[BUG] Backlinks are not populated

Question

[BUG] Backlinks are not populated

sheoak opened this issue 5 months ago · comments

Describe the bug
When creating backlinks, the documentation (to my knowledge) doesn’t show a way to retrieve them immediately.
This has been asked several times in the questions section, but I realized none of them are answered so I post this as an issue now.

Is there a way to populate the backlink, similar to fetch_all_links with Link objects? (see example below)

To Reproduce
Considering the definitions below:

class IdCard(Document):
    ref: Indexed(str, unique=True)
    # Only one owner per id card
    owner: BackLink["Person"] | None = Field(original_field="id_card")

class Person(Document):    
    name: str
    parents: List[Link["Person"]] | None = None
    kids: List[BackLink["Person"]] | None = Field(original_field="parents") 

morticia = Person(name="Morticia")
gomez = Person(name="Gomez")
await morticia.insert()
await gomez.insert()

wednesday = Person(name="Wednesday", parents=[gomez, morticia])
await wednesday.insert()

The following does NOT work:

# If uncommented, AttributeError: 'BackLink' object has no attribute 'id'
# await morticia.fetch_all_links()
# AttributeError: 'BackLink' object has no attribute 'name'
print(morticia.kids[0].name)

This works:

result = await Person.find(Person.name == 'Morticia', fetch_links=True).first_or_none()
print(result.kids[0].name)

Expected behavior
Backlinks should be populated

Roman Right · Answer 1 · Tue Feb 27 2024 06:54:08 GMT+0800 (China Standard Time)

Hi @sheoak , thank you for the issue. I'll check what is going on there and will update you here. It is probably a bug

Maxim · Answer 2 · Fri Mar 01 2024 04:49:53 GMT+0800 (China Standard Time)

Looked at the implementation - fetch_all_links doesn't implement fetching BackLinks. Maybe @roman-right accidently forgot it.

In this case the following happens:

Document.fetch_all_links calls Document.fetch_link for each link

This branch in Document.fetch_link is executed, where ref_obj is of type list[BackLink]

    if isinstance(ref_obj, list) and ref_obj:
        values = await Link.fetch_list(ref_obj, fetch_links=True)
        setattr(self, field, values)

Note that Link.fetch_list is called

it calls Link.repack_links to get linked documents that aren't fetched yet
which tries to get id from the link here and fails, because BackLink doesn't have id

So at the moment you have to use find methods

Renja · Answer 3 · Sat Mar 02 2024 19:58:29 GMT+0800 (China Standard Time)

So at the moment you have to use find methods

I'm not quite sure if this is related, but when I try to find documents that have a BackLink I get an error, that the BackLink field can not be encoded
If you have any ideas how to work around this, please tell me 😉

Error

Traceback (most recent call last):
File "<frozen runpy>", line 198, in _run_module_as_main
File "<frozen runpy>", line 88, in _run_code
File "/home/renja/projects/leaderboard/backend/app/test.py", line 52, in <module>
  asyncio.run(init())
File "/home/renja/.pyenv/versions/3.12.2/lib/python3.12/asyncio/runners.py", line 194, in run
  return runner.run(main)
         ^^^^^^^^^^^^^^^^
File "/home/renja/.pyenv/versions/3.12.2/lib/python3.12/asyncio/runners.py", line 118, in run
  return self._loop.run_until_complete(task)
         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/home/renja/.pyenv/versions/3.12.2/lib/python3.12/asyncio/base_events.py", line 685, in run_until_complete
  return future.result()
         ^^^^^^^^^^^^^^^
File "/home/renja/projects/leaderboard/backend/app/test.py", line 45, in init
  league_entries = await LeagueEntry.find(LeagueEntry.summoner == summoner).to_list()
                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/home/renja/projects/leaderboard/backend/.venv/lib/python3.12/site-packages/beanie/odm/queries/cursor.py", line 72, in to_list
  cursor = self.motor_cursor
           ^^^^^^^^^^^^^^^^^
File "/home/renja/projects/leaderboard/backend/.venv/lib/python3.12/site-packages/beanie/odm/queries/find.py", line 688, in motor_cursor
  filter=self.get_filter_query(),
         ^^^^^^^^^^^^^^^^^^^^^^^
File "/home/renja/projects/leaderboard/backend/.venv/lib/python3.12/site-packages/beanie/odm/queries/find.py", line 106, in get_filter_query
  return Encoder(custom_encoders=self.encoders).encode(
         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/home/renja/projects/leaderboard/backend/.venv/lib/python3.12/site-packages/beanie/odm/utils/encoder.py", line 134, in encode
  return {str(key): self.encode(value) for key, value in obj.items()}
                    ^^^^^^^^^^^^^^^^^^
File "/home/renja/projects/leaderboard/backend/.venv/lib/python3.12/site-packages/beanie/odm/utils/encoder.py", line 127, in encode
  return self._encode_document(obj)
         ^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/home/renja/projects/leaderboard/backend/.venv/lib/python3.12/site-packages/beanie/odm/utils/encoder.py", line 110, in _encode_document
  obj_dict[key] = sub_encoder.encode(value)
                  ^^^^^^^^^^^^^^^^^^^^^^^^^
File "/home/renja/projects/leaderboard/backend/.venv/lib/python3.12/site-packages/beanie/odm/utils/encoder.py", line 136, in encode
  return [self.encode(value) for value in obj]
          ^^^^^^^^^^^^^^^^^^
File "/home/renja/projects/leaderboard/backend/.venv/lib/python3.12/site-packages/beanie/odm/utils/encoder.py", line 138, in encode
  raise ValueError(f"Cannot encode {obj!r}")
ValueError: Cannot encode <beanie.odm.fields.BackLink object at 0x7f6f5b7f7080>

