# `type.batch_from_invalid`

A batch's `from:` is not a call of a named query giving a `Page`.

Area 12, [Jobs and events](../topics/jobs-and-events.md); not declinable; the next step is usually the agent's.

A run walks `from:` a page at a time, so it is a call of a named query
giving a `Page`; a list's query, or a page already read, is refused:


```jadpo
query first_items() -> List<Item> {
    from: Item
    order: [Item.code asc]
    limit: 10
}

action sweep_shelf() -> BatchRun {
    return batches.each(from: first_items(), each: item -> mark_seen(item))
}
```

```text
error: `batches.each`'s `from:` isn't a call of a named query giving a `Page`
 --> main.jadpo:8:31
  |
8 |     return batches.each(from: first_items(), each: item -> mark_seen(item))
  |                               ^^^^^^^^^^^^^ gives `List<Item>`
  reason: A run walks `from:` a page at a time, after the action that starts it commits: it calls a named query that gives a `Page<T>`, and each item is a `T`; the query's arguments are worked out now and saved with the run.
  next: Write `batches.each(from: <query>(...), ...)`, with a query whose result is `Page<T>` (agent)
  rule: type.batch_from_invalid
  help: https://jadpo.dev/docs/errors/type.batch_from_invalid

check failed: 1 error, 2 files
```