Documents have an identifier called a Reference (or just Ref). A document’s Reference is a compound value comprising its collection along with a unique document ID. A Reference is a unique identifier for the document within the scope of the database in which it is stored. The document ID is a string-encoded 64-bit integer.

try
{
    Value result = await client.Query(
        Let(
            "doc", Get(Ref(Collection("users"), "1"))
        ).In(
            Obj(
                "document", Var("doc"),
                "reference", Select("ref", Var("doc")),
                "reference collection", Select(
                    Arr("ref", "collection"),
                    Var("doc")
                ),
                "document ID", Select(
                    Arr("ref", "id"),
                    Var("doc")
                )
            )
        )
    );
    Console.WriteLine(result);
}
catch (Exception e)
{
    Console.WriteLine($"ERROR: {e.Message}");
}

ObjectV(document: ObjectV(ref: RefV(id = "1", collection = RefV(id = "users", collection = RefV(id = "collections"))),ts: LongV(1625505840300000),data: ObjectV(name: StringV(Alice Crypto),email: StringV(alice@site.example.com))),reference: RefV(id = "1", collection = RefV(id = "users", collection = RefV(id = "collections"))),reference collection: RefV(id = "users", collection = RefV(id = "collections")),document ID: StringV(1))

result, err := client.Query(
	f.Let().Bind(
		"doc", f.Get(f.Ref(f.Collection("users"), "1")),
	).In(
		f.Obj{
			"document": f.Var("doc"),
			"reference": f.Select("ref", f.Var("doc")),
			"reference collection": f.Select(
				f.Arr{"ref", "collection"},
				f.Var("doc"),
			),
			"document ID": f.Select(
				f.Arr{"ref", "id"},
				f.Var("doc"),
			),
		},
	))

if err != nil {
	fmt.Fprintln(os.Stderr, err)
} else {
	fmt.Println(result)
}

map[document:map[data:map[email:alice@site.example.com name:Alice Crypto] ref:{1 0xc0000925a0 0xc0000925a0 <nil>} ts:1625506145900000] document ID:1 reference:{1 0xc000092780 0xc000092780 <nil>} reference collection:{users 0xc000092870 0xc000092870 <nil>}]

System.out.println(
    client.query(
        Let(
            "doc", Get(Ref(Collection("users"), "1"))
        ).in(
            Obj(
                "document", Var("doc"),
                "reference", Select(Value("ref"), Var("doc")),
                "reference collection", Select(
                    Arr(Value("ref"), Value("collection")),
                    Var("doc")
                ),
                "document ID", Select(
                    Arr(Value("ref"), Value("id")),
                    Var("doc")
                )
            )
        )
    ).get());

{document: {ref: ref(id = "1", collection = ref(id = "users", collection = ref(id = "collections"))), ts: 1625506508690000, data: {name: "Alice Crypto", email: "alice@site.example.com"}}, reference: ref(id = "1", collection = ref(id = "users", collection = ref(id = "collections"))), reference collection: ref(id = "users", collection = ref(id = "collections")), document ID: "1"}

client.query(
  q.Let(
    {
      doc: q.Get(q.Ref(q.Collection('users'), '1')),
    },
    {
      document: q.Var('doc'),
      reference: q.Select('ref', q.Var('doc')),
      'reference collection': q.Select(['ref', 'collection'], q.Var('doc')),
      'document ID': q.Select(['ref', 'id'], q.Var('doc')),
    }
  )
)
.then((res) => console.log(res))
.catch((err) => console.error(
  'Error: [%s] %s: %s',
  err.name,
  err.message,
  err.errors()[0].description,
))

{
  document: {
    ref: Ref(Collection("users"), "1"),
    ts: 1625505428470000,
    data: { name: 'Alice Crypto', email: 'alice@site.example.com' }
  },
  reference: Ref(Collection("users"), "1"),
  'reference collection': Collection("users"),
  'document ID': '1'
}

result = client.query(
  q.let(
    {
      "doc": q.get(q.ref(q.collection("users"), "1")),
    },
    {
      "document": q.var("doc"),
      "reference": q.select("ref", q.var("doc")),
      "reference collection": q.select(["ref", "collection"], q.var("doc")),
      "document ID": q.select(["ref", "id"], q.var("doc")),
    }
  )
)
print(result)

{'document': {'ref': Ref(id=1, collection=Ref(id=users, collection=Ref(id=collections))), 'ts': 1625505236270000, 'data': {'name': 'Alice Crypto', 'email': 'alice@site.example.com'}}, 'reference': Ref(id=1, collection=Ref(id=users, collection=Ref(id=collections))), 'reference collection': Ref(id=users, collection=Ref(id=collections)), 'document ID': '1'}

Let(
  {
    doc: Get(Ref(Collection("users"), "1")),
  },
  {
    "document": Var("doc"),
    "reference": Select("ref", Var("doc")),
    "reference collection": Select(["ref", "collection"], Var("doc")),
    "document ID": Select(["ref", "id"], Var("doc")),
  }
)

{
  document: {
    ref: Ref(Collection("users"), "1"),
    ts: 1625504819720000,
    data: { name: 'Alice Crypto', email: 'alice@site.example.com' }
  },
  reference: Ref(Collection("users"), "1"),
  'reference collection': Collection("users"),
  'document ID': '1'
}

User-specified documents have a timestamp that identifies when the document was most recently updated. Fauna documents are versioned — each time a document is updated, a new version is stored — and the versions are distinguished using the timestamp. When a query does not specify a timestamp, the latest versions of any documents involved are used. The timestamp — returned in the ts field — is of type Long.

Documents can have an optional ttl field (meaning time-to-live), which is a Timestamp that indicates when the document should be removed. When a document is removed, the document’s existence ceases (as if it never existed); temporal queries cannot recover the document.

Documents are manipulated with the same query language functions, such as get, create, update, replace, or delete. Documents returned by queries are represented as JSON objects. Within a query, a document’s fields may be accessed using the Select function.