Cannot search sxatags to find related items - 'undefined field sxatags'

Question

Sitecore 9.3 with SXA. I'm trying to utilise sxa tags from the inherited _Taggable template to programmatically find related items with similar tags to the context item.

That SXA template is /sitecore/templates/Foundation/Experience Accelerator/Taxonomy/_Taggable

which looks like this

Looking in SOLR schema shows sxatags indexed as 'sxatags_sm'

I have an search class inheriting from SearchResultItem.

public class EventSearchResultItem : SearchResultItem
    {
        [Sitecore.ContentSearch.IndexField("eventstartdatetime")]
        public DateTime EventStartDate { get; set; }

        [Sitecore.ContentSearch.IndexField("sxatags_sm")]
        public virtual IEnumerable<ID> Tags { get; set; }
    }

I'm using the following predicate setup to locate future events with similar tags.

                var contentStartItem = Sitecore.Context.Database.GetItem(Sitecore.Context.Site.ContentStartPath);

                var tagsPredicate = PredicateBuilder.True<EventSearchResultItem>(); 
                Sitecore.Data.Fields.MultilistField multiListField = Sitecore.Context.Item.Fields[Constants.Event.Fields.TAGS_ID];
                if (multiListField != null)
                {
                    foreach (ID id in multiListField.TargetIDs)
                    {
                        tagsPredicate = tagsPredicate.Or(x => x.Tags.Contains(id));
                    }
                }

                var mainPredicate = PredicateBuilder.True<EventSearchResultItem>();
                mainPredicate = mainPredicate.And(p => p.Paths.Contains(contentStartItem.ID));
                mainPredicate = mainPredicate.And(p => p.TemplateId == Constants.Event.Template.TEMPLATE_ID);
                mainPredicate = mainPredicate.And(p => p.EventStartDate > DateTime.Now.AddDays(-1)); 
                mainPredicate = mainPredicate.And(tagsPredicate);

                var indexResolver = ServiceLocator.ServiceProvider.GetService<IIndexResolver>();
                using (var searchContext = indexResolver.ResolveIndex(Sitecore.Context.Item).CreateSearchContext())
                {
                    var searchQuery = searchContext.GetQueryable<EventSearchResultItem>().Where(mainPredicate);
                    var results = searchQuery
                        .Take(numberOfResults)
                        .OrderByDescending(p => p.EventStartDate)
                        .GetResults();

                    relatedEvents.Events = string.Join("|", results.Hits.Select(x => x.Document.ItemId));
                }

When this runs, I'm seeing this in SOLR logs ( http://localhost:44011/solr/#/~logging )

org.apache.solr.common.SolrException: undefined field sxatags

Questions

1. Why is this still looking up 'sxatags' when I have defined the field as 'sxatags_sm' ?
2. Is this a valid approach for looking up related item tags?
3. How do I fix it!

Answer 1

When the content search API resolves your Linq code to a Solr query, unless the field is a known named field, then Sitecore will attempt to correct any suffix on the IndexField attribute. This is how it solves the problem that Solr requires a defined schema, so Sitecore adds dynamic fields to the schema and uses the suffix to define the data type.

_sm is defined as a multivalued string

So you just need a couple of changes to your model definition. Change the IndexField to just sxatags and then you need to use a type converter to tell the ContentSearchApi how to convert the Solr data into your model. You can use the IndeFieldEnumerableConverter for this:

public class EventSearchResultItem : SearchResultItem
{
    [Sitecore.ContentSearch.IndexField("eventstartdatetime")]
    public DateTime EventStartDate { get; set; }

    [Sitecore.ContentSearch.IndexField("sxatags")]
    [TypeConverter(typeof (IndexFieldEnumerableConverter))]
    public virtual IEnumerable<ID> Tags { get; set; }
}

For an example of this pattern, look in the SearchResultItem.cs class at the Semantics property (Standard Sitecore Tags field). It is defined like this:

[IndexField("__semantics")]
[DataMember]
[TypeConverter(typeof (IndexFieldEnumerableConverter))]
public virtual IEnumerable<ID> Semantics { get; set; }