migrate_chat_data.py

from itertools import islice

import firebase_admin
from firebase_admin import credentials
from firebase_admin import db
from firebase_admin import firestore


def _split(data, size=500):
    """Splits a dictionary into a sequence of smaller dictionaries."""
    it = iter(data)
    for i in range(0, len(data), size):
        yield {k:data[k] for k in islice(it, size)}

def transform_rooms(rooms, members):
    for room_id in rooms:
        member_data = members.get(room_id)
        if member_data:
            rooms[room_id]['members'] = member_data
    return rooms

def transform_messages(messages):
    unwrapped = {}
    for room_id, messages_dict in messages.items():
        for message_id, message in messages_dict.items():
            key = (room_id, message_id)
            unwrapped[key] = message
    return unwrapped
    
def load_rooms(client, rooms):
    rooms_collection = client.collection('rooms')
    for rooms_batch in _split(rooms):
        batch_op = client.batch()
        for room_id, room_data in rooms_batch.items():
            doc = rooms_collection.document(room_id)
            batch_op.set(doc, room_data)
        batch_op.commit()
        
def load_messages(client, messages):
    rooms_collection = client.collection('rooms')
    for messages_batch in _split(messages):
        batch_op = client.batch()
        for ((room_id, msg_id), msg_data) in messages_batch.items():
            doc = rooms_collection.document(room_id).collection('messages').document(msg_id)
            batch_op.set(doc, msg_data)
        batch_op.commit()


if __name__ == '__main__':
  cred = credentials.Certificate('path/to/service_account.json')
  firebase_admin.initialize_app(cred, options={
    'databaseURL': 'https://my-project-id.firebaseio.com'
  })
  
  # Extract
  rooms = db.reference('rooms').get()
  members = db.reference('members').get()
  messages = db.reference('messages').get()

  # Transform
  rooms = transform_rooms(rooms, members)
  messages = transform_messages(messages)

  # Load
  client = firestore.client()
  load_rooms(client, rooms)
  load_messages(client, messages)

What if we want to load a json data file to cloud firestore or RTDB in Firebase?