A DD4T.net Implementation - Taxonomy Performance Issues

Retrieving Classified Items for Multiple Keywords

My intention when retrieving the classified items for a taxonomy is to resolve the entire taxonomy (i.e. all its keywords) first, and then cache it. This way, retrieving the related content for a given keyword would be very fast. I described this approach for DD4T Java in post Retrieve Classified Items for Multiple Keywords.

There is one issue with that approach in .NET -- it is not standard API and one must write their own Java Hibernate code to retrieve the classified items. In DD4T Java that is not an issue, but in DD4T .NET, exposing the custom Java logic to the .NET CLR is not easy. It would involve writing some JNI proxy classes to bridge the two virtual machines. I just don't feel like writing that code.

Enter the second best approach -- resolving classified items on-the-fly, for one keyword at the time, on demand, as described in post Taxonomy Factory.

Retrieving Large Taxonomies

Another performance issue is to retrieve large taxonomies. The API call to read entire taxonomies is TaxonomyFactory.GetTaxonomyKeywords(taxonomyUri). This is the only method on the Tridion.ContentDelivery.Taxonomies.TaxonomyFactory class that will retrieve a root Keyword with all its Parent/Child keyword properties resolved, so the taxonomy is fully navigable up and down.

However, the method above is a bottleneck for large (really large) taxonomies. Internally the method reads all keywords in the taxonomy and all their custom meta objects. This can take a significant hit on performance.

My solution for this problem was to use a discovery algorithm that would read one keyword in the taxonomy and resolve its parent keywords up to the root. Resolving means reading its custom meta and the items directly classified against it. The root keyword would be cached, together with all its discovered child keywords.

When a new keyword would be requested, first the algorithm tries to read it from the cached root keyword (as one of its possible children). If that search didn't find the keyword, we assume the keyword was not resolved yet, and the discovery process would start once again, and it would attach the new keyword at its appropriate level in the taxonomy.

Slowly and on-demand, the taxonomy structure would be created and it would consist only of the keywords that were requested. The following code shows this algorithm. Note the usage of TaxonomyFactory.GetTaxonomyKeyword() method that returns a partially resolved keyword.

using dd4t = DD4T.ContentModel;
using tridion = Tridion.ContentDelivery.Taxonomies;

public IMyKeyword ResolveKeywordLazy(dd4t.IKeyword keyword)
{
    IMyKeyword result;

    if (keyword == null)
    {
        return null;
    }

    if (keyword is IMyKeyword)
    {
        result = (IMyKeyword)keyword;
    }
    else
    {
        IMyKeyword root;
        string key = GetKey(keyword.TaxonomyId);
        CacheWrapper.TryGet(key, out root);
        if (root == null)
        {
            result = ResolveKeywordLazyRecursive(keyword, out root);
            CacheWrapper.Insert(key, root, cacheMinutes);
        }
        else
        {
            result = ResolveKeywordLazyRecursive(root, keyword);
        }
    }
    return result;
}

private IMyKeyword ResolveKeywordLazyRecursive(IMyKeyword root, dd4t.IKeyword keyword)
{
    if (keyword == null)
    {
        return null;
    }

    IMyKeyword result = GetKeywordByUri(root, keyword.Id);
    if (result == null)
    {
        tridion.Keyword tridionKeyword = taxonomyFactory.GetTaxonomyKeyword(keyword.Id);
        result = new TaxonomyConverter().ConvertToDD4T(tridionKeyword);
        IMyKeyword parent = ResolveKeywordLazyRecursive(root, result.ParentKeyword);

        if (parent != null)
        {
            result.ParentKeywords.Clear();
            result.ParentKeywords.Add(parent);
            parent.ChildKeywords.Add(result);
        }
    }

    return result;
}

private IMyKeyword ResolveKeywordLazyRecursive(dd4t.IKeyword keyword, out IMyKeyword root)
{
    if (keyword == null)
    {
        root = null;
        return null;
    }

    tridion.Keyword tridionKeyword = taxonomyFactory.GetTaxonomyKeyword(keyword.Id);
    IMyKeyword result = new TaxonomyConverter().ConvertToDD4T(tridionKeyword);
    IMyKeyword parent = ResolveKeywordLazyRecursive(result.ParentKeyword, out root);

    if (parent == null)
    {
        root = result;
    }
    else
    {
        result.ParentKeywords.Clear();
        result.ParentKeywords.Add(parent);
        parent.ChildKeywords.Add(result);
    }

    return result;
}