
+    );
+
+    if (isCountRowsSet) {
+      const footerItemsCountRows: FooterItem[] = new Array(footerItems.length).fill(undefined);
+      footerItemsCountRows[0] = data.length.toString();
+      setFooterItems(footerItemsCountRows);
+    } else {
+      setFooterItems(footerItems);
     }
     // eslint-disable-next-line react-hooks/exhaustive-deps
   }, [footerOptions, theme, state.filters, data]);

packages/grafana-ui/src/components/Table/types.ts

@@ -50,4 +50,5 @@ export interface TableFooterCalc {
   reducer: string[]; // actually 1 value
   fields?: string[];
   enablePagination?: boolean;
+  countRows?: boolean;
 }

packages/grafana-ui/src/components/Table/utils.tsx

@@ -68,7 +68,8 @@ export function getColumns(
   expandedIndexes: Set<number>,
   setExpandedIndexes: (indexes: Set<number>) => void,
   expander: boolean,
-  footerValues?: FooterItem[]
+  footerValues?: FooterItem[],
+  isCountRowsSet?: boolean
 ): GrafanaTableColumn[] {
   const columns: GrafanaTableColumn[] = expander
     ? [
@@ -134,7 +135,7 @@ export function getColumns(
       minWidth: fieldTableOptions.minWidth ?? columnMinWidth,
       filter: memoizeOne(filterByValue(field)),
       justifyContent: getTextAlign(field),
-      Footer: getFooterValue(fieldIndex, footerValues),
+      Footer: getFooterValue(fieldIndex, footerValues, isCountRowsSet),
     });
   }
 

public/app/plugins/panel/table/models.gen.ts

@@ -27,6 +27,7 @@ export const defaultPanelOptions: PanelOptions = {
   footer: {
     show: false,
     reducer: [],
+    countRows: false,
   },
 };
 

public/app/plugins/panel/table/module.tsx

@@ -131,6 +131,14 @@ export const plugin = new PanelPlugin<PanelOptions, TableFieldOptions>(TablePane
         defaultValue: [ReducerID.sum],
         showIf: (cfg) => cfg.footer?.show,
       })
+      .addBooleanSwitch({
+        path: 'footer.countRows',
+        category: [footerCategory],
+        name: 'Count rows',
+        description: 'Display a single count for all data rows',
+        defaultValue: defaultPanelOptions.footer?.countRows,
+        showIf: (cfg) => cfg.footer?.reducer?.length === 1 && cfg.footer?.reducer[0] === ReducerID.count,
+      })
       .addMultiSelect({
         path: 'footer.fields',
         category: [footerCategory],
@@ -156,7 +164,9 @@ export const plugin = new PanelPlugin<PanelOptions, TableFieldOptions>(TablePane
           },
         },
         defaultValue: '',
-        showIf: (cfg) => cfg.footer?.show,
+        showIf: (cfg) =>
+          (cfg.footer?.show && !cfg.footer?.countRows) ||
+          (cfg.footer?.reducer?.length === 1 && cfg.footer?.reducer[0] !== ReducerID.count),
       })
       .addCustomEditor({
         id: 'footer.enablePagination',