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;