Create a data model that uses embedded documents to describe a one-to-many relationship between connected data. Embedding connected data in a single document can reduce the number of read operations required to obtain data. In general, structure your schema so your application receives all of its required information in a single read operation. For example, you can use the the embedded one-to-many model to describe the following relationships:
- Country to major cities
- Author to books
- Student to classes
Example
The example schema contains three entities, with address one and address two
belonging to the same patron:
// patron document
{
_id: "joe",
name: "Joe Bookreader"
}
// address one
{
street: "123 Fake Street",
city: "Faketon",
state: "MA",
zip: "12345"
}
// address two
{
street: "1 Some Other Street",
city: "Boston",
state: "MA",
zip: "12345"
}Embedded Document Pattern
In this example the application needs to display information for the patron
and both address objects on a single page. To allow your application to retrieve all necessary information with a single query, embed the address one
and address two information inside of the patron document:
{
_id: "joe",
name: "Joe Bookreader",
addresses: [
{
street: "123 Fake Street",
city: "Faketon",
state: "MA",
zip: "12345"
},
{
street: "1 Some Other Street",
city: "Boston",
state: "MA",
zip: "12345"
}
]
}