Cloud Firestore: Can't iterate through all query results

[jlara310]

google-cloud-firestore
Version: 0.29.0
Linux, Python 2.7.13

When you try to iterate over a query result, the generator times out after a while and does not return an error. Query result generator will silently miss results in queries with many documents.

from google.cloud import firestore
db = firestore.Client()
coll_ref = db.collection(u'users')

count = 0
mycoll = db.collection(u'users').get()

for e in mycoll:
    # There are 1000 docs in this collection. Only about 283 get updated. No error message  
    db.collection(u'users').document(e.id).update({
        u'myfield': False
    })
    count += 1
    # time.sleep(.5) the longer this wait is, the fewer docs get updated

print(count)

Issue brought up in this SO post.

[tseaver]

Your example mutates the collection while iterating it, which isn't likely to be safe even for an in-process datastructure like list or dict. This example fetches the collection snapshots first, converting them to document references, and then iterates them, performing the updates:

>>> documents = [snapshot.reference for snapshot in mycoll.get()]
>>> count = 0
>>> for document in documents:
...     document.update({u'myfield': False})
...     count += 1
...     time.sleep(0.01)
>>> count
1000

[jlara310]

Thank you for the prompt reply!

[tseaver]

@jlara310 #6043 is a request to document that Query.get / Collection.get have a time limit on iteration, which explains why making longer calls to time.sleep reduced the number of rows in your example.