# Override sorting behavior

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This is the official documentation of the `@forestadmin/agent` Node.js agent.
{% endhint %}

Depending on the data source, not all fields may be sortable, or you may want to change how the native sorting works.

By using the `replaceFieldSorting` and `emulateFieldSorting` methods, you can change a single column's sorting behavior.

#### Substitution

You can also provide replacement sort clauses. In this example, we're telling Forest Admin "When a user sorts by full name, I want to sort by the last name, and then by the first name".

```javascript
collection.replaceFieldSorting('fullName', [
  { field: 'lastName', ascending: true },
  { field: 'firstName', ascending: true },
]);
```

Another very common reason is performance. For instance, with auto-incrementing ids, sorting by `creationDate` is equivalent to sorting by the primary key in reverse order.

Using sort substitution where needed can save you from adding many indexes to your database.

```javascript
// Sorting by creationDate ascending <=> Sorting by id descending
collection.replaceFieldSorting('creationDate', [{ field: 'id', ascending: false }]);
```

#### Emulation

Sorting emulation allows making any field automatically sortable. It will sort records by lexicographical order. It is a convenient way to get things working quickly for Collections that have a low number of records (in the thousands at most).

{% hint style="warning" %}
This emulation forces the Agent to retrieve all the Collection records and compute the field values for each one of them. As a consequence, sorting emulation performance cost is **linear** with the number of records in the Collection, so **activate it sparingly and with great care**.
{% endhint %}

```javascript
collection.emulateFieldSorting('fullName');
```