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Routing inference

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Routing inference

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Implicit conversion

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You can always create a routing explicitly by relying on the implicit conversion from the following types

Int32
Int64
String
Guid

Methods and Properties that take an Routing can be passed any of these types and it will be implicitly converted to an instance of Routing

Routing routingFromInt = 1;
Routing routingFromLong = 2L;
Routing routingFromString = "hello-world";
Routing routingFromGuid = new Guid("D70BD3CF-4E38-46F3-91CA-FCBEF29B148E");

Expect(1).WhenSerializing(routingFromInt);
Expect(2).WhenSerializing(routingFromLong);
Expect("hello-world").WhenSerializing(routingFromString);
Expect("d70bd3cf-4e38-46f3-91ca-fcbef29b148e").WhenSerializing(routingFromGuid);

Inferring from a type

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The real power of the Routing is in the inference rules (the default inferred routing for an object will be null). Lets look at an example of this given the following POCO:

class MyDTO
{
    public Guid Routing { get; set; }
    public string Name { get; set; }
    public string OtherName { get; set; }
}

By default NEST will try to find a property called Routing on the class using reflection and create a cached delegate based on the property getter

var dto = new MyDTO
{
    Routing = new Guid("D70BD3CF-4E38-46F3-91CA-FCBEF29B148E"),
    Name = "x",
    OtherName = "y"
};
Expect(null).WhenInferringRoutingOn(dto);

Using connection settings, you can specify a property that NEST should use to infer Routing for the document. Here we instruct NEST to infer the Routing for MyDTO based on its Name property

WithConnectionSettings(x => x
    .DefaultMappingFor<MyDTO>(m => m
        .RoutingProperty(p => p.Name)
    )
).Expect("x").WhenInferringRoutingOn(dto);

Inference rules are cached per ConnectionSettings instance.

Because the cache is per ConnectionSettings instance, we can create another ConnectionSettings instance with different inference rules

WithConnectionSettings(x => x
    .DefaultMappingFor<MyDTO>(m => m
        .RoutingProperty(p => p.OtherName)
    )
).Expect("y").WhenInferringRoutingOn(dto);

JoinField

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If your class has a property of type JoinField, NEST will automatically infer the parentid as the routing value.

The name of this property can be anything. Be sure the read the section on Parent/Child relationships to get a complete walkthrough on using Parent Child joins with NEST.

class MyOtherDTO
{
    public JoinField SomeJoinField { get; set; }
    public Guid Id { get; set; }
    public string Name { get; set; }
    public string OtherName { get; set; }
}

here we link this instance of MyOtherDTO with its parent id "8080"

var dto = new MyOtherDTO
{
    SomeJoinField = JoinField.Link<MyOtherDTO>("8080"),
    Id = new Guid("D70BD3CF-4E38-46F3-91CA-FCBEF29B148E"),
    Name = "x",
    OtherName = "y"
};
Expect("8080").WhenInferringRoutingOn(dto);

Here we link this instance as the root (parent) of the relation. NEST infers that the default routing for this instance should be the Id of the document itself.

dto = new MyOtherDTO
{
    SomeJoinField = JoinField.Root<MyOtherDTO>(),
    Id = new Guid("D70BD3CF-4E38-46F3-91CA-FCBEF29B148E"),
    Name = "x",
    OtherName = "y"
};
Expect("d70bd3cf-4e38-46f3-91ca-fcbef29b148e").WhenInferringRoutingOn(dto);

Precedence of ConnectionSettings

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The routing property configured on ConnectionSettings always takes precedence.

WithConnectionSettings(x => x
    .DefaultMappingFor<MyOtherDTO>(m => m
        .RoutingProperty(p => p.OtherName)
    )
).Expect("y").WhenInferringRoutingOn(dto);

class BadDTO
        {
public JoinField SomeJoinField { get; set; }
public JoinField AnotherJoinField { get; set; }
public string ParentName { get; set; }
        }

A class cannot contain more than one property of type JoinField, an exception is thrown in this case

var dto = new BadDTO
{
    SomeJoinField = JoinField.Link<MyOtherDTO>("8080"),
    AnotherJoinField = JoinField.Link<MyOtherDTO>("8081"),
    ParentName = "my-parent"
};
Action resolve = () => Expect("8080").WhenInferringRoutingOn(dto);
resolve.ShouldThrow<ArgumentException>().WithMessage("BadDTO has more than one JoinField property");

unless you configure the ConnectionSettings to use an alternate property:

WithConnectionSettings(x => x
    .DefaultMappingFor<BadDTO>(m => m
        .RoutingProperty(p => p.ParentName)
    )
).Expect("my-parent").WhenInferringRoutingOn(dto);

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