Can you eager load field on an element matched by route?

[a-solaris]

Eager loading is a must-have in any site, no matter the complexity, but I was wondering how to deal with eager loading, when the element is matched by routing.

Say I have an Entry with multiple element custom fields, often relating more elements with their own relations. In a template matched by a route, the element is supplied via entry variable, preventing me from supplying the with value (Craft 4).

Is it possible or feasible to tap into this process? Or is the best approach to take take the id from the loaded element and query it again, supplying the with value?

[brandonkelly]

There’s no need to eager-load the matched entry or its immediate relations, since none of those will be n+1 queries. But if its relations have nested relations, you can eager-load those.

{% set relatedEntries = entry.myEntriesField
  .with('myAssetsField')
  .all() %}

{% for relatedEntry in relatedEntries %}
  {% for asset in relatedEntry.myAssetsField %}
    ...
  {% endfor %}
{% endfor %}

Or in Craft 5 with lazy eager-loading:

{% for relatedEntry in entry.relatedEntries %}
  {% for asset in relatedEntry.myAssetsField.eagerly() %}
    ...
  {% endfor %}
{% endfor %}