Class DocumentReference (2.17.0) 

DocumentReference(*path, **kwargs)

A reference to a document in a Firestore database.

The document may already exist or can be created by this class.

Parameters
Name Description
path Tuple[str, ...]

The components in the document path. This is a series of strings representing each collection and sub-collection ID, as well as the document IDs for any documents that contain a sub-collection (as well as the base document).
kwargs dict

The keyword arguments for the constructor. The only supported keyword is client and it must be a Client. It represents the client that created this document reference.

Methods

collections

collections(
    page_size: typing.Optional[int] = None,
    retry: google.api_core.retry.retry_unary.Retry = _MethodDefault._DEFAULT_VALUE,
    timeout: typing.Optional[float] = None,
) -> typing.Generator[typing.Any, typing.Any, None]

List subcollections of the current document.

Parameters
Name Description
page_size Optional[int]]

The maximum number of collections in each page of results from this request. Non-positive values are ignored. Defaults to a sensible value set by the API.
retry google.api_core.retry.Retry

Designation of what errors, if any, should be retried. Defaults to a system-specified policy.
timeout float

The timeout for this request. Defaults to a system-specified value.
Returns
Type Description
Sequence[CollectionReference] iterator of subcollections of the current document. If the document does not exist at the time of snapshot, the iterator will be empty

create

create(
    document_data: dict,
    retry: google.api_core.retry.retry_unary.Retry = _MethodDefault._DEFAULT_VALUE,
    timeout: typing.Optional[float] = None,
) -> google.cloud.firestore_v1.types.write.WriteResult

Create a document in the Firestore database.

document_data = {"a": 1, "b": {"c": "Two"}} document.get().to_dict() is None # does not exist True document.create(document_data) document.get().to_dict() == document_data # exists True

Parameters
Name Description
document_data dict

Property names and values to use for creating a document.
retry google.api_core.retry.Retry

Designation of what errors, if any, should be retried. Defaults to a system-specified policy.
timeout float

The timeout for this request. Defaults to a system-specified value.
Exceptions
Type Description
google.cloud.exceptions.Conflict If the document already exists.
Returns
Type Description
WriteResult The write result corresponding to the committed document. A write result contains an update_time field.

delete

delete(
    option: typing.Optional[google.cloud.firestore_v1._helpers.WriteOption] = None,
    retry: google.api_core.retry.retry_unary.Retry = _MethodDefault._DEFAULT_VALUE,
    timeout: typing.Optional[float] = None,
) -> google.protobuf.timestamp_pb2.Timestamp

Delete the current document in the Firestore database.

Parameters
Name Description
option Optional[WriteOption]

A write option to make assertions / preconditions on the server state of the document before applying changes.
retry google.api_core.retry.Retry

Designation of what errors, if any, should be retried. Defaults to a system-specified policy.
timeout float

The timeout for this request. Defaults to a system-specified value.
Returns
Type Description
google.protobuf.timestamp_pb2.Timestamp The time that the delete request was received by the server. If the document did not exist when the delete was sent (i.e. nothing was deleted), this method will still succeed and will still return the time that the request was received by the server.

get

get(
    field_paths: typing.Optional[typing.Iterable[str]] = None,
    transaction=None,
    retry: google.api_core.retry.retry_unary.Retry = _MethodDefault._DEFAULT_VALUE,
    timeout: typing.Optional[float] = None,
) -> google.cloud.firestore_v1.base_document.DocumentSnapshot

Retrieve a snapshot of the current document.

See xref_field_path for more information on field paths.

If a transaction is used and it already has write operations added, this method cannot be used (i.e. read-after-write is not allowed).

Parameters
Name Description
field_paths Optional[Iterable[str, ...]]

An iterable of field paths (.-delimited list of field names) to use as a projection of document fields in the returned results. If no value is provided, all fields will be returned.
retry google.api_core.retry.Retry

Designation of what errors, if an y, should be retried. Defaults to a system-specified policy.
timeout float

The timeout for this request. Defaults to a system-specified value.
transaction Optional[Transaction]

An existing transaction that this reference will be retrieved in.
Returns
Type Description
DocumentSnapshot A snapshot of the current document. If the document does not exist at the time of the snapshot is taken, the snapshot's reference, data, update_time, and create_time attributes will all be None and its exists attribute will be False.

on_snapshot

on_snapshot(callback: typing.Callable) -> google.cloud.firestore_v1.watch.Watch

Watch this document.

This starts a watch on this document using a background thread. The provided callback is run on the snapshot.

