# ServerSideDataSource

> _Since v2.0.0_

Unified data source contract for server-side data loading.

Implement `getRows` to supply root-level rows from a remote API, database,
or any asynchronous provider. The grid calls `getRows()` whenever it needs
a new block of rows (on initial load, scroll, sort change, or filter change).

`getRows` may return either a `Promise` (e.g. `fetch(url, { signal }).then(...)`)
or a Subscribable (e.g. an Angular `HttpClient` observable). With a
Subscribable, the grid unsubscribes on supersede, which natively cancels the
underlying request — no need to wire `params.signal` into anything.

Optionally implement `getChildRows` for on-demand child data (tree children,
group rows, detail panels, etc.). If child data is already embedded in
parent rows (e.g. tree nodes with inline `children` arrays), this method
is not needed.

#### Example

```typescript
// Promise / fetch
const dataSource: ServerSideDataSource = {
  async getRows(params) {
    const res = await fetch(`/api/data?start=${params.startNode}&end=${params.endNode}`, {
      signal: params.signal,
    });
    const data = await res.json();
    return { rows: data.items, totalNodeCount: data.total };
  },
};

// Angular HttpClient (Observable)
const dataSource: ServerSideDataSource = {
  getRows: (params) =>
    this.http
      .get<{ items: unknown[]; total: number }>('/api/data', { params: toHttpParams(params) })
      .pipe(map((d) => ({ rows: d.items, totalNodeCount: d.total }))),
};
```