# Scopes

How a scope decides which rows a client sees, and how scoped subscriptions
stay in sync.

Sometimes a page wants a scoped view of a table. The comments for a given post,
the messages in a given chat room, the tasks for a given project. A scoped
LiveTable declares the partition column and binds a value per request.

```ts
let comments = new LiveTable<Comment>({ scope: "roomId" });

export default function route(req) {
  return new html({ comments: comments.scope(req.params.id) });
}
```

The scope value is any string produced on the server: a URL parameter, the
current user id, a team id. To scope a table to the authenticated user, pass
`session.getOrThrow("userId")` after a logged-in check.

```ts
let transfers = new LiveTable<Transfer>({ scope: "userId" });

export default function route(req) {
  session.isLoggedInOrThrow();

  return new html({ transfers: transfers.scope(session.getOrThrow("userId")) });
}
```

What `.scope(value)` does:

- Each scope value gets its own pub/sub channel, so a mutation in one scope only
  broadcasts to watchers of that same scope.
- Auto-SELECT adds `where <scope_col> = $1`.
- Optimistic inserts auto-fill the scope column when omitted.
- Every mutation is validated against the bound scope value. Mismatches throw
  `ScopeMismatchError`.

Scope columns are immutable on existing rows. To move a row between scopes,
delete and re-insert.

`.scope()` is server-only. Bind the scope value in the route handler, and the
browser receives the already-scoped instance.