In the new Datastore Mode documentation, there is mention of allocateIds() method. However, beyond a single paragraph, there isn't an example code that illustrates how this method is used.
I am trying to allocate an ID each time I create a new entity so that I can save the ID as a property of the entity itself.
I assume that in pseudocode, it works like this:
user_id = allocateIds(number_id_ids=1)
user_key = datastore_client.key(kind='User', user_id)
user = datastore.Entity(key=user_key)
user.update({ 'user_id': user_id }) # Allows a get_user_by_id() query
datastore_client.put(user)
How exactly does allocateIds() work in practice?
Yes, allocateIds() should work for the case where you want to get an ID from Datastore mode and use it as both an ID and property value:
from google.cloud import datastore
client = datastore.Client()
# Allocate a single ID in kind User
# Returns list of keys
keys = client.allocate_ids(client.key('User'), 1)
# Get key from list
key = keys[0]
print(key.id)
# Create a User entity using our key
user = datastore.Entity(key)
# Add ID as a field
user.update({
'user_id': key.id
})
# Commit to database
client.put(user)
# Query based on full key
query = client.query(kind='User')
query.key_filter(user.key, '=')
results = list(query.fetch())
print(results)
For most other cases where you just want a single auto-ID, you can skip allocate_ids:
# Create a User entity
# Use an incomplete key so Datastore assigns an ID
user = datastore.Entity(client.key('User'))
# Add some data
user.update({
'foo': 'bar'
})
# Datastore allocates an ID when you call client.put
client.put(user)
# user.key now contains an ID
user_id = user.key.id
print(user_id)
# Query with the ID and key
query = client.query(kind='User')
query.key_filter(user.key, '=')
results = list(query.fetch())
print(results)