Boosting Sitecore Lucene Indexing Results

Question

I'm trying to implement Recommended Results feature with Sitecore lucene search for our website.

I'm thinking to implement a Tag field, and depending on the tags selected for a page item, boost the lucene content search results.

My questions are,

• How can we boost the particular search result entry on indexing time, when we indexing to lucene index ?
• if we achieve above point, how can be a particular search result entry be boosted only for a given search wording ?

Thank you.

Answer 1

If you want to boost field during the indexing time, you can use the "boost" property of field in the index configuration. For example:

Below is another solution how you can boost an item based on keywords, which user entered:

I guess you are going to use multilist type for the Tags field. The multilist field is a reference field and contains IDs of selected items. First of all, we need to implement a computed field which would store a tag title instead of ID:

    using System.Linq;
    using Sitecore.ContentSearch;
    using Sitecore.ContentSearch.ComputedFields;
    using Sitecore.Data.Items;


    namespace SearchBoosting
    {
        public class ItemTagsComputedField
        {
            public class MediaDownloadCenterGroupComputedField : IComputedIndexField
            {
                public object ComputeFieldValue(IIndexable indexable)
                {
                    Item item = indexable as SitecoreIndexableItem;
                    if (item != null)
                    {
                        //I guess the tags field will have a multilist typle. 
                        Sitecore.Data.Fields.MultilistField field = item.Fields["Item Tags"]; //Name of field with tags

                        if (field != null)
                        {
                            var items = field.GetItems();

                            return items.Select(q => q.DisplayName).ToList(); //You can use some field for getting title of tag.
                        }
                    }

                    return null;
                }

                public string FieldName { get; set; }
                public string ReturnType { get; set; }
            }
        }
    }

Then we need to add them to the index configuration. Just add the following row to the section. It will look like below:

The next step is to add a search model:

using System.Collections.Generic;
using System.ComponentModel;
using Sitecore.ContentSearch;
using Sitecore.ContentSearch.Converters;
using Sitecore.ContentSearch.SearchTypes;

namespace SearchBoosting
{
    public class BoostingExampleSearchResultItem : SearchResultItem
    {
        [IndexField("item_tags")]
        [TypeConverter(typeof(IndexFieldEnumerableConverter))]
        public virtual IEnumerable<string> Tags { get; set; }
    }
}

Now we are ready to use this field for boosting:

using System.Collections.Generic;
using System.Linq;
using Sitecore.ContentSearch;
using Sitecore.ContentSearch.Linq;
using Sitecore.ContentSearch.Linq.Utilities;
using Sitecore;


namespace SearchBoosting
{
    public class SearchBoosting
    {
        protected virtual string SearchIndexName
        {
            get
            {
                return "your_search_index";
            }
        }

        private ISearchIndex _index;
        private ISearchIndex Index
        {
            get { return _index ?? (_index = ContentSearchManager.GetIndex(SearchIndexName)); }
        }

        public SearchResults<BoostingExampleSearchResultItem> ApplySearch(List<string> keywords)
        {

            using (IProviderSearchContext searchContext = Index.CreateSearchContext())
            {
                var query = searchContext.GetQueryable<BoostingExampleSearchResultItem>(new CultureExecutionContext(Context.Language.CultureInfo));

                var predicateRoots = PredicateBuilder.True<BoostingExampleSearchResultItem>();

                if (keywords != null && keywords.Any())
                {
                    foreach (var keyword in keywords)
                    {
                        //If we want just boost some items without theirs filtering, we need to process both conditions:
                        //if item contains a tag which is equals to entered word and if it doesn't:

                        predicateRoots = predicateRoots.Or(itm => (itm.Tags.Contains(keyword)).Boost(5f));
                        predicateRoots = predicateRoots.Or(itm => (!itm.Tags.Contains(keyword)).Boost(1f));
                    }
                }

                var results = query.Where(predicateRoots).GetResults();

                return results;
            }
        }
    }
}