Class DocumentReference (2.5.2)

Version 2.5.2

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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.

Inheritance

builtins.object > BaseDocumentReference > DocumentReference

Methods

collections

collections(page_size: Optional[int] = None, retry: google.api_core.retry.Retry = <_MethodDefault._DEFAULT_VALUE: <object object>>, timeout: Optional[float] = 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 = <_MethodDefault._DEFAULT_VALUE: <object object>>, timeout: Optional[float] = None)

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: Optional[google.cloud.firestore_v1._helpers.WriteOption] = None, retry: google.api_core.retry.Retry = <_MethodDefault._DEFAULT_VALUE: <object object>>, timeout: Optional[float] = None)

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: Optional[Iterable[str]] = None, transaction=None, retry: google.api_core.retry.Retry = <_MethodDefault._DEFAULT_VALUE: <object object>>, timeout: Optional[float] = None)

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: Callable)

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 = <_MethodDefault._DEFAULT_VALUE: <object object>>, timeout: Optional[float] = None)

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: Optional[google.cloud.firestore_v1._helpers.WriteOption] = None, retry: google.api_core.retry.Retry = <_MethodDefault._DEFAULT_VALUE: <object object>>, timeout: Optional[float] = None)

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,
}

Warning: A field path can only be used as a top-level key in field_updates.

>>> 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.