Parameter
Name Description
callback Callable[[DocumentSnapshot], NoneType] Example: .. code-block:: python from google.cloud import firestore_v1 db = firestore_v1.Client() collection_ref = db.collection(u'users') def on_snapshot(document_snapshot, changes, read_time): doc = document_snapshot print(u'{} => {}'.format(doc.id, doc.to_dict())) doc_ref = db.collection(u'users').document( u'alovelace' + unique_resource_id()) # Watch this document doc_watch = doc_ref.on_snapshot(on_snapshot) # Terminate this watch doc_watch.unsubscribe()

a callback to run when a change occurs

set

set(
    document_data: dict,
    merge: bool = False,
    retry: google.api_core.retry.retry_unary.Retry = _MethodDefault._DEFAULT_VALUE,
    timeout: typing.Optional[float] = None,
) -> google.cloud.firestore_v1.types.write.WriteResult

Create / replace / merge a document in the Firestore database.

  • To "upsert" a document (create if it doesn't exist, replace completely if it does), leave the merge argument at its default:

    document_data = {"a": 1, "b": {"c": "Two"}} document.get().to_dict() is None # document exists False document.set(document_data) document.get().to_dict() == document_data # exists True

  • To "merge" document_data with an existing document (creating if the document does not exist), pass merge as True`:

    document_data = {"a": 1, "b": {"c": "Two"}} document.get().to_dict() == {"d": "Three", "b": {}} # exists document.set(document_data, merge=True) document.get().to_dict() == {"a": 1, "d": "Three", "b": {"c": "Two"}} True

    In this case, existing documents with top-level keys which are not present in document_data ("d") will preserve the values of those keys.

  • To merge only specific fields of document_data with existing documents (creating if the document does not exist), pass merge as a list of field paths:

document_data = {"a": 1, "b": {"c": "Two"}} document.get().to_dict() == {"b": {"c": "One", "d": "Four" }} # exists True document.set(document_data, merge=["b.c"]) document.get().to_dict() == {"b": {"c": "Two", "d": "Four" }} True

For more information on field paths, see xref_field_path.

Parameters
Name Description
document_data dict

Property names and values to use for replacing a document.
merge Optional[bool] or Optional[List

If True, apply merging instead of overwriting the state of the document.
retry google.api_core.retry.Retry

Designation of what errors, if any, should be retried. Defaults to a system-specified policy.
timeout float

The timeout for this request. Defaults to a system-specified value.
Returns
Type Description
WriteResult The write result corresponding to the committed document. A write result contains an update_time field.

update

update(
    field_updates: dict,
    option: typing.Optional[google.cloud.firestore_v1._helpers.WriteOption] = None,
    retry: google.api_core.retry.retry_unary.Retry = _MethodDefault._DEFAULT_VALUE,
    timeout: typing.Optional[float] = None,
) -> google.cloud.firestore_v1.types.write.WriteResult

Update an existing document in the Firestore database.

By default, this method verifies that the document exists on the server before making updates. A write option can be specified to override these preconditions.

Each key in field_updates can either be a field name or a field path (For more information on field paths, see xref_field_path.) To illustrate this, consider a document with

>>> snapshot = document.get()
>>> snapshot.to_dict()
{
    'foo': {
        'bar': 'baz',
    },
    'other': True,
}

stored on the server. If the field name is used in the update:

>>> field_updates = {
...     'foo': {
...         'quux': 800,
...     },
... }
>>> document.update(field_updates)

then all of foo will be overwritten on the server and the new value will be

>>> snapshot = document.get()
>>> snapshot.to_dict()
{
    'foo': {
        'quux': 800,
    },
    'other': True,
}

On the other hand, if a .-delimited field path is used in the update:

>>> field_updates = {
...     'foo.quux': 800,
... }
>>> document.update(field_updates)

then only foo.quux will be updated on the server and the field foo.bar will remain intact:

>>> snapshot = document.get()
>>> snapshot.to_dict()
{
    'foo': {
        'bar': 'baz',
        'quux': 800,
    },
    'other': True,
}


>>> field_updates = {
...     'other': firestore.DELETE_FIELD,
... }
>>> document.update(field_updates)

would update the value on the server to:

>>> snapshot = document.get()
>>> snapshot.to_dict()
{
    'foo': {
        'bar': 'baz',
    },
}

To set a field to the current time on the server when the update is received, use the xref_SERVER_TIMESTAMP sentinel. Sending

>>> field_updates = {
...     'foo.now': firestore.SERVER_TIMESTAMP,
... }
>>> document.update(field_updates)

would update the value on the server to:

>>> snapshot = document.get()
>>> snapshot.to_dict()
{
    'foo': {
        'bar': 'baz',
        'now': datetime.datetime(2012, ...),
    },
    'other': True,
}
Parameters
Name Description
field_updates dict

Field names or paths to update and values to update with.
option Optional[WriteOption]

A write option to make assertions / preconditions on the server state of the document before applying changes.
retry google.api_core.retry.Retry

Designation of what errors, if any, should be retried. Defaults to a system-specified policy.
timeout float

The timeout for this request. Defaults to a system-specified value.
Exceptions
Type Description
google.cloud.exceptions.NotFound If the document does not exist.
Returns
Type Description
WriteResult The write result corresponding to the updated document. A write result contains an update_time field.