Custom Facet Sort

[nightowl888]

Custom Facet Sort

[NightOwl888]

As mentioned in the wiki, all of the interfaces were renamed to start with "I" to follow the .NET conventions. So the equivalent of ComparatorFactory in Java is IComparatorFactory in .NET.

There is a unit test that demonstrates how to build a custom sort. Here is the relevant source.

[Test]
public void TestCustomFacetSort()
{
    BrowseRequest req = new BrowseRequest();
    FacetSpec numberSpec = new FacetSpec();
    numberSpec.CustomComparatorFactory = new TestCustomFacetSortComparatorFactory();

    numberSpec.OrderBy = FacetSpec.FacetSortSpec.OrderByCustom;
    numberSpec.MaxCount = 3;
    req.SetFacetSpec("number", numberSpec);

    var answer = new Dictionary<string, IEnumerable<BrowseFacet>>()
    {
        { "number", new BrowseFacet[] { new BrowseFacet("2130", 1), new BrowseFacet("1013", 1), new BrowseFacet("0913", 1) } }          
    };

    DoTest(req, 7, answer, null);

    numberSpec.OrderBy = FacetSpec.FacetSortSpec.OrderValueAsc;
    answer = new Dictionary<string, IEnumerable<BrowseFacet>>()
    {
        { "number", new BrowseFacet[] { new BrowseFacet("0005", 1), new BrowseFacet("0010", 1), new BrowseFacet("0011", 1) } }          
    };

    DoTest(req, 7, answer, null);
}

private class TestCustomFacetSortComparatorFactory : IComparatorFactory
{

    public IComparer<int> NewComparator(IFieldValueAccessor fieldValueAccessor, BigSegmentedArray counts)
    {
        return new TestCustomFacetSortIntComparator(fieldValueAccessor, counts);
    }

    public IComparer<BrowseFacet> NewComparator()
    {
        return new TestCustomFacetSortBrowseFacetComparator();
    }

    public class TestCustomFacetSortIntComparator : IComparer<int>
    {
        private readonly IFieldValueAccessor fieldValueAccessor;
        private readonly BigSegmentedArray counts;

        public TestCustomFacetSortIntComparator(IFieldValueAccessor fieldValueAccessor, BigSegmentedArray counts)
        {
            this.fieldValueAccessor = fieldValueAccessor;
            this.counts = counts;
        }

        public int Compare(int v1, int v2)
        {
            var size1 = (int)this.fieldValueAccessor.GetRawValue(v1);
            var size2 = (int)this.fieldValueAccessor.GetRawValue(v2);

            int val = size1 - size2;
            if (val == 0)
            {
                val = counts.Get(v1) - counts.Get(v2);
            }
            return val;
        }
    }

    public class TestCustomFacetSortBrowseFacetComparator : IComparer<BrowseFacet>
    {
        public int Compare(BrowseFacet o1, BrowseFacet o2)
        {
            int v1 = Convert.ToInt32(o1.Value);
            int v2 = Convert.ToInt32(o2.Value);
            int val = v2 - v1;
            if (val == 0)
            {
                val = o2.FacetValueHitCount - o1.FacetValueHitCount;
            }
            return val;
        }
    }
}

And the IComparatorFactory is now as follows (with documentation):

/// <summary>
/// Comparator for custom sorting a facet value.
/// author jwang
/// </summary>
public interface IComparatorFactory
{
    ///<summary>Providers a Comparator from field values and counts. This is called within a browse. </summary>
    ///<param name="fieldValueAccessor"> accessor for field values </param>
    ///<param name="counts"> hit counts </param>
    ///<returns> Comparator instance </returns>
    IComparer<int> NewComparator(IFieldValueAccessor fieldValueAccessor, BigSegmentedArray counts);

    ///<summary>Providers a Comparator. This is called when doing a merge across browses. </summary>
    ///<returns> Comparator instance </returns>
    IComparer<BrowseFacet> NewComparator();
}

[NightOwl888]

Note that the return type of the IComparatorFactory is the .NET IComparer<T> type, and works the same way as specified on MSDN.

[dtosato]

Okey, it works!