访问 Datastore 中命名空间的元数据

Question

Is there any way to access metadata of a namespace in Google Cloud Datastore? Im interested in getting something like a created_at property.

In order to find out all provided properties/attributes for a namespace:

ds_client = get_datastore_client(project=PROJECT)

query = ds_client.query(kind="__namespace__")
query.keys_only()
for ns in  query.fetch():
    print(ns)
    print(dir(ns))

Output:

<Entity('__namespace__', 'xxxxx') {}>
['__class__', '__contains__', '__delattr__', '__delitem__', '__dict__', '__dir__',
 '__doc__', '__eq__', '__format__', '__ge__', '__getattribute__', '__getitem__', 
'__gt__', '__hash__', '__init__', '__init_subclass__', '__iter__', '__le__', '__len__', 
'__lt__', '__module__', '__ne__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', 
'__setattr__', '__setitem__', '__sizeof__', '__str__', '__subclasshook__', '__weakref__',
 '_meanings', 'clear', 'copy', 'exclude_from_indexes', 'fromkeys', 'get', 'id', 'items',
 'key', 'keys', 'kind', 'pop', 'popitem', 'setdefault', 'update', 'values']

Nothing seems promising

Answer 1

Namespaces are implicitly created, so there isn't a backing entity for each namespace. Thus there isn't metadata on a namespace. Stats entities Stat_Ns_Total are the closest thing to metadata for namespaces.

The entities from __namespace__ aren't stored entities and are created for the query itself.

Each entity in Firestore in Datastore mode has a version field that's available through the EntityResult , but the python client library strips that away from you:( and only provides an updated time and not a created time.

Answer 2

Firestore in Datastore mode provides access to metadata that includes information about entity groups, namespaces, entity kinds, properties, and property representations for each property. You can use metadata, for example, to build a custom datastore viewer for your application or for backend administrative functions.

You can use a namespace query to find all namespaces used in the application's entities. This allows you to perform activities such as administrative functions across multiple namespaces.

Namespace queries return entities of the special kind __ namespace __ whose key name is the name of a namespace. (An exception is the default namespace designated by the empty string "": since the empty string is not a valid key name, this namespace is keyed with the numeric ID 1 instead.) Queries of this type support filtering only for ranges over the special pseudoproperty __ key __, whose value is the entity's key. The results can be sorted by ascending (but not descending) __ key __ value. Because __ namespace __ entities have no properties, both keys-only and non-keys-only queries return the same information.

For reference you can check with the documentation Datastore Metadata and Namespace queries .