Code

import asyncio
from beanie import init_beanie, Document
from motor.motor_asyncio import AsyncIOMotorClient

from app.models import Summoner, LeagueEntry

async def init():
  client = AsyncIOMotorClient(
      "mongodb://localhost:27017",
  )

  await init_beanie(database=client.test_db, document_models=[Summoner, LeagueEntry])

  summoner = Summoner(
      game_name = "test",
      name = "test",
      platform = "test",
      profile_icon_id = 1,
      puuid = "test",
      summoner_id = "test",
      summoner_level = 1,
      tag_line = "test",
  )

  await summoner.insert()

  league_entry = LeagueEntry(
      league_id="test",
      queue_type="test",
      tier="test",
      rank="test",
      league_points=1,
      wins=1,
      losses=1,
      veteran=False,
      inactive=False,
      fresh_blood=False,
      hot_streak=False,
      summoner=summoner,
  )

  await league_entry.insert()

  # get all league entries of the summoner
  league_entries = await LeagueEntry.find(LeagueEntry.summoner == summoner).to_list()
  print(league_entries)


asyncio.run(init())

Models

import pymongo
from pydantic import BaseModel, Field

from beanie import Document, Link, BackLink


# A summoner can have multiple league entries or none at all
# A league entry is linked to a summoner
class Summoner(Document):
  game_name: str
  name: str
  platform: str
  profile_icon_id: int
  puuid: str
  summoner_id: str
  summoner_level: int
  tag_line: str

  league_entries: list[BackLink["LeagueEntry"]] = Field(original_field="summoner")

  class Settings:
      name = "summoner"
      indexes = [
          [
              ("game_name", pymongo.TEXT),
              ("tag_line", pymongo.TEXT),
              ("platform", pymongo.TEXT),
          ]
      ]


class LeagueEntry(Document):
  league_id: str
  queue_type: str
  tier: str
  rank: str
  league_points: int
  wins: int
  losses: int
  veteran: bool
  inactive: bool
  fresh_blood: bool
  hot_streak: bool

  summoner: Link[Summoner]

  class Settings:
      name = "league_entry"
      indexes = [
          [
              ("tier", pymongo.TEXT),
              ("rank", pymongo.TEXT),
              ("league_points", pymongo.TEXT),
          ]
      ]

Valentin Oliver Loftsson · Answer 4 · Wed Mar 13 2024 02:51:29 GMT+0800 (China Standard Time)

I don't know if this is related, but in Pydantic v2 it seems like the way to define a BackLinks original_field is different from the description in the docs. From reading the source code the following seems to be the way to do it:

class Door(Document):
    house: BackLink[House] = Field(json_schema_extra={"original_field": "door"})

as opposed to

class Door(Document):
    house: BackLink[House] = Field(original_field="door")

sheoak · Answer 5 · Fri Mar 15 2024 15:55:38 GMT+0800 (China Standard Time)

I don't know if this is related, but in Pydantic v2 it seems like the way to define a BackLinks original_field is different from the description in the docs

Yes, and the new format is poorly documented. But it still doesn’t work in my case.

Christoforos Vasilatos · Answer 6 · Sat Mar 16 2024 03:59:11 GMT+0800 (China Standard Time)

Any updates on this?

JOJO · Answer 7 · Mon Mar 18 2024 02:51:39 GMT+0800 (China Standard Time)

Any updates on this? Is there a way on demand fetch one particular BackLink field? Can someone share an example?

Lucas Tieman · Answer 8 · Thu May 09 2024 03:37:02 GMT+0800 (China Standard Time)

Yeah, this is causing issues for us as well, the weird part is that it seems to periodically work. Has any work been done on this?