Downloadable rich content loads when filtering

Question

Downloadable rich content loads when filtering

I have a nested datatable using rowExpansion. Content for each nested table loads correctly when expanding a row. However, when a filter is applied to the root table, content is loaded for all nested tables. If there are a lot of lines, it kills the performance.

Note that this is not a "JSF calls getters multiple times" problem. Content for extended lines is cached in the background. It behaves as if each individual row expands before applying the filter. Please note that the filter refers only to the value property, and not to the "lines", which are rich content.

<p:dataTable value="#{backing.elements}" var="row"
  filteredValue="#{backing.elementsFiltered}">

  <p:column>
    <p:rowToggler />
  </p:column>
  <p:column headerText="Value" filterBy="#{row.value}">
    <h:outputText value="#{row.value}" />
  </p:column>

  <p:rowExpansion>
    <p:dataTable value="#{row.strings}" var="string">
      <p:column headerText="Strings">
        <h:outputText value="#{string}" />
      </p:column>
    </p:dataTable>
  </p:rowExpansion>
</p:dataTable>

Bean support:

@Named
@ViewScoped
public class Backing implements Serializable {

    private List<Element> elements;
    private List<Element> elementsFiltered;

    @PostConstruct
    public void init() {
        // Load the list of elements.
    }

    public List<Element> getElements() {
        return elements;
    }

    public List<Element> getElementsFiltered() {
        return elementsFiltered;
    }

    public void setElementsFiltered(List<Element> elementsFiltered) {
        this.elementsFiltered = elementsFiltered;
    }
}

Entity:

public class Element {

    private String value;
    private List<String> strings;

    public String getValue() {
        return value;
    }

    // This getter is called for a particular row when it is expanded.
    // But it is called for all rows when the table is filtered.
    public List<String> getStrings() {
        if (strings == null) {
            // Expensive opperation to load the strings.
        }
        return strings;
    }
}