Hot Chocolate has a data integration for MongoDB. With this integration, you can translate paging, filtering, sorting, and projections, directly into native MongoDB queries.

You can find a example project in Hot Chocolate Examples

Get Started

To use the MongoDB integration, you need to install the package HotChocolate.Data.MongoDb.

dotnet add package HotChocolate.Data.MongoDb

MongoExecutable

The whole integration builds around IExecutable<T>. The integration provides you the extension method AsExecutable on IMongoCollection<T>, IAggregateFluent<T> and IFindFluent<T> The execution engine picks up the IExecutable and executes it efficiently. You are free to use any form of aggregation or find a pipeline before you execute AsExecutable

[UsePaging]
[UseProjection]
[UseSorting]
[UseFiltering]
public IExecutable<Person> GetPersons([Service] IMongoCollection<Person> collection)
{
    return collection.AsExecutable();
}

[UseFirstOrDefault]
public IExecutable<Person> GetPersonById(
    [Service] IMongoCollection<Person> collection,
    Guid id)
{
    return collection.Find(x => x.Id == id).AsExecutable();
}

Filtering

To use MongoDB filtering you need to register the convention on the schema builder:

services
    .AddGraphQLServer()
    .AddQueryType<Query>()
    .AddMongoDbFiltering();

To use MongoDB filtering alongside with IQueryable/IEnumerable, you have to register the MongoDB convention under a different scope. You can specify the scope on the schema builder by executing AddMongoDbFiltering("yourScope"). You then have to specify this scope on each method you use MongoDb filtering: [UseFiltering(Scope = "yourScope")] or UseFiltering(scope = "yourScope")

Your filters are now converted to BsonDocuments and applied to the executable.

GraphQL Query:

query GetPersons {
  persons(
    where: {
      name: { eq: "Yorker Shorton" }
      addresses: { some: { street: { eq: "04 Leroy Trail" } } }
    }
  ) {
    name
    addresses {
      street
      city
    }
  }
}

Mongo Query

{
  "find": "person",
  "filter": {
    "Name": { "$eq": "Yorker Shorton" },
    "Addresses": { "$elemMatch": { "Street": { "$eq": "04 Leroy Trail" } } }
  }
}

Sorting

To use MongoDB sorting you need to register the convention on the schema builder:

services
    .AddGraphQLServer()
    .AddQueryType<Query>()
    .AddMongoDbSorting();

To use MongoDB Sorting alongside with IQueryable/IEnumerable, you have to register the MongoDB convention under a different scope. You can specify the scope on the schema builder by executing AddMongoDbSorting("yourScope"). You then have to specify this scope on each method you use MongoDb Sorting: [UseSorting(Scope = "yourScope")] or UseSorting(scope = "yourScope")

Your sorting is now converted to BsonDocuments and applied to the executable.

GraphQL Query:

query GetPersons {
  persons(order: [{ name: ASC }, { mainAddress: { city: DESC } }]) {
    name
    addresses {
      street
      city
    }
  }
}

Mongo Query

{
  "find": "person",
  "filter": {},
  "sort": { "Name": 1, "MainAddress.City": -1 }
}

Projections

To use MongoDB projections you need to register the convention on the schema builder:

services
    .AddGraphQLServer()
    .AddQueryType<Query>()
    .AddMongoDbProjections();

To use MongoDB Projections alongside with IQueryable/IEnumerable, you have to register the MongoDB convention under a different scope. You can specify the scope on the schema builder by executing AddMongoDbProjections("yourScope"). You then have to specify this scope on each method you use MongoDb Projections: [UseProjections(Scope = "yourScope")] or UseProjections(scope = "yourScope")

Projections do not always lead to a performance increase. Even though MongoDB processes and transfers less data, it more often than not harms query performance. This Medium article by Tek Loon explains how and when to use projections well.

GraphQL Query:

query GetPersons {
  persons {
    name
    addresses {
      city
    }
  }
}

Mongo Query

{
  "find": "person",
  "filter": {},
  "projection": { "Addresses.City": 1, "Name": 1 }
}

Paging

The integration comes with providers for offset and cursor-based pagination

Cursor Pagination

To use cursor based pagination annoate you resolver with [UseMongoDbPaging] or .UseMongoDbPaging()

[UseMongoDbPaging]
public IExecutable<Person> GetPersons([Service] IMongoCollection<Person> collection)
{
    return collection.AsExecutable();
}

You can then execute queries like the following one:

query GetPersons {
  persons(first: 50, after: "OTk=") {
    nodes {
      name
      addresses {
        city
      }
    }
    pageInfo {
      endCursor
      hasNextPage
      hasPreviousPage
      startCursor
    }
  }
}

Offset Pagination

To use cursor based pagination annoate you resolver with [UseMongoDbPaging] or .UseMongoDbPaging()

[UseMongoDbOffsetPaging]
public IExecutable<Person> GetPersons([Service] IMongoCollection<Person> collection)
{
    return collection.AsExecutable();
}

You can then execute queries like the following one:

query GetPersons {
  persons(skip: 50, take: 50) {
    items {
      name
      addresses {
        city
      }
    }
    pageInfo {
      hasNextPage
      hasPreviousPage
    }
  }
}

FirstOrDefault / SingleOrDefault

Sometimes you may want to return only a single object of a collection. To limit the response to one element you can use the UseFirstOrDefault or UseSingleOrDefault middleware. Hot Chocolate will rewrite the type of the field from a list type to an object type.

[UseFirstOrDefault]
public IExecutable<Person> GetPersonById(
    [Service] IMongoCollection<Person> collection,
    Guid id)
{
    return collection.Find(x => x.Id == id).AsExecutable();
}