If a repository item property references a large sub-tree of items, it can be inefficient to retrieve and cache the child items each time the parent item is cached. In this case, you can specify to cache only the repository IDs of the child items, by setting the property’s cacheReferencesById to true. For example:

<property name="childProducts" ...>
...
    <attribute name="cacheReferencesById" value="true"/>
</property>