see on GitHub

Session: How to Use MoreLikeThis

MoreLikeThis is available through query extension methods and will return similar documents according to the provided criteria and options.

Syntax

IRavenQueryable<T> MoreLikeThis<T>(MoreLikeThisBase moreLikeThis);

IRavenQueryable<T> MoreLikeThis<T>(Action<IMoreLikeThisBuilder<T>> builder);
Parameters
moreLikeThis MoreLikeThisBase Defines the type of MoreLikeThis that should be executed
builder Action<IMoreLikeThisFactory<T>> Builder with fluent API that constructs the MoreLikeThisBase instance

Builder

IMoreLikeThisOperations<T> UsingAnyDocument();

IMoreLikeThisOperations<T> UsingDocument(string documentJson);

IMoreLikeThisOperations<T> UsingDocument(Expression<Func<T, bool>> predicate);

IMoreLikeThisOperations<T> WithOptions(MoreLikeThisOptions options);
Parameters
documentJson string Inline JSON document that will be used as a base for operation
predicate Expression<Func<T, bool>> Filtering expression utilized to find a document that will be used as a base for operation
options MoreLikeThisOptions Non-default options that should be used for operation

Options

public int? MinimumTermFrequency { get; set; } = 2;

public int? MaximumQueryTerms { get; set; } = 25;

public int? MaximumNumberOfTokensParsed { get; set; } = 5000;

public int? MinimumWordLength { get; set; } = 0;

public int? MaximumWordLength { get; set; } = 0;

public int? MinimumDocumentFrequency { get; set; } = 5;

public int? MaximumDocumentFrequency { get; set; } = int.MaxValue;

public int? MaximumDocumentFrequencyPercentage { get; set; }

public bool? Boost { get; set; } = false;

public float? BoostFactor { get; set; } = 1;

public string StopWordsDocumentId { get; set; }

public string[] Fields { get; set; }
Options
MinimumTermFrequency int? Ignores terms with less than this frequency in the source doc
MaximumQueryTerms int? Returns a query with no more than this many terms
MaximumNumberOfTokensParsed int? The maximum number of tokens to parse in each example doc field that is not stored with TermVector support
MinimumWordLength int? Ignores words less than this length or, if 0, then this has no effect
MaximumWordLength int? Ignores words greater than this length or if 0 then this has no effect
MinimumDocumentFrequency int? Ignores words which do not occur in at least this many documents
MaximumDocumentFrequency int? Ignores words which occur in more than this many documents
MaximumDocumentFrequencyPercentage int? Ignores words which occur in more than this percentage of documents
Boost bool? Boost terms in query based on score
BoostFactor float? Boost factor when boosting based on score
StopWordsDocumentId string Document ID containing custom stop words
Fields string[] Fields to compare

Example I

// Search for similar articles to 'articles/1'
// using 'Articles/MoreLikeThis' index and search only field 'Body'
List<Article> articles = session
    .Query<Article>("Articles/MoreLikeThis")
    .MoreLikeThis(builder => builder
        .UsingDocument(x => x.Id == "articles/1")
        .WithOptions(new MoreLikeThisOptions
        {
            Fields = new[] { "Body" }
        }))
    .ToList();
// Search for similar articles to 'articles/1'
// using 'Articles/MoreLikeThis' index and search only field 'Body'
List<Article> articles = await asyncSession
    .Query<Article>("Articles/MoreLikeThis")
    .MoreLikeThis(builder => builder
        .UsingDocument(x => x.Id == "articles/1")
        .WithOptions(new MoreLikeThisOptions
        {
            Fields = new[] { "Body" }
        }))
    .ToListAsync();
from index 'Articles/MoreLikeThis' 
where morelikethis(id() = 'articles/1', '{ "Fields" : [ "Body" ] }')

Example II

// Search for similar articles to 'articles/1'
// using 'Articles/MoreLikeThis' index and search only field 'Body'
// where article category is 'IT'
List<Article> articles = session
    .Query<Article>("Articles/MoreLikeThis")
    .MoreLikeThis(builder => builder
        .UsingDocument(x => x.Id == "articles/1")
        .WithOptions(new MoreLikeThisOptions
        {
            Fields = new[] { "Body" }
        }))
    .Where(x => x.Category == "IT")
    .ToList();
// Search for similar articles to 'articles/1'
// using 'Articles/MoreLikeThis' index and search only field 'Body'
// where article category is 'IT'
List<Article> articles = await asyncSession
    .Query<Article>("Articles/MoreLikeThis")
    .MoreLikeThis(builder => builder
        .UsingDocument(x => x.Id == "articles/1")
        .WithOptions(new MoreLikeThisOptions
        {
            Fields = new[] { "Body" }
        }))
    .Where(x => x.Category == "IT")
    .ToListAsync();
from index 'Articles/MoreLikeThis' 
where morelikethis(id() = 'articles/1', '{ "Fields" : [ "Body" ] }') and Category == 'IT'

Remarks

Do not forget to add the following using statement which contains necessary extensions:

using Raven.Client.Documents;