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Querying within Child Collections

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Marten V4 greatly improved Marten's abilities to query within child collections of documents

Quantifier Operations within Child Collections

Marten supports the Any() and Contains() quantifier operations within child collections.

The following code sample demonstrates the supported Linq patterns for collection searching:

public class ClassWithChildCollections
{
    public Guid Id;

    public IList<User> Users = new List<User>();
    public Company[] Companies = new Company[0];

    public string[] Names;
    public IList<string> NameList;
    public List<string> NameList2;
}

public void searching(IDocumentStore store)
{
    using (var session = store.QuerySession())
    {
        var searchNames = new string[] { "Ben", "Luke" };

        session.Query<ClassWithChildCollections>()
            // Where collections of deep objects
            .Where(x => x.Companies.Any(_ => _.Name == "Jeremy"))

            // Where for Contains() on array of simple types
            .Where(x => x.Names.Contains("Corey"))

            // Where for Contains() on List<T> of simple types
            .Where(x => x.NameList.Contains("Phillip"))

            // Where for Contains() on IList<T> of simple types
            .Where(x => x.NameList2.Contains("Jens"))

            // Where for Any(element == value) on simple types
            .Where(x => x.Names.Any(_ => _ == "Phillip"))

            // The Contains() operator on subqueries within Any() searches
            // only supports constant array of String or Guid expressions.
            // Both the property being searched (Names) and the values
            // being compared (searchNames) need to be arrays.
            .Where(x => x.Names.Any(_ => searchNames.Contains(_)));
    }
}

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You can search on equality of multiple fields or properties within the child collection using the && operator:

var results = theSession
    .Query<Target>()
    .Where(x => x.Children.Any(_ => _.Number == 6 && _.Double == -1))
    .ToArray();

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Finally, you can query for child collections that do not contain a value:

theSession.Query<DocWithArrays>().Count(x => !x.Strings.Contains("c"))
    .ShouldBe(2);

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theSession.Query<DocWithArrays>().Count(x => !x.Strings.Contains("c"))
    .ShouldBe(2);

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Querying within Value IEnumerables

As of now, Marten allows you to do "contains" searches within Arrays, Lists & ILists of primitive values like string or numbers:

public void query_against_string_array()
{
    var doc1 = new DocWithArrays { Strings = new [] { "a", "b", "c" } };
    var doc2 = new DocWithArrays { Strings = new [] { "c", "d", "e" } };
    var doc3 = new DocWithArrays { Strings = new [] { "d", "e", "f" } };

    theSession.Store(doc1);
    theSession.Store(doc2);
    theSession.Store(doc3);

    theSession.SaveChanges();

    theSession.Query<DocWithArrays>().Where(x => x.Strings.Contains("c")).ToArray()
        .Select(x => x.Id).ShouldHaveTheSameElementsAs(doc1.Id, doc2.Id);
}

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Marten also allows you to query over IEnumerables using the Any method for equality (similar to Contains):

[Fact]
public void query_against_number_list_with_any()
{
    var doc1 = new DocWithLists { Numbers = new List<int> { 1, 2, 3 } };
    var doc2 = new DocWithLists { Numbers = new List<int> { 3, 4, 5 } };
    var doc3 = new DocWithLists { Numbers = new List<int> { 5, 6, 7 } };
    var doc4 = new DocWithLists { Numbers = new List<int> { } };

    theSession.Store(doc1, doc2, doc3, doc4);

    theSession.SaveChanges();

    theSession.Query<DocWithLists>().Where(x => x.Numbers.Any(_ => _ == 3)).ToArray()
        .Select(x => x.Id).ShouldHaveTheSameElementsAs(doc1.Id, doc2.Id);

    // Or without any predicate
    theSession.Query<DocWithLists>()
        .Count(x => x.Numbers.Any()).ShouldBe(3);
}

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As of 1.2, you can also query against the Count() or Length of a child collection with the normal comparison operators (==, >, >=, etc.):

[Fact]
public void query_against_number_list_with_count_method()
{
    var doc1 = new DocWithLists { Numbers = new List<int> { 1, 2, 3 } };
    var doc2 = new DocWithLists { Numbers = new List<int> { 3, 4, 5 } };
    var doc3 = new DocWithLists { Numbers = new List<int> { 5, 6, 7, 8 } };

    theSession.Store(doc1);
    theSession.Store(doc2);
    theSession.Store(doc3);

    theSession.SaveChanges();

    theSession.Query<DocWithLists>()
        .Single(x => x.Numbers.Count() == 4).Id.ShouldBe(doc3.Id);
}

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IsOneOf

IsOneOf() extension can be used to query for documents having a field or property matching one of many supplied values:

// Finds all SuperUser's whose role is either
// Admin, Supervisor, or Director
var users = session.Query<SuperUser>()
    .Where(x => x.Role.IsOneOf("Admin", "Supervisor", "Director"));

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To find one of for an array you can use this strategy:

// Finds all UserWithNicknames's whose nicknames matches either "Melinder" or "Norrland"

var nickNames = new[] {"Melinder", "Norrland"};

var users = session.Query<UserWithNicknames>()
    .Where(x => x.Nicknames.IsOneOf(nickNames));

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To find one of for a list you can use this strategy:

// Finds all SuperUser's whose role is either
// Admin, Supervisor, or Director
var listOfRoles = new List<string> {"Admin", "Supervisor", "Director"};

var users = session.Query<SuperUser>()
    .Where(x => x.Role.IsOneOf(listOfRoles));

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In

In() extension works exactly the same as IsOneOf(). It was introduced as syntactic sugar to ease RavenDB transition:

// Finds all SuperUser's whose role is either
// Admin, Supervisor, or Director
var users = session.Query<SuperUser>()
    .Where(x => x.Role.In("Admin", "Supervisor", "Director"));

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To find one of for an array you can use this strategy:

// Finds all UserWithNicknames's whose nicknames matches either "Melinder" or "Norrland"

var nickNames = new[] {"Melinder", "Norrland"};

var users = session.Query<UserWithNicknames>()
    .Where(x => x.Nicknames.In(nickNames));

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To find one of for a list you can use this strategy:

// Finds all SuperUser's whose role is either
// Admin, Supervisor, or Director
var listOfRoles = new List<string> {"Admin", "Supervisor", "Director"};

var users = session.Query<SuperUser>()
    .Where(x => x.Role.In(listOfRoles));

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IsSupersetOf

// Finds all Posts whose Tags is superset of
// c#, json, or postgres
var posts = theSession.Query<Post>()
    .Where(x => x.Tags.IsSupersetOf("c#", "json", "postgres"));

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IsSubsetOf

// Finds all Posts whose Tags is subset of
// c#, json, or postgres
var posts = theSession.Query<Post>()
    .Where(x => x.Tags.IsSubsetOf("c#", "json", "postgres"));